Results of the Literature Search

The literature search identified 24,870 unique citations. During the title screening, we excluded 15,829 citations. During the abstract screening, we excluded 7,615 citations that met at least one of the exclusion criteria (see Chapter 2 for details). During article screening, we excluded an additional 1,368 articles that did not meet one or more of the inclusion criteria (see Appendix D). Fifty-eight articles describing data from 51 studies were included in the review (Figure 2).

Figure 2 describes the flow of articles through the screening and review process. 22,861 unique articles were identified in the search, 14,448 were screened out at the title level, 7083 were screened out at the abstract level, 1292 were excluded on full text review and 53 articles were included in the report.

Figure 2

Results of the literature search.

We reviewed 3,027 studies registered in ClinicalTrials.gov. No new study met our inclusion criteria for the full text review. No relevant study had results available on ClinicalTrials.gov.

Description of Types of Studies Retrieved

Six studies addressed Key Question 1 (self-management strategies), 14 studies addressed Key Question 2 (dietary strategies), 15 studies addressed Key Question 3 (physical activity strategies), no studies addressed Key Question 4 (orlistat), 21 studies addressed Key Question 5 (combination strategies), and 1 study addressed Key Question 6 (built environment or community level strategies).

Eleven trials and 12 observational studies addressed in 25 articles reported on adults in the general population. A single trial addressed weight maintenance in an obese population. Seven trials reported in 8 articles took place in the workplace, and 2 trials addressed in 2 articles took place in a college setting. Twelve trials reported in 15 articles addressed adult weight maintenance in populations at risk for or with cardiovascular disease or diabetes mellitus. Three trials reported in four articles, and one observational study looked at adult weight maintenance among adults with cancer. Two trials looked at weight maintenance among adults with psychiatric disorders.

We did not identify any study that included exclusively individuals with healthy weight at baseline that met our inclusion criteria. We did not identify any studies addressing prevention of weight gain among socioeconomically disadvantaged individuals that met our inclusion criteria.

Order of the Results

The populations included in the studies and the settings which the strategies occur can affect the generalizability of the results. For this reason, we report the results by population and setting. The most inclusive population (adults in the general population) is reported first, followed by strategies that occur in a specific setting (work based and college based) and finally specific groups with a disease or at risk of a disease (cardiovascular disease, cancer and mental health).

Weight Gain Prevention Among Adults in the General Population

Study Characteristics

Eleven trials (65,562 baseline participants) reported on in 12 articles49-60 and 12 observational studies (414,880 baseline participants)49,56,61-70 were included. The duration of the trials ranged from one 30 minute session56 with followup mailings and phone calls to 144 months of structured visits (Appendix E, Evidence Table 1).51

Most of the trials did not follow participants after the cessation of the intervention.49,51,53-55,57,60 In the three studies that did follow participants after the intervention, the followup after the intervention ranged from 10 to 12 months.56,58,59

The observational studies were sub analyses of participants with available information on weight, diet or physical activity measures from existing cohorts. The maximum duration of followup in the observational studies ranged from 48 to 276 months.63,68,69

Study Characteristics of the Interventional Studies

Ten of the interventional studies were randomized trials of individual participants. One trial compared a media campaign among three communities.50 The stated goal of the intervention in three trials was to prevent weight gain,57,58,60 prevent increase in percent body and abdominal fat in one trial,53 change diet or physical activity patterns in five trials,49,51,54,56,59 improve a cognition score among elderly patients in one trial,55 and reduce the risk of cardiovascular disease in the community wide trial.50

Five trials took place in the United States,49,50,53,57,58 one in Canada,54 two in Europe,55,56 and two in Australia.59,60 In seven trials, participants were recruited from the local community49-51,53,57-59 and from primary care clinics in two trials.54,56 The recruitment source for one trial was the school where the women had children enrolled.60 The recruitment source was not reported in one trial.55

The calendar years of recruitment were reported in six trials. The earliest recruitment year was 197250 and the last recruitment year was 2006.60

Interventions were administered at one location in four trials,55-58 multiple sites in five trials,49,51,53,54,60 by mail in one trial,59 and by a local media campaign combined with mailings in one trial (Appendix E, Evidence Table 1).50

Study Characteristics of the Observational Studies

The 12 observational studies were reported in 10 publications.61-70 One publication reported on three studies.61 One study reported different approaches in two publications,64,65 and two sub cohorts were reported on in separate publications.68,69

The observational studies included a sub analysis from a randomized trial,70 seven prospective cohorts,6 ,63-65,67-69 and two studies followed participants who had participated in a previous cross sectional survey.62,66

Only one prospective study specifically stated that obesity prevention was a goal during the design of the original cohort study.67 Five studies took place in the United States,61,64,65,70 one occurred in Canada,62 three occurred in Europe,66-69 and one took place in the Philippines.63

The earliest recruitment year was 197661 and the most recent recruitment year was 2002 (Appendix E, Evidence Table 1).62

Population Characteristics

Interventional Studies

Sixty nine percent of the randomized participants were included in the analyses relevant to change in BMI, weight, or waist circumference. Inclusion criteria for the trials commonly included household structure, sex, age, or life stage as well as race or ethnicity group (Appendix E, Evidence Table 2).

One trial included only heterosexual couples who began cohabitating within two years of recruitment59 and another trial included households with at least two adults.57 Five trials included only women.49,51,53,58,60 Among the trials that included both sexes, the percent of women ranged from 46 to 57 percent. Age restrictions were present in seven trials.49,51,53-56 ,58 The observed ages at recruitment ranged from 25 to 79 years. The two trials that targeted patients over 65 years old did not report the age of the oldest participants included. The mean ages at recruitment were 70 and 74 years in these two trials.54,55 Two trials included post menopausal women exclusively.49,51 One trial included only women with children aged 5 to 12 years.60 No trial included only participants of a particular race or ethnicity background, but three trials specifically targeted recruitment to include an ethnically diverse population.49,51,53 No trial that occurred outside of the United States reported on race or ethnicity. All of the trials from the United States reported on race. The range of patients of each race or ethnicity group included 50 to 87 percent White, 11 to 28 percent Black, 4 to 16 percent Hispanic, and 0.4 to 12 percent Asian, Native American or Pacific Islander. Educational status was not a requirement for inclusion in any trial, but was reported in eight of the trials.49,51,53-55,57,58,60 The percent of participants with a college degree ranged from 28 to 84 percent (Appendix E, Evidence Table 2).

Trials frequently included participants based on weight. Four trials restricted patients based on weight or BMI,49,53,55,58 of which three trials included only women (Appendix E, Evidence Table 2).49,53,58

The trials restricted to women included one study each of women who were no more than 165 percent of ideal body weight,49 women with a BMI between 21 and 30 kg/m2,58 women with a BMI between 25 and 35 kg/m2,53 and all women that were not underweight.60 Another trial included men and women participants older than 65 years with a BMI between 18 and 32 kg/m2.55 No trial was restricted to participants with a healthy BMI (19 to 24 kg/m2). In the trial that randomized couples, the women had a mean baseline BMI in the healthy range, but the mean BMI of the men was overweight.59 One trial that included participants greater than 65 years of age did not report a baseline value of weight or BMI.55All other trials reported a mean or median baseline BMI in the overweight (BMI 25 to 29 kg/m2) range.49,51,53,54,56-58 Two trials explicitly excluded participants who had recently used a weight loss program.53,58 Another trial required patients to have had a stable body weight over the past year (<10 percent change in weight) (Appendix E, Evidence Table 2).53

Other common inclusion criteria included activity pattern, 53,54,56-58 dietary pattern,49,51health,49,51,53-59 and the likelihood of being adherent to the intervention.49,51,53,57-59 One trial excluded patients who smoked (Appendix E, Evidence Table 2).53

Observational Studies

Forty nine percent of the baseline participants were included in the weight related analyses. Studies were included only if they accounted for losses to followup in analysis, if they had less than 20 percent attrition from baseline or if the study stated that the analyzed participants were similar to those people recruited at baseline. The majority of studies excluded participants at baseline or for the weight analyses if they had cardiovascular disease, cancer, or other chronic diseases. Four studies required participants to work in healthcare,61,70 one study recruited from graduates of a university,67 one recruited women while they were pregnant,63 and three studies were generally inclusive of the source population.66,68,69 Four studies included only women,61,63-65,70 one study included only men,61 and four studies included both men and women.64-69 No other study reported weight based exclusions (Appendix E, Evidence Table 2).

Interventions

No self-management or orlistat interventions were included, while two dietary, four physical activity, and four combination, and one environment level interventions were included. Ten of the 11 studies included a comparison with a one time session, information booklet or no intervention. Three studies compared interventions head to head. The specifics of each intervention are described prior to the results of the appropriate Key Question (Appendix E, Evidence Table 3 and 4).

Approaches

Observational studies did not implement interventions, instead they investigated the impact of lifestyle behaviors performed by individuals as part of their normal routines. To differentiate the behaviors examined in observational studies from those performed among the randomized interventions, we refer to the factors examined in observational studies as approaches.

Six observational studies (5 publications) reported on more than one approach.61-65 The results of these six studies are reported in the relevant Key Questions (1 through 3) as the studies did not pool the effects of combined self-management, diet, or physical activity behaviors on weight outcomes. Three studies reported on a self-management approach, nine studies reported on a dietary approach, and seven studies reported on a physical activity approach. No observational study reported on the effect of orlistat on a weight outcome. One study reported on the environment level approaches of walkability and traffic in neighborhoods (Appendix E, Evidence Table 3 and 4).

Descriptions of the self-management, dietary, and physical activities that were associated with a weight related outcome from observational studies are reported in Table 3.

Table 3. Description of observational exposures studies reporting on the relationship between strategies of interest and weight change.

Table 3

Description of observational exposures studies reporting on the relationship between strategies of interest and weight change.

Outcomes

Key Points

  • BMI. There is low strength of evidence that:
    • A low fat diet intervention was statistically associated with less BMI gain (0.3 units) over 7.5 years, but the difference did not meet the meaningful between group difference threshold.
    • Participants who were taught by their primary care provider to monitor their heart rate during exercise had a greater decrease in BMI than the controls.
    • Household level and couples combination interventions met the meaningful between group differences between the intervention groups and the controls at one year, but neither was statistically significant.
    • Neighborhood walkability did not affect BMI change over 6 years. Traffic was associated with statistically significant weight gain, but the between group difference did not meet the meaningful threshold.
    • There is insufficient strength of evidence for self-management strategies, because no self-management studies were identified.
  • Weight. There is low strength of evidence that:
    • Television viewing of 5 or more hours per day and sleeping fewer than 6 hours per night were statistically associated with weight gain, but did not meet the meaningful between group difference threshold.
    • Two low fat diet interventions resulted in statistically significant differences in weight loss that met meaningful between group difference at 1 year. The difference remained statistically significant but not meaningful at 7.5 years.
    • Food prepared outside of the home was statistically and meaningfully associated with greater weight gain compared with home cooked meals. However, fast food meals were not associated with weight gain prevention in another study.
    • A healthy eating pattern, a high fiber, low fat eating pattern, percent of calories consumed at breakfast, calories from fat, calories from protein and total calories were statistically associated with less weight gain and at the borderline of a meaningful between group difference.
    • Increasing physical activity over time was meaningfully but not statistically associated with less weight gain through 4 years of followup, but not afterwards. Five other physical activity patterns were associated with statistically significant prevention of weight gain, but none met the meaningful between group difference threshold.
    • A combination intervention to prevent weight gain among mothers with young children had a meaningful between group difference and was statistically significant compared with no intervention.
    • A community level media campaign combined with mailed cookbooks and educational pamphlets had a statistically significant difference compared with no community intervention, but did not meet the between group meaningful threshold to prevent weight gain.
  • Waist circumference. There is low strength of evidence that:
    • A low fat diet intervention resulted in statistically significant decrease in waist circumference that met meaningful between group difference at 1 year. The difference was statistically significant but not meaningful at 7.5 years in another study.
    • Neither intervention was favored between the gym based exercise group and the control group in waist circumference among the elderly.
    • There was a meaningful between group difference but not a statistically significant difference between the combination intervention for the mothers of young children and the controls.
    • There is insufficient strength of evidence for self-management strategies, because no self-management studies were identified.
  • Progression to overweight or obesity. There is low strength of evidence that:
    • Eating food outside the home one or more times per week was associated with a 20 to 30 percent increased risk of progressing to overweight or obesity.
    • There is insufficient strength of evidence for self-management, physical activity or built environment strategies, because no studies were identified.
  • Adherence
    • There is low strength of evidence that adherence is poor. Adherence was less than 80 percent in all intervention trials that reported on an adherence outcome.
  • Obesity related clinical outcomes
    • There is insufficient strength of evidence for mortality and quality of life because no studies met our criteria.
  • Adverse effects
    • There is low strength of evidence for mortality outcomes in dietary trials. The intervention group had 0.1 percent less mortality than the controls in a dietary trial.
    • There is low strength of evidence for adverse events in physical activity trials. A physical activity trial reported no difference in adverse events.
    • The strength of evidence is insufficient for all other adverse effect outcomes.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

No trial reported on a self-management intervention. Three trials included a self-management approach as part of a combination intervention as reported with Key Question 5.57-59

Three observational studies, described in one article (289,916 baseline; 120,877 analyzed) reported on daily hours of sleep and television watching in a single publication.61 The results were pooled in the publication's analysis so a meta-analysis was not performed. Weight change was the only outcome of interest reported. The study adjusted for age, baseline BMI, diet, physical activity, alcohol consumption, and cigarette smoking.

BMI Change

No study on self-management strategies and BMI change met our inclusion criteria.

Weight Change

The mean weight gain was 7.6 kg over 20 years of followup. Sleeping 6 to 8 hours per night was statistically associated with less weight gain compared with sleeping less than 6 hours per night, but no sleep duration met the threshold for a meaningful between group difference in weight gain.61 Each hour of television watching was associated with a 0.1 kg increase in weight per 4 year interval of followup. Television viewing did not meet the meaningful between group difference threshold for weight gain, although the finding was statistically significant. Five hours of television viewing per day were required for a 2.5 kg increase in weight over 20 years (Appendix E, Evidence Table 5).61

Waist Circumference Change

No study on self-management strategies and waist circumference change met our inclusion criteria.

Progression to Overweight or Obesity

No study on self-management strategies and progression to overweight or obesity met our inclusion criteria.

Other Outcomes

No adherence, mortality, health related quality of life or adverse effect outcomes were reported in studies of self -management strategies.

Subgroups

The duration of sleep and television viewing findings were similar when the results were examined separately by age, baseline BMI and cohorts of men and women (Appendix E, Evidence Table 5).61 No other subgroups were reported.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

Two trials (51,043 randomized; 42,279 analyzed) reported on dietary interventions,49,51 and eight observational studies (369,191 participants at baseline; 160,878 analyzed)61-66,68,69,71 reported on dietary approaches for preventing weight gain among adults. Three trials included a dietary component as part of a combination intervention as reported with Key Question 5.57-59 The two dietary trials included women exclusively (Table 4).49,51 Both interventions used group sessions to change consumption of fats, fruits, vegetables, and grains. The comparison groups received printed information on nutritional guidelines in both trials. Neither trial's primary goal was weight maintenance or the prevention of weight gain. Because fewer than three trials were identified, meta analyses were not conducted.

Table 4. Description of dietary interventions in studies among adults in the general population.

Table 4

Description of dietary interventions in studies among adults in the general population.

The observational studies reported on individual foods, energy intake, and eating patterns. No dietary approach was included in a meta-analysis because studies did not report on similar dietary exposures. Only one observational study stated that a weight related outcome was a primary goal of the original cohort.67

BMI Change

One dietary trial (48,835 randomized; 41,173 analyzed) reported on BMI change.51 BMI remained within 0.1 units of the baseline in the intervention and control groups at an average of 7.5 years of followup. The BMI increased by 0.3 fewer units (95% CI, 0.5 to 0.1) in the low-fat intervention group compared with the group that received nutritional guidelines after adjustment for age, race/ethnicity, baseline BMI, and changes in dietary and physical activity patterns over time. This finding did not meet the threshold for the between group difference at 7.5 years of followup, despite being statistically significant.

Two observational studies (22,669 baseline; 9,683 analyzed) reported on BMI change.62,67 Eating food prepared outside of the home two or more times per week did not have a meaningful between group difference in BMI (0.1 increase per year; 95% CI 0.4 to 0.1, p<0.001) compared with eating out less often than once per month over 7 years of followup.67 Eating fewer than five servings of fruits and vegetables per day was not statically associated with smaller BMI change over six years (ordinal regression estimate -0.1; 95% CI -0.4 to 0.3) and the between group difference was not reported (Figure 3; Appendix E, Evidence Table 5).67

Figure 3 describes the differences in weight change, waist circumference change, and BMI change among adults in the general population for dietary interventions. Two studies are analyzed for weight at 12, 24, 60, 90, and 108 months; two studies are analyzed for waist circumference ate 12, and 90 months; one study is included for BMI change at 90 months.

Figure 3

Differences in weight change, waist circumference change, and BMI change for dietary interventions compared with nutritional information among adults from the general population. BMI = body mass index; cm = centimeter; kg/m2 = kilogram/meter2; Kg = kilogram (more...)

Weight Change

Two dietary interventions (51,043 randomized; 42,279 analyzed) reported on weight change (Figure 3).49,51 Weight decreased in the intervention and nutritional guidelines groups in both trials. The low-fat diet combined with increased fruits, vegetables and grains intervention met the between group difference threshold at 1 year. The intervention group lost 2.2 kg compared with a 0.3 kg increase in weight among the nutritional guidelines group (p<0.05).49 In another study, at 1 year, the low-fat diet group lost 2.2 kg compared with no weight change among the nutritional guidelines group (p<0.001).51 However, the meaningful between group difference was not maintained beyond one year. After a mean of 7.5 years of following the diet, the intervention group weighed 0.7 kg (95% CI 0.5 to 0.9, p<0.01) less than the nutrition guidelines group after adjustment for age, race/ethnicity, baseline BMI, and changes in dietary and physical activity patterns over time.51

Eight observational studies (369,191 participants at baseline; 160,878 analyzed) reported on weight change over 4 to 23 years of followup.61,63-69 Weight increased by around 0.5 kg per year in most studies. The longest study reported a 10 kg increase over 23 years of followup.63 A variety of dietary approaches were reported on including number of meals eaten outside the home,67 fast food eaten outside the home,65 percent of total calories from fat,64 percent of calories from protein,63 percent of intake consumed at breakfast,69 high fiber/low fat dietary pattern,68 healthy eating pattern based on specific foods consumed61 and fruit and vegetable intake.66

The publication that pooled the results of the three largest studies reported a statistically significant and borderline meaningful between group finding for absolute weight gain.61 The least healthy eaters (those in the bottom quintile) gained 1.8 more kilograms per 4 year period (95% CI, 1.3 to 2.3 kg) than the healthiest eaters (those in the top quintile) after accounting for confounders.61 The second through fourth quintiles also gained more weight than the healthiest eaters. All dietary factors examined, except cheese, whole fat milk and low fat or skim milk, were statistically associated with weight change gain after adjustment for age, baseline BMI, and sleep.61 No individual food was associated with a meaningful between group increase in weight. The foods associated with at least 0.5 kg change in weight over 4 years included French fried potatoes (1.52 kg increase per 4 years; 95% CI 1.0 to 2.0 kg) and potato chips (0.8 kg increase per 4 years; 95% CI 0.6 to 1.0 kg).

Two observational studies (20,293 baseline; 9,388 analyzed) reported weight gain according to a threshold.66,67 One study reported on fruit and vegetable consumption and the other reported on eating meals prepared outside the home. Eating more than 698g/day of fruits and vegetables compared with eating less than 362/g day was associated with 74 percent decreased odds of gaining the mean gain of 3.4 kg or more over a 10 year period (OR 0.26, 95% CI, 0.07 to 0.97).66 Greater vegetable consumption had a stronger association (OR 0.18, 95% CI, 0.05 to 0.3; highest compared with the lowest quintile of vegetable consumption) than fruit consumption (OR 0.62, 95% CI, 0.18 to 2.10; highest compared with the lowest quintile of fruit consumption) (Appendix E, Evidence Table 5). Eating meals outside the home was associated with a 10 to 40 percent increased odds of gaining 2 kg or more per year after adjustment for confounders (OR eating out 1 time per week 1.1; 95% CI 0.9 to 1.4; OR eating out 2 or more times per week 1.4; 95% CI 1.1 to 1.6, p for trend=0.001), although those who ate out 2 or more times per week gained only 0.1 kg per year on average (95% CI 0.06 to 0.2) compared with those who rarely ate food outside the home.67

Protein intake, as a percent of total energy consumption, was associated with a statistically significant difference in weight gain over 8 years, but the 0.04 kg weight gained (95% CI 0.03 to 0.06 kg) per percent of energy from protein did not meet the threshold for the between group difference.63 The analysis of total energy intake was also statistically significant but did not meet the threshold for a meaningful difference (1.8 kg gain over 8 years per kilojoule per day; 95% CI 1.3 to 2.3 kg).63 Similarly, calories from fat were associated with a statistically significant weight gain over 7 years (0.02 kg gain per percent; 95% CI 0.001 to 0.05) but did not meet the meaningful threshold.64 Another publication from this cohort reported a statistically significant association between eating fast food three times per week (2.2 kg gained over 15 years among blacks p=0.001, 1.6 kg gained among whites p=0.006), but the difference did not meet the meaningful between group difference threshold.65

Participants at different sites of the same cohort were reported in two studies. Persons in the highest quintile of high fiber/low fat dietary pattern had less weight gain (0.01 kg/year) compared with individuals in the lowest quintile (0.12 kg/year gain).68 This finding was statistically significant (p<0.0001 for trend), but did not meet the meaningful threshold.68 Another site of the cohort reported on the percentage of daily energy consumed at breakfast.69 For each percentage of daily energy intake consumed at breakfast, there was 0.02 kg less gain over the 3.7 mean years of followup (95% CI 0.007 to 0.04 kg less gain). The finding was statistically significant, but did not meet the meaningful threshold.69

Waist Circumference Change

Two dietary interventions (51,043 randomized; 16,597 analyzed) reported on waist circumference change (Figure 3).49,51 The low fat combined with increasing fruits, vegetables and grains diet met meaningful between group difference threshold at one year.49 The intervention group had a 2 cm decrease in waist circumference compared with no change in the nutrition guidelines group (p<0.05).49 In the study with 7.5 years of followup, the low fat diet group had a waist circumference 0.3 cm smaller (95% CI 0.1 to 0.5 cm less) than the nutritional guidelines group at the end of the study.51 The 7.5 year study was statistically significant, but did not meet the meaningful between group difference threshold.

Progression to Overweight or Obesity

No dietary interventions and one observational study (18,494 baseline; 6,574 analyzed) reported on this outcome.67 The percent of the population with a healthy weight (BMI 19 to 24 kg/m2) at baseline was 72 percent of those analyzed. The study of university graduates reported that eating one meal a week outside the home was associated with a 22 percent increased risk of overweight or obesity compared with eating 3 or fewer meals per month outside the home (Hazard Ratio [HR] 1.2, 95% CI, 1.0 to 1.5) after adjustment for age, sex, baseline BMI, education, physical activity, snacking, fiber, alcohol, total energy intake, specialty diets, and smoking.67 The risk increased to 33 percent when two or more meals were consumed outside the home per week (HR 1.3, 95% CI, 1.1 to 1.6, p for trend <0.001) (Appendix E, Evidence Table 5).

Mortality

One dietary intervention (48,835 randomized; 46,856 analyzed) reported on mortality.51 There was no meaningful difference in mortality between the intervention and nutrition guidelines groups (4.5 percent compared with 4.4 percent). (Appendix E, Evidence Table 5).

Subgroups Reported in Interventional Studies

One dietary trial reported on subgroups of interest.49,51 Similar patterns to the main weight change results were observed when women were stratified by age, baseline BMI, malignancy and diabetes at baseline (Appendix E, Evidence Table 5).51

Sex Subgroups in Observational Studies

Six observational studies (366,704 baseline; 165,687 analyzed) 61,64,65,67-69 reported on the relationship between diet and weight measures by sex. The results were similar to the main analyses (Appendix E, Evidence Table 5).

Age Subgroups in Observational Studies

Five observational studies (320,791 baseline; 148,863 analyzed)61,63,68 reported on the relationship between diet and weight measures by age. The results were similar to the main analyses (Appendix E, Evidence Table 5).

Ethnicity Subgroups in Observational Studies

One observational study (5,115 baseline; 3,906 analyzed) reported no diet by ethnicity interactions.64,65

Baseline Weight Subgroups in Observational Studies

Five observational studies (348,210 baseline; 156,505 analyzed) reported on the effects of dietary approaches on change in weight by baseline weight.61,64,65,68,69 The results were similar to the main analyses in three of the studies. Two studies noted that among those individuals who were overweight at baseline, there was a stronger relationship between dietary choices and weight gain than among the individuals who were a healthy weight at baseline. (Appendix E, Evidence Table 5).61,64

Socioeconomic Status Subgroups in Observational Studies

One observational study (25,631 baseline; 6,764 analyzed) reported on the percent of daily energy intake consumed at breakfast by social class.69 No differences were reported.

Chronic Disease Subgroups in Observational Studies

One observational study (18,494 baseline; 9,182 analyzed)67 reported on the relationship between diet and weight measures by chronic disease. No differences from the main analyses were observed (Appendix E, Evidence Table 5).

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

Four trials (828 randomized; 730 analyzed) reported on physical activity interventions53-56 and seven observational studies (342,409 baseline; 162,390 analyzed) reported on physical activity approaches to prevent weight gain among adults.61-64 ,70 Three trials included a physical activity component as part of a combination intervention as reported with Key Question 5.57-59

Two physical activity interventions randomized patients to a supervised exercise program in a community gym compared with educational materials (Table 5).53,55 The other two studies took place within primary care practices.54,56 One study trained physicians to educate their patients about an ideal heart rate and evaluated that heart rate at followup visits compared with no heart rate assessment.54 The other primary care based study randomized patients to a healthy walking program compared with a single educational session.56 Three of the four studies specifically excluded patients who regularly participated in an exercise program.53,54,56

Table 5. Description of physical activity interventions in studies among adults in the general population.

Table 5

Description of physical activity interventions in studies among adults in the general population.

Observational study approaches included the change in duration of a treadmill test at baseline and 7 years of followup,64 categories of physical activity in MET hours per week,61,62,70 and occupational physical activity.63

No study's primary goal was weight maintenance. Because fewer than three studies were identified with a common intervention, meta analyses were not conducted.

BMI Change

Four physical activity interventions (828 randomized; 687 analyzed) and one observational study (4,175 at baseline; 500 analyzed) reported on BMI change (Figure 4).53-56 Most participants lost or maintained weight over the 1 to 2 years of followup.

Figure 4 describes the differences in weight change, and BMI change among adults in the general population for physical activity interventions. Four studies analyze BMI at 12 and 24 months; one study is included in weight change at 12 and 24 months.

Figure 4

Differences in weight change, waist circumference change, and BMI change for physical activity interventions among adults from the general population. BMI = body mass index; kg/m2 = kilogram/meter2; Kg = kilogram; No difference = reported no difference (more...)

One trial found a meaningful and statistically significant effect of the intervention among a population of individuals older than 65 years of age who did not already follow an exercise training program and attended a primary care clinic in Canada. The heart rate training program group lost 1.5 units of BMI more than the physician advice only group, although both groups had a reduction in BMI during the 1 year study period (Appendix E, Evidence Table 5).54

Three trials found no meaningful between group differences or statistically significant differences in BMI change in the gym based or health walks group compared with the educational materials or no intervention control group.53,55,56 The observational study found no statistical difference in activity levels with change in BMI in ordinal regression estimates.62 The between group differences were not reported in the observational study.62

Weight Change

One physical activity intervention (164 randomized; 138 analyzed) reported on weight change.53 There was no statistical or meaningful between group difference at year 1 or year 2 between the strength training and brochure groups.53

Six observational studies (338,234 baseline; 161,890 analyzed) reported on physical activity approaches and weight change.61,63,64,70 In the followup study of one trial, participants maintained weight within 3 kg over 13 years.70 In the other observational studies, about 0.5 kg per year was gained over the course of followup. Physical activity was associated with a meaningful (but not statistically significant) decrease in weight gain in one of the six studies,70although the difference was statistically significant (but did not meet the meaningful between group difference) in five.61,63,64

Participants who were not able to perform a treadmill test for the same duration as baseline had a 2 kg increase in weight over seven years for each minute of decrease in exercise test duration.64 In the publication reporting on three studies, people who increased their physical activity over time (increased activity 23.2 MET hours/week over 4 years) had less weight gain (0.8 fewer kilograms gained over 4 years, 95% CI, 0.6 to less than 1 kg) than those who decreased their activity over time (decrease of 16.3 MET hours/week).61 Although the change in physical activity was statistically associated with weight gain, the change did not meet the between group difference threshold for 4 years of followup.

One of the studies that did not report a meaningful between group finding and had insufficient information to identify statistically significant findings in absolute weight change characterized the physical activity pattern of the women who successfully maintained healthy weight.70 Women who had a healthy BMI at baseline and gained fewer than 2.3 kg at any time point increased their MET hours per week from 17.6 at baseline to 26.1 MET hours per week at 12 years (Figure 4; Appendix E, Evidence Table 5).70 This finding met the between group threshold through 4 years of followup, but not thereafter.70

Women who performed moderate or heavy work had statistically significant weight loss compared with an unknown reference group (moderate work 1.2 kg weight loss over 8 survey years; 95% CI 0.8 to 1.6 kg loss; heavy work 0.8 kg weight loss; 95% CI 0.4 to 1.3 kg loss), but the findings did not meet the 8 year threshold for a meaningful between group difference.63

Waist Circumference Change

One physical activity intervention (120 randomized; 120 analyzed) reported on waist circumference change.55 Three times weekly endurance exercise training among the elderly produced no significant changes in waist circumference compared with the control (Figure 4; Appendix E, Evidence Table 5).55 Quantitative results of means or statistical significance were not reported.

Progression to Overweight or Obesity

No study on physical activity interventions and progression to overweight or obesity met our inclusion criteria.

Other Outcomes

Four physical activity interventions (828 randomized; 687 analyzed) reported on at least one other outcome. One trial reported that no serious adverse events occurred during the trial, although they do not mention what events would have been considered serious.54 Adherence or compliance with the intervention was reported in all four trials. Adherence with the interventions ranged from 33 percent (participated in at least one heart walk)56 to 71 percent in two interventions (three or more exercise sessions per week with heart monitoring54 and performing strength training at least twice weekly53) (Appendix E, Evidence Table 5).

Subgroups

No subgroups were reported in the interventional studies. Five of the six observational studies (334,907 baseline; 158,862 analyzed) reported on subgroups (Appendix E, Evidence Table 5).

Sex Subgroups in Observational Studies

Sex did not modify the main findings in three studies (Appendix E, Evidence Table 5).61

Age Subgroups in Observational Studies

In one study, pre menopausal women and those under age 65 had greater absolute weight gain with decreased physical activity compared with menopausal and older women.70 The publication reporting three studies reported no difference from the main analyses in the physical activity weight gain relationship when stratified by age (Appendix E, Evidence Table 5).61

Ethnicity Subgroups in Observational Studies

No study on race or ethnicity subgroups and physical activity met our inclusion criteria.

Baseline Weight Subgroups in Observational Studies

In four studies, participants who were overweight at baseline had a greater increase in weight with decreased fitness than people who were healthy weight at baseline.61,64 Another study found that healthy weight individuals had greater weight gain with decreased physical activity than the overweight and obese women (Appendix E, Evidence Table 5).70

Smoking Subgroups in Observational Studies

One study reported no physical activity by smoking interaction (Appendix E, Evidence Table 5).70

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No study on the use of orlistat and weight maintenance among a general population of adults met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of a combination of self-management, dietary, physical activity, and medication strategies for the prevention of weight gain among adults?

Four trials (988 randomized; 750 analyzed) reported on a combination of self-management, dietary, and physical activity interventions.57-60

The four randomized combination interventions differed in their target populations and interventions (Table 6). One study which aimed to prevent weight gain randomized healthy weight and overweight women of childbearing age . Another study randomized healthy weight, overweight and obese women with a young children to prevent weight gain.60In another trial, the intervention groups received self monitoring, dietary, and physical activity strategies over the phone and in group sessions or through the mail and were compared with a control group that received an informational booklet.58 Another study randomized couples who had lived together for two years or less to in person and mail, mail only, or no intervention to promote healthy diet and physical activity behaviors.58 A third study randomized households that included at least two adults and a child to a control group or group sessions, phone calls, and a newsletter to change individual and household self monitoring (daily weighing and television viewing), as well as dietary and physical activity behaviors. Information on children is not included in the results below.57 Two studies' goals included the prevention of weight gain.57,58 The differences in study populations prevented meta analyses.

Table 6. Description of combination interventions in studies among adults in the general population.

Table 6

Description of combination interventions in studies among adults in the general population.

BMI Change

Three combination interventions (738 randomized; 535 analyzed) reported on BMI change.57-59 The couples59 and households57 interventions met the between group difference at one year, but were not statistically significant. There was no statistical or meaningful between group difference in the trial designed to prevent weight gain among women (p=0.39) (Figure 5; Appendix E, Evidence Table 5).

Figure 5 describes the differences in weight change, waist circumference change, and BMI change among adults in the general population for dietary interventions. Three studies analyzeBMI at 12 and 36 months; two studies analyze wasit circumference at 12 months, and two studies analyze weight at 12 and 36 months.

Figure 5

Differences in weight change, waist circumference change, and BMI change for combination interventions among adults from the general population. BMI = body mass index; cm = centimeter; kg/m2 = kilogram/meter2; Kg: kilogram; PA = Physical activity; SM (more...)

Weight Change

Two combination interventions (534 randomized; 420 analyzed) reported on weight change.58,60 Among the trial designed to prevent weight gain among 25 to 45 year olds, there was no statistical or meaningful difference between groups at one year (Figure 5; Appendix E, Evidence Table 5).58 In the trial that recruited mothers with young children, those in the lifestyle intervention group lost 0.2 kg at one year, compared with a 0.8 kg gain in the control group (1.1 kg; 95% CI 0.2 to 2.0 less weight gain).60

Waist Circumference Change

Two combination interventions (524 randomized; 370 analyzed) reported on waist circumference change.59,60 The mothers with young children who received the intervention lost 1.3 cm in waist circumference compared with a 0.1 cm gain in the control group over one year, although the baseline weight adjusted decrease was not statistically significant (-1.5 cm; 95% CI -4.0 to 1.0).60There was no statistical or between group difference in the couples intervention.59 (Figure 5; Appendix E, Evidence Table 5).

Progression to Overweight or Obesity

Two combination interventions (558 randomized; 361 analyzed) reported on progression to overweight or obesity.58,59 In the couple study, compared with the prevalence of overweight or obesity at baseline (61 percent of men and 28 percent of women), the respective percent increases in overweight and obesity at 16 months were 8 percent and 3 percent in the controls, 7 percent and 2 percent in the group that received mailings, and 2 percent and 2 percent in those who received mailings and participated in contact sessions.59 In the trial of women aged 25 to 45 years old, 40 percent of women remained within 2 kg of their baseline body weight, while 60 percent gained 2 kg or more during the 3 year study period. There was no statistical difference by intervention group (p=0.26) (Appendix E, Evidence Table 5).58

Adherence

Two combination interventions (464 randomized; 379 analyzed) reported on adherence. The study of 25 to 45 year old women reported 50 percent attendance across 15 sessions over 24 months.58 In the household study, 73 percent of households attended at least four of five group sessions and completed at least half of the home based activities over 1 year. Twenty percent attended all group sessions and completed 100 percent of the household activities (Appendix E, Evidence Table 5).57

Other Outcomes

No studies reported on mortality, health related quality of life or adverse effect outcomes.

Subgroups

The study of couples reported no differences in the effect of the intervention by sex.59 The study of 25 to 45 year old women reported no differences in weight gain by intervention when they stratified by women who were healthy weight versus overweight at baseline.58 The study of women with young children reported that women under 40 with a BMI of 18 to 24 kg/m2 at baseline who received the intervention lost 0.7 kg compared with a weight gain of 1.7 kg in the control group. This 2.4 kg difference is over one kilogram greater than the weight difference observed in the analysis including individuals with any baseline BMI (Appendix E, Evidence Table 5).

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

One interventional study (41,958 individuals in the community; 2,151 recruited at baseline; 1,294 analyzed)50 and one observational study (3,174 at baseline; 500 analyzed)62 were included (Appendix E, Evidence Table 5). The interventional study included three demographically similar communities in Northern California. A multi stage random sample of the communities were recruited in 1972 and followed through 1975. Two communities received interventions and another community did not.50

The two intervention communities had billboard, newspaper, radio, and television advertising with information on cardiovascular disease risk factors and how to reduce them (Table 7).50 The individuals recruited for outcome assessment also received pamphlets, cookbooks and other information through the mail (Table 7; Appendix E, Evidence Table 7). The comparison community did not receive a mass media campaign. The goal of the study was to reduce the risk of cardiovascular disease (Appendix E, Evidence Table 5).50

Table 7. Description of interventions in studies among adult populations using environmental strategies.

Table 7

Description of interventions in studies among adult populations using environmental strategies.

The observational study was a six year longitudinal assessment of neighborhood walkability in Canada (Appendix E, Evidence Table 5).62 Neighborhood walkability was measured using Geographic Information Systems (GIS) data from the 2001 and 2006 censuses.62 This index incorporated assessments of the density of dwellings, land use mix, and intersections. The index was categorized as lowest, low, mid, high, and highest walkability. Traffic was measured by survey responses from a question assessing whether traffic decreased walkability (Appendix E, Evidence Table 5).

BMI Change

The interventional study did not report on BMI change. The between group differences in BMI change by neighborhood walkability or traffic perception were not reported (Appendix E, Evidence Table 8).62 The ordinal regression estimate for traffic was statistically significant for an increase in BMI (ordinal regression estimate 0.2; 95% CI 0.1 to 0.4). The estimates for walkability were not statistically significant.62

Weight Change

The community based study calculated “relative weight,” defined as actual weight divided by ideal weight, and evaluated percent change in relative weight as their outcome.50 The control community demonstrated a slight increase in relative weight (0.3 percent) versus no change in relative weight among both intervention communities. The baseline weight was not reported per group, so we cannot determine if the between group difference was met. The difference between the two intervention communities and the control was statistically significant (p=0.04).

The observational study did not report on weight change (Appendix E, Evidence Table 8).

Waist Circumference Change

No study on environmental level strategies and their impact on waist circumference change met our inclusion criteria.

Progression to Overweight or Obesity

No study on environmental level strategies and their impact on the progression to overweight or obesity met our inclusion criteria.

Other Outcomes

No studies reported on adherence, mortality, health related quality of life or adverse effects.

Subgroups

The community based study examined subgroups of patients at high risk for cardiovascular disease.50 This subgroup analysis contained four groups: community 1 received no intervention (group 1; n=95), community 2 received the mass media campaign (group 2; n=94), community 3 received the mass media campaign (group 3; n=40), and community 4 received the mass media campaign and individual level counseling (group 4; n=77). Communities 1 to 3 had a 1 percent decrease in relative weight at 2 years, while Community 4 had a 1.5 percent decrease. There was no clinically or statistically significant difference between groups (Appendix E, Evidence Table 8). No other subgroups were reported.

Weight Gain Prevention Among Obese Adults

Study Characteristics

One trial was identified (124 randomized; 120 analyzed).72 Abdominally obese women were recruited from a Swedish newspaper in 2005. The goal of the study was to increase bicycling as a mode of commuting to work. Additionally, the study aimed to increase the average kilometers biked per day and steps walked. The study stated that anthropometric measures were not a goal of the study and that the study was not powered to detect differences between groups over the 18 month intervention period (Appendix E, Evidence Table 6).

Population Characteristics

Abdominally obese women (waist circumference 88 to 120 cm) aged 30 to 60 years old who worked at least 3 days per week outside the home were included after passing a health exam by a physician to identify contraindications to physical activity. Only women who were receptive to behavior change were included (Appendix E, Evidence Table 7).72

Interventions

Participants in the bicycling and walking group were randomized to individual group sessions with a physician to increase physical activity with an emphasis on bicycling and walking (baseline, 6 and 12 months), 2 group sessions (2 and 14 months), and given a new bicycle. The walking group was given a pedometer, encouraged to increase walking and participated in 2 group sessions (baseline and 6 months).72 All participants were followed for 18 months after baseline (Appendix E, Evidence Table 8).

Outcomes

Key Points

  • BMI change
    • There is insufficient strength of evidence because no studies were identified.
  • Weight change
    • There is low strength of evidence that neither behavior was favored to prevent weight gain between bicycle riding to work among women compared with increasing walking to work.
  • Waist circumference change
    • There is low strength of evidence that neither behavior was favored to prevent waist circumference increases between bicycle riding to work among women compared with increasing walking to work.
  • Adherence
    • There is insufficient strength of evidence because no studies were identified.
  • Mortality, health related quality of life and adverse events
    • There is insufficient strength of evidence because no studies were identified.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of self-management strategies and weight maintenance of obese adults met our inclusion criteria.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of dietary strategies and weight maintenance among obese adults met our inclusion criteria.

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

One trial (124 randomized; 120 analyzed) reported on two physical activity interventions to prevent weight gain.72

BMI Change

The study did not report on physical activity and BMI change.

Weight Change

There was no meaningful between group or statistical difference in weight change between the bicycling combined with walking group (0.4 kg lost from baseline; 95% CI -1.6 to 0.7 kg) compared with the walking group (0.3 kg lost from baseline; 95% CI -1.2 to 0.7 kg) at 18 months (Appendix E, Evidence Table 9).72

Waist Circumference Change

There was no meaningful between group difference in waist circumference change between the bicycling combined with walking group (-2.1 cm decrease from baseline; 95% CI -3.4 to -0.8 cm) compared with the walking group (-2.6 cm decrease from baseline; 95% CI -4.0 to -1.2 cm) at 18 months.72 The study did not report the statistical significance for the difference between the groups, but stated that there was a similar reduction in both groups (Appendix E, Evidence Table 9).

Progression to Overweight or Obesity

All women were abdominally obese at baseline. Further progression of obesity was not reported.

Other Outcomes

The study did not report on physical activity and adherence, mortality, health related quality of life or adverse effects.

Subgroups

The study did not report on physical activity and subgroups.

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No study on the use of orlistat and weight maintenance among obese adults met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of combination strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of combination strategies and weight maintenance among obese adults met our inclusion criteria.

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of environment level strategies and weight maintenance among obese adults met our inclusion criteria.

Weight Gain Prevention Among Adults in Work-Based Settings

Study Characteristics

Seven trials (76,310 participants) took place in work settings. The results from these trials were reported in eight articles. Both recruitment and the intervention occurred in the workplace.73-79 One trial occurred in the military (124,367 eligible active duty air force members; 68,591 members analyzed), which we considered a workplace.73 One trial occurred at sites within a chemical company (10,281 eligible employees; 3,152 employees recruited at baseline; 3,119 analyzed);75,80 another occurred in hospitals (1,983 employees randomly selected; 806 recruited at baseline; 731 analyzed),76 and the other trials occurred at a variety of work sites.74,77-79 All seven of the work based interventional studies were multicenter trials. Four trials were randomized,76-79 the other three used non randomized, quasi experimental designs or randomized by site rather than by individual (Appendix E, Evidence Table 10).73-75

The duration of the interventions ranged from 12 to 24 months. The earliest year of recruitment was 2002,73 and the latest year of recruitment was 2008 (Appendix E, Evidence Table 10).78

Four studies were done in the United States73,75-77 and three in Europe (Appendix E, Evidence Table 10).74,78,79

Four studies stated their goals were to prevent or reduce weight gain.73,74,76,77 while the other studies' goals were to increase physical activity,78 to improve cardiovascular risk factors,79 and to prevent obesity (Appendix E, Evidence Table 10).75,80

Population Characteristics

Inclusion criteria varied between the seven work based trials. The number of women that were included in each study varied considerably between studies depending on the workplace. Women were less than 15 percent of the military study population and 30 percent of the chemical company study population.73,75 A population of hospital workers was more than 75 percent women (Appendix E, Evidence Table 11).76

The mean age of participants that were included in each study also reflected the age distribution of that worksite. For example, mean age was in the early thirties for the military population73 and in the mid forties for the chemical company population.75 In a sample of employees from a variety of worksites in the Netherlands, the mean age was in the upper thirties.74 Race/ethnicity, education, and smoking status were not consistently reported across studies (Appendix E, Evidence Table 11).

Interventions

All work based trials used a combination of strategies including self management (n=4)73,74,77,78, diet (n=5)73,75,76,79-81, and physical activity (n=6)73,75-80. Five of the work based interventions also included specific environmental changes as a part of their combination strategy.74-78 The specifics of each intervention are described prior to the results by Key Question (Table 8; Appendix E, Evidence Table 12).

Table 8. Description of interventions in studies among adult populations in work settings.

Table 8

Description of interventions in studies among adult populations in work settings.

Outcomes

Key Points

  • BMI
    • The strength of evidence is low that work based combination interventions that use diet, physical activity, and environmental components prevent adult BMI gain. A single work based intervention that combined diet, physical activity and environmental components resulted in meaningful and statistically significant prevention of BMI change at 12 months; however, four other work based combination interventions resulted in BMI gain or no difference in BMI as compared with control.
    • No studies evaluated self-management, diet, physical activity, medication, or environmental interventions alone in the work setting.
  • Weight
    • The strength of evidence is moderate that work based combination interventions that use either diet, physical activity, and environmental components or internet-based diet and physical activity counseling prevent adult weight gain. One work based intervention that combined diet, physical activity and environmental components resulted in meaningful and statistically significant prevention of BMI change at 12 months and another work based intervention that combined internet-based diet and physical activity counseling results in meaningful and statistically significant weight gain prevention at 24 months. However, one other work based combination intervention resulted in no difference in weight as compared with control.
    • There is insufficient evidence that self-management, diet, physical activity, medication, or environmental interventions alone in the work setting prevent weight gain in adults.
  • Waist circumference
    • The strength of evidence is low that work based combination interventions that use self-management and environmental components prevent adult waist circumference increase. A single work based intervention that combined self-management and environmental components resulted in meaningful and statistically significant prevention of waist circumference increase at 12 months; however, another work based combination intervention resulted in no difference in waist circumference as compared with control.
    • There is insufficient evidence that self-management, diet, physical activity, medication, or environmental interventions alone in the work setting prevent waist circumference increase in adults.
  • Adherence
    • There is low strength of evidence that participants have poor adherence to work based combination interventions. We identified few studies that assessed adherence among work based combination interventions, and those studies that did assess adherence did not evaluate similar outcomes. Two studies assessed participation in the intervention, which was variable and low overall. Another study evaluated awareness of and adherence to environmental components of the intervention, which was variable and poor for some aspects of the environmental component.
  • Other outcomes
    • There is insufficient evidence on the influence of work based combination interventions on other outcomes, because no studies met our inclusion criteria.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of self-management strategies and weight maintenance among adults in a work based setting met our inclusion criteria.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of dietary strategies and weight maintenance among adults in a work based setting met our inclusion criteria.

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of physical activity strategies and weight maintenance among adults in a work based setting met our inclusion criteria.

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No study on the use of orlistat and weight maintenance among adults in a work based setting met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of a combination of self-management, dietary, physical activity and medication strategies for the prevention of weight gain among adults?

All work based strategies for weight management used a combination of strategies, including self-management, diet, and physical activity. In addition to these individual level interventions, the majority of work-based combination strategies also included environment level interventions.

The work based trial in the setting of a U.S. chemical company evaluated the effectiveness of site specific environmental changes to promote healthy eating and physical activity in combination with a workplace health promotion program that provided individually tailored programming on self management, diet, and exercise.75,80 The study considered this worksite health promotion program as usual care, as it was in place at both the control and intervention sites. The environmental changes were considered the intervention.

The work based trial in U.S. hospitals evaluated the effects of a combined individual and environment level program.76 Environment level changes included promotional materials and group events to promote healthy eating and physical activity, along with individual level education on diet and exercise through displays, workshops, and newsletters. The control group for this study received no intervention.

Another work based trial in the U.S. occurred in a variety of workplaces.77 This intervention used a combination of self-management, diet, and physical activity interventions, as well as environmental level interventions. Participants were encouraged to self-weigh, received healthy eating newsletters, and received pedometers. Environment level strategies focused on modifying the food and physical activity environments, which included increased availability and decreased price of healthy foods, formation of walking groups, and motivational materials to promote stair use.

There were two work based trials that were implemented in a variety of worksites in the Netherlands.74,79 One combined individual level self-management interventions with environmental level changes.74 The self-management intervention emphasized education, skills training, goal setting, and self monitoring with respect to energy balance, which was supported via a web based tool. The environmental changes implemented varied between worksites. Each intervention was selected and implemented by key personnel at each site. The control group received no intervention. The other work based intervention in the Netherlands combined individual diet and exercise counseling.79 This study did not include an environmental component. The counseling was provided either by telephone or Internet by four trained counselors.

The work based trial based in the United Kingdom was also implemented in a variety of work settings.78 This intervention combined individual level and environment level approaches. On the individual level, the intervention focused on self-management and physical activity education. The environmental changes include posters and team challenges targeting exercise.

The work based trial in the military evaluated the effects of a self-management intervention that included completion of two personal energy plan workbooks supplemented with weekly educational emails on healthy eating habits and physical activity.73 This study did not include an environmental component. The control group in this study received no intervention.

BMI Change

Five trials evaluated change in BMI at 12 and 24 months.74-78,80 Using our predefined criteria for BMI change of 0.2 kg/m2 over 12 months, one study met our between group difference threshold and was statistically significant80. This intervention included individual level diet and physical activity along with an environmental component. This study also resulted in statistically significant prevention of BMI gain at 24 months.75 Three other interventions demonstrated no significant difference between intervention and control,74,76,77 and one intervention resulted in a statistically significant and meaningful BMI increase of 0.2 kg/m2 over 12 months.78 (Figure 6; Appendix E, Evidence Table 13).

Figure 6 describes the differences in BMI among adults in a work setting for combination interventions in five studies at 12 and 24 months.

Figure 6

Differences in BMI change for combination interventions among adults in a work setting. BMI = body mass index; kg/m2 = kilogram/meter2; NR = not reported If the study did not report an estimate of variability, no confidence intervals were generated.

Weight Change

Four trials reported on weight change.73-75,79,80 Using our predefined criteria for weight change of 0.5 kg over 12 months, one study met our between group difference threshold and was statistically significant.80 This intervention included individual level diet and physical activity along with an environmental component. This study also resulted in statistically significant prevention of weight gain at 24 months.75 In another study, one group that used Internet-based diet and physical activity counseling resulted in statistically significant weight gain prevention as compared with control at 24 months (-2.1 kg difference).79 The other group in this study used phone-based diet and physical activity counseling which did not result in meaningful, statistically significant weight gain prevention at 24 months.79 Another study demonstrated no meaningful or statistically significant difference between intervention and control at 12 months.74 Finally, the military based study only provided results among subgroups,73 which are presented in the section below (Figure 7; Appendix E, Evidence Table 13).

Figure 7 describes the differences in weight change among adults in a work setting for combination interventions. Three studies are included in this figure, two with timepoints at 12 months, and one with additional timepoint at 24 months and one with final timepoint at 24 months.

Figure 7

Differences in weight change for combination interventions among adults in a work setting. Kg = kilogram; NR = not reported If the study did not report an estimate of variability, no confidence intervals were generated.

Waist Circumference Change

Two trials evaluated waist circumference as an outcome.74,79 Using our predefined criteria for waist circumference change of 1.0 cm over 12 months, one study met our between group difference threshold and was statistically significant.74 This intervention combined a self-management intervention with an environmental intervention. This study also resulted in statistically significant prevention of waist circumference increase at 24 months.74 The other study found no statistically significant differences between intervention and control groups with respect to prevention of waist circumference increase.79 (Figure 8, Appendix E, Evidence Table 13).

Figure 8. describes the differences in waist circumference change among adults in a work setting for combination interventions. Two studies are analyzed at 12 and 24 months.

Figure 8

Differences in waist circumference for combination interventions among adults in a work setting. cm = centimeter; NR = not reported; WC = waist circumference Size of the effect symbol reflects the sample size.

Adherence

Three trials reported an assessment of participation in or adherence to the intervention.76,77,79 One study created a participation score (with a range of zero to100, where higher scores indicate greater participation) that was based on survey responses to questions regarding awareness and use of the environmental interventions.76 The 12 month mean participation score was 15.8 and the 24 month mean participation score was 18.1 among intervention sites. The other two studies examined several process measures related to individual participation in the intervention79 and implementation of environment level changes.77 One of these studies compared participation in the intervention groups (telephone-based vs. Internet-based counseling). In this study, 64 percent of those randomized to telephone intervention completed all counseling modules versus 17 percent randomized to Internet intervention.79 The other study focused heavily on environment level changes.77 No worksites met the goal of reducing the price of healthy foods, while a majority of sites enhanced their stairwells and stocked their local food sources with healthier foods. (Appendix E, Evidence Table 13)

Clinical Outcomes

No studies reported on mortality or quality of life.

Adverse Events

No studies reported on adverse effects such as burden of intervention, nutritional deficiencies, eating disorders, or activity related injury.

Subgroups

The trial in the military setting reported the 12 month mean change in weight among subgroups of men and women.73 Women in the intervention group lost a mean of 0.1 kg, whereas women in the control group gained 0.4 kg. This 0.5 kg difference met our predefined criteria for weight maintenance and was statistically significant. (Appendix E, Evidence Table 9). The study in the chemical company setting performed a stratified analysis by gender, which did not reveal any significant interaction between the intervention and gender.80 No other subgroup analyses were performed in the other studies.

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

All work-based environmental level interventions were used in combination with other interventions, and are reported under Key Question 5.75-78,82

Weight Gain Prevention Among Adults in College-Based Settings

Study Characteristics

Two trials (155 participants) took place in a college setting.83,84 Both interventions were randomized trials at a single school. The duration of the interventions ranged from 16 to 24 months. The earliest year of recruitment was 199784 and the latest year of recruitment was 2002.83 One trial occurred in the United States84 (40 students randomized; 34 analyzed) and the other trial took place in Canada (115 students randomized; 105 analyzed).83

The stated study goal for both of the studies was the prevention of weight gain (Appendix E, Evidence Table 14).

Population Characteristics

The trials had similar populations.83,84 The mean age was 19 years and the majority of participants were White. Both studies included only freshman and sophomore college students. One study examined only women,84 while the other study included both women and men (Table 9; Appendix E, Evidence Table 15).83

Table 9. Description of interventions in studies among adult populations in college-based settings.

Table 9

Description of interventions in studies among adult populations in college-based settings.

Interventions

Both college based trials used a combined strategy to target weight maintenance in the intervention group including diet and exercise education. One study also included education on self management (Appendix E, Evidence Table 16).

Outcomes

Key Points

  • BMI
    • The strength of evidence is low that college based combination interventions that use self-management, dietary, and physical activity components prevent BMI gain. One college based intervention that combined self-management, diet, and physical activity components resulted in meaningful and statistically significant prevention of BMI change at 12 months. The other college based combination intervention demonstrated meaningful prevention of BMI gain; however, these results were not statistically significant.
    • There is insufficient evidence that self-management, diet, physical activity, medication, or environmental interventions alone in the college setting prevent BMI gain in adults.
  • Weight
    • The strength of evidence is low that college based combination interventions that use self-management, dietary, and physical activity components prevent weight gain. One college based intervention that combined self-management, diet, and physical activity components resulted in meaningful and statistically significant prevention of weight gain at 12 months. The other college based combination intervention demonstrated meaningful prevention of weight gain; however, these results were not statistically significant. In subgroups analysis, this intervention did show a meaningful and statistically significant effect among students whose baseline BMI greater than 24 kg/m2.
    • There is insufficient evidence that self-management, diet, physical activity, medication, or environmental interventions alone in the college setting prevent weight gain in adults.
  • Waist circumference
    • Neither intervention was favored to prevent waist circumference increases between a combination of self-management, dietary, and physical activity interventions and the comparison groups in the college setting (low strength of evidence).
    • There is insufficient evidence that self-management, diet, or physical activity interventions alone in the college setting prevent increase in waist circumference in adults.
  • Adherence
    • The strength of evidence for adherence is low. We identified only one study that assessed adherence among college based combination interventions. Adherence to the intervention was low during the first year, and declined further during the second year to less than 30 percent of participants.
  • Other outcomes
    • There is insufficient strength of evidence on the influence of college based combination interventions on other outcomes, because no studies met our inclusion criteria.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of self-management strategies and weight maintenance among adults in a college based setting met our inclusion criteria.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of dietary strategies and weight maintenance among adults in a college based setting met our inclusion criteria.

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of physical activity strategies and weight maintenance among adults in a college based setting met our inclusion criteria.

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No study on the use of orlistat and weight maintenance among adults in a college based setting met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of a combination of self-management, dietary, physical activity, and medication strategies for the prevention of weight gain among adults?

Both trials targeted freshman or sophomore students to provide them education on diet and exercise. One trial evaluated the effects of a 4 month college course on the science of nutrition, exercise, physiology, and metabolism on weight gain prevention.84 The course included both lectures and laboratory exercises on these topics. The other trial evaluated the effects of a 24 month weight gain prevention program using small groups to increase knowledge on diet and exercise, as well as self-management principles including problem solving, goal setting, and monitoring strategies.83 The control group participants for both of these trials received no information or intervention (Appendix E, Evidence Table 17).83,84

BMI Change

Both trials evaluated change in BMI.83,84 Using our predefined criteria for BMI change of 0.2 kg/m2 over 12 months, both studies met our between group difference threshold83,84. However, only one trial achieved a statistically significant effect on prevention of BMI gain83. This intervention used small group sessions to promote self-management, diet and physical activity in order to prevent weight gain. (Figure 9; Appendix E, Evidence Table 17).

Figure 9 describes the differences in BMI change among adults in a college setting for combination interventions. Two studies are included in this figure, one with timepoints at 12 and 24 months and one with timepoint at 16 months.

Figure 9

Differences in BMI change for combination interventions among adults in a college setting. BMI = body mass index; kg/m2 = kilogram/meter2 If the study did not report an estimate of variability, no confidence intervals were generated.

Weight Change

Both trials reported on weight change83,84. Using our predefined criteria for weight change of 0.5 kg over 12 months, both studies met our between group difference threshold 83,84. However, only one trial achieved a statistically significant effect on prevention of weight gain83. This intervention used small group sessions to promote self-management, diet and physical activity in order to prevent weight gain. The college course intervention had a between group difference of 3.2 kg at 16 months; however, this result was not statistically significant (Figure 10)84.

Figure 10 describes the differences in weight change among adults in a college setting for combination interventions. Three studies are included in this figure, two timepoints at 12 months, one with followup timepoint at 24 months and one with timepoint at 16months.

Figure 10

Differences in weight change for combination interventions among adults in a college setting. Kg = kilogram If the study did not report an estimate of variability, no confidence intervals were generated.

Waist Circumference Change

One trial reported on waist circumference.83 There was no difference in waist circumference change between the intervention and the control groups at 12 or 24 months (Appendix E, Evidence Table 17).

Adherence

Adherence to the intervention was reported in one trial.83 This study defined adherence as attending more than 60 percent of seminars during a 12 month period. During year 1, adherence was 53 percent and fell to 26 percent during year 2 (Appendix E, Evidence Table 17).

Clinical Outcomes

No studies reported on mortality or quality of life.

Adverse Events

No studies reported on adverse effects such as burden of intervention, nutritional deficiencies, eating disorders, or activity related injury.

Subgroups

One trial evaluated the effects of the intervention on subgroups based on BMI: BMI less than or equal to 24 kg/m2 and BMIs> 24 kg/m2) at baseline.84 There were no differences in 16 month BMI change between intervention and control participants who had lower BMIs at baseline. However, the higher BMI intervention group (n=11) lost 1.4 kg as compared with higher BMI controls (n=6) who gained 9.2 kg. This difference met the between group difference threshold and was statistically significant (Appendix E, Evidence Table 17).

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

No college based studies reported on environmental strategies.

Weight Gain Prevention Among Adults at Risk for or With Cardiovascular Disease or Diabetes Mellitus

Study Characteristics

Eleven randomized clinical trials85-98 and one non randomized clinical trial99 evaluated the effect of self-management, dietary, and/or physical activity interventions on weight maintenance among adults at risk for or with established cardiovascular disease or diabetes mellitus. One of the included trials, the Oslo Diet and Exercise Study (ODES), reported relevant results in two published articles,85,86 and another, The PREDIMED (Prevencion con Dieta Mediterranea) Study, reported relevant results in three published articles (Appendix E, Evidence Table 18).91,92,94

One trial was conducted in Australia,93 one in Asia,87, four in the United States,90,97-99 and five in Europe.85,86,88,89,91,92,96 Seven of the 12 trials did not report years of recruitment.88,89,93,95,97-99 Of those reporting on time of recruitment, three recruited between 2001 and 200787,94,96 and two recruited between 1990 and 1992.85,86 ,90 Three trials were conducted at more than one site,90-92 ,94,98 and with the exception of a single study that did not report on the number of sites,97 the others were conducted at a single study site.85-89,93,95,96,99 Seven trials recruited participants from a clinical setting.88,89,91-95,98,99 Other settings for recruitment included a cohort study,85,86 insurance plan,87 and diabetes screening program.96,97 Two trials did not report on the recruitment setting (Appendix E, Evidence Table 18).90,95

Six trials restricted inclusion exclusively to those with diabetes mellitus.88,89,93,97-99 Of these studies, one excluded patients not on insulin,99 and one excluded those without a stable diabetes medication regimen.89

Six trials were conducted in participants with risk factors for cardiovascular disease or diabetes mellitus such as dyslipidemia, elevated blood pressure, elevated BMI, or elevated hemoglobin A1c (HbA1c).85-87,90-92 ,94-96 Of these six trials, four excluded participants with known cardiovascular disease,85,86,90-92,94,95 and three excluded participants with diabetes.85,86,90,95 One trial required all participants to have impaired glucose tolerance (Appendix E, Evidence Table 18).96

Most articles did not report on total followup period;87-92,94-96 when reported, followup periods ranged from 1 to 2 years.85,86,93,97-99

Weight maintenance was a stated goal in a single article (Appendix E, Evidence Table 18).99

Population Characteristics

The 12 trials enrolled or randomized 4,206 participants.85-90,93-99 Two trials did not report the sex of the study population.85,86,99 Women comprised 31 to 100 percent of the study population in the other studies.87-99 Three trials did not report on the age of participants.85,86,90,99 In another trial, the reported mean age by sex was 57 years for women and 48 years for men.95 Mean age ranged from 57 to 68 yearsin the other trials.87-89,91-94,96-98 Only three trials reported on race and ethnicity; black participants comprised 17 percent of the study population in one trial,90 and 26 percent of participants in another trial were Asian or Pacific Islander (Appendix E, Evidence Table 19).96 All participants were Latina in a third trial.98

Education was reported qualitatively in a one trial in which roughly one half of participants were college graduates.90 In the PREDIMED Study, 73 to 76 percent of participants had less than a high school education in the control and two active diet intervention groups.94 In a trial conducted among Latinas with diabetes, less than one-third of participants reported post-secondary education,98 and another trial reported that 65 percent of participants had some post-secondary education.97 Smoking was reported in three trials with roughly 10 to 20 percent of participants reporting current smoking.85,96,98 One study excluded current smokers (Appendix E, Evidence Table 19).93

Roughly half of the participants in the PREDIMED Study had diabetes,94 and in another study, 14 to 20 percent of participants had diabetes.87. All participants were on insulin in one study of patients with diabetes (Appendix E, Evidence Table 19).99

Interventions

We did not identify any trials evaluating the effect of orlistat on weight maintenance among adults. Two trials compared a self-management intervention with a control group,88,98 two trials evaluated dietary interventions,91,92,94,99 two evaluated physical activity interventions,91,92,94,95,99 and six trials evaluated a combination of a self-management, dietary, or physical activity interventions (Tables 10-13; Appendix E, Evidence Table 20).87,89,90,93,95,97

Outcomes

Key Points

  • BMI. There is low strength of evidence that:
    • Goal setting to improve dietary and physical activity patterns results in a meaningful favorable BMI change at one year compared with no intervention.
    • Goal setting to improve physical activity decreases BMI meaningfully at one year.
    • Dietary interventions decrease BMI similarly compared with control at one year.
    • Physical activity interventions decrease BMI meaningfully at one year relative to no intervention.
    • A self-management intervention combined with physical activity results in a meaningful BMI change relative to control at one year.
    • A combination of self-management, physical activity, and diet results in a meaningful BMI change at one but not two years.
  • Weight. There is low strength of evidence that:
    • Dietary interventions do not prevent meaningful weight gain.
    • Physical activity interventions prevent meaningful weight gain compared with no intervention at one year.
    • A combination of physical activity and self management prevented weight gain meaningfully compared with usual care at one year.
    • A combination of diet, physical activity, and self management prevented weight gain meaningfully at one year compared with no intervention.
    • There is insufficient strength of evidence for self-management strategies, because no studies were identified.
  • Waist circumference. There is low strength of evidence that:
    • Goal setting to improve dietary and physical activity patterns meaningfully decreases waist circumference at one year compared with no intervention.
    • Endurance exercise decreases waist circumference meaningfully and statistically significantly compared with no intervention.
    • A combination of self management, aerobic activity and strength training resulted in meaningfully and statistically significantly less of an increase in waist circumference compared with control.
    • There is insufficient evidence on the effect of dietary interventions on waist circumference.
  • Adherence. There is low strength of evidence that:
    • Adherence to endurance exercise three times per week was 57 percent over one year.
    • Adherence to a combination of self-management and physical activity interventions ranged from 64 to 100 percent.
    • Adherence to a combination of self-management, dietary, and physical activity interventions was 46 percent.
    • There is insufficient strength of evidence for self-management and dietary strategies, because no studies met our inclusion criteria.
  • Quality of life
    • There is low strength of evidence that no strategy results in improved quality of life between an intervention that included a combination of self management and physical activity compared with control.
    • There is insufficient strength of evidence for self-management, dietary and physical activity interventions, because no studies met our inclusion criteria.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

Two randomized controlled trials (N=196 enrolled and analyzed) evaluated the effects of a self-management interventions on BMI and waist circumference maintenance among adults with diabetes.88,97 In one study, the self-management intervention focused on goal setting to improve dietary and physical activity patterns using motivational interviewing (Table 1); assessment of diet and physical activity was used to identify and address barriers to meeting lifestyle goals.88 Participants in this self-management intervention attended three in person sessions and had three telephone contacts.88 The comparison group received usual care.

In the other trial, the self-management interventions focused on physical activity goals using a teaching method grounded in Social-Cognitive Theory (Table 1).97 Participants in this study were randomized to either an intensive Diabetes Education Program (DEP) with 11 group, in-person contacts and telephone support over 12 months or to the DEP with Physical Activity Supplement (DEP + PAS) which offered an individualized exercise prescription and telephone support provided by a certified personal trainer in addition to the DEP (Table 1).97

Four other trials included self management as a component of the active intervention strategy and are described below in the section on studies evaluating a combination of intervention types (Table 10; Appendix E, Evidence Table 21).87,89,90,93

Table 10. Description of self-management interventions among adult patients with or at risk for cardiovascular disease and diabetes.

Table 10

Description of self-management interventions among adult patients with or at risk for cardiovascular disease and diabetes.

BMI Change

In the study comparing a self-management intervention with usual care, at 12 months, mean BMI had increased by 1.42 kg/m2 in the usual care group and remained stable (mean change from baseline, 0.34 kg/m2) in the self-management intervention group; while it met our predefined threshold for significance, the statistical significance of this 1.76 kg/m2 between-group change in BMI was not provided(Appendix E, Evidence Table 21).88 All randomized participants were presumed to be included in the analysis (N=100), but this was not reported.88 In the study comparing two self-management interventions, at 12 months, BMI decreased by 1.2 kg/m2 in the DEP group and by 0.8 kg/m2 in the DEP + PAS group (between group difference 0.4 kg/m2 (p<0.1 for adjusted between-group difference); this difference met our predefined threshold for significance, but its statistical significance was unclear.97 The authors carried the last observation forward for missing data in this study.97

Weight Change

There were no self-management interventions in this population that measured weight change as an outcome.

Waist Circumference Change

In the study comparing a self-management intervention with usual care, at 12 months, mean waist circumference had increased by 2.4 cm in the usual care group and decreased by 1.5 cm in the self-management intervention group.88 This difference in mean change in waist circumference from baseline between the groups did not reach statistical significance (3.9 cm,(Figure 11; Appendix E, Evidence Table 21).88 All randomized participants were presumed to be included in the analysis (N=100), but this was not reported.88 In the study comparing two self-management interventions, at 12 months, waist circumference decreased by 3.2 cm in the DEP group and by 5.2 cm in the DEP + PAS group (between group difference 2 cm (95% CI, -4.1 to 0.08; p>0.1 for adjusted between-group difference).97 The authors carried the last observation for missing data in this study.97 The between-group changes in waist circumference in both studies met our pre-defined threshold for significance but were not statistically significant.88,97

Figure 11 describes the difference in waist circumference change due to self management interventions among adults at risk for or with cardiovascular disease or diabetes mellitus for diet interventions. Two studies are analyzed at 12 months.

Figure 11

Differences in waist circumference change for self-management interventions among adults with diabetes mellitus. Size of the effect symbol reflects the sample size. Confidence interval provided only if available from the article.

Adherence

There were no self -management interventions in this population that measured adherence as an outcome.

Clinical Outcomes

The included studies did not report on mortality or quality of life.

Adverse Events

The included studies did not report on burden of the intervention, nutritional deficiencies, eating disorders, activity related injury, or other adverse events.

Subgroups

The included studies did not report results by baseline weight, gender, age, life events, race, ethnicity, cultural group, income, socioeconomic status, educational attainment, or family history of obesity.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

Two intervention studies (enrolled/randomized N=1806) evaluated the effects of a dietary intervention compared with another dietary intervention or to a control group on weight maintenance among adults at risk for or with established cardiovascular disease or diabetes.94,99 In a non randomized trial conducted at a single Veterans Administration (VA) outpatient diabetes clinic in the 1970s, patients with diabetes who were on insulin therapy were assigned to either 1) the American Diabetes Association (ADA) exchange diet which specified a daily caloric goal and carbohydrate distribution or 2) the standard “diabetic maintenance diet” which emphasized avoidance of simple sugars but set no specific daily caloric goal or pattern of carbohydrate intake.99

Patients in both groups received education about their assigned diet over 24 months during regularly scheduled quarterly clinic visits with a dietician.99 In The PREDIMED Study, participants with diabetes or at least three cardiovascular disease risk factors were randomized to 1) a Mediterranean diet with virgin olive oil, 2) a Mediterranean diet with mixed nuts, or 3) a control group in which they received printed materials and met with a dietician once for recommendations on following an American Heart Association diet.94

Participants randomized to the Mediterranean diet groups met individually once a quarter with study dieticians for motivational interviews and in group education sessions on the Mediterranean diet.94 Participants also received either free virgin olive oil or mixed nuts based on their study group.94

Three additional studies included a dietary component in their active intervention and are described below in the section on studies studying a combination of intervention types (Table 11).87,90,95

Table 11. Description of diet interventions among adult patients with or at risk for cardiovascular disease and diabetes.

Table 11

Description of diet interventions among adult patients with or at risk for cardiovascular disease and diabetes.

BMI Change

Similar proportions of participants the two dietary interventions and usual care groups (approximately 40 percent) experienced a decrease in BMI during the first 12 months of the PREDIMED Study (1,551 analyzed of 1,776 randomized participants; Appendix E, Evidence Table 21) (p=0.464).94

Weight Change

In the VA based study (enrolled and analyzed N=30), weight increased with both diets but less so in the ADA diet group at 12 months.99 The mean between group difference in weight for the ADA versus standard diet group was 0.8 kg at 12 months and met our predefined threshold for significance but was not statistically significant.99) By 24 months both groups had gained nearly 1 kg (Figure 12).99 In a sub analysis of 737 participants from the PREDIMED Study, compared with the control group, participants in the olive oil based group lost an average of 0.1 (95% CI, 0.1 to 0.2), p<0.0001 for weight loss) kg and the nut based group had gained 0.03 kg at 36 months (Figure 12).92 The average weight loss at 36 months was 0.1 kg less in the nut based compared with olive oil based intervention group (Appendix E, Evidence Table 21).92 The between-group differences in weight change in PREDIMED did not meet our predefined threshold for significance nor were they statistically significant.92

Figure 12 describes the differences in weight change among adults at risk for or with cardiovascular disease or diabetes mellitus for diet interventions. Two studies are included in this figure, one with timepoints at 12 and 24 months, and another with timepoint at 36 months.

Figure 12

Differences in weight change for diet interventions among adults at risk for or with cardiovascular disease or diabetes mellitus. ADA = American Diabetic Association; kg = kilogram Dotted line indicates a meaningful between group change of 2.5kg.

Waist Circumference Change

In another PREDIMED Study sub analysis, which included a random sample of participants completing the study (N=187), baseline waist circumference was significantly higher in the olive oil based Mediterranean diet group compared with the control group (98.8 cm vs. 93.8 cm, p=0.005); baseline waist circumference was 96.7 cm in the nut based Mediterranean diet group.91 Waist circumference increased by 0.1 cm in the control group and decreased by 0.6 in the olive oil based and 0.2 cm in the nut based groups by 36 months (Figure 13).91 Compared with the control group, participants in the olive oil based group and the nut based group experienced an average decrease in waist circumference of 0.7 (95% CI, 2.4 to 0.9 cm, p=0.38) and 0.3 (95% CI, 1.8 to 1.1 cm, p=0.65) cm at 36 months, and the average decrease in waist circumference was 0.4 (95% CI, 1.1 to 1.9 cm, p=0.59) cm less in the nut based compared with olive oil based intervention group (Appendix E, Evidence Table 21).91 The between-group differences in weight change in this study did not meet our predefined threshold for significance nor were they statistically significant.91

Figure 13 describes the differences in waist circumference change among adults at risk for or with cardiovascular disease or diabetes mellitus for diet interventions. One study is included in this figure with final timepoint at 36 months.

Figure 13

Differences in waist circumference change for diet interventions among adults at risk for or with cardiovascular disease or diabetes mellitus. Cm = centimeter; WC = waist circumference Dotted line indicates a meaningful between-group change of 2 cm.

Adherence

There were no dietary interventions in this population that measured adherence as an outcome.

Clinical Outcomes

The included studies did not report on mortality or quality of life.

Adverse Events

The included studies did not report on burden of the interventions, nutritional deficiencies, eating disorders, activity related injury, or other adverse events.

Subgroups

The included studies did not report results by baseline weight, gender, age, life events, race, ethnicity, cultural group, income, socioeconomic status, educational attainment, or family history of obesity.

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

Two trials evaluated the effect of a physical activity intervention relative to a control intervention on weight maintenance among adults at risk for cardiovascular disease or diabetes.85,86 ,96 These trials randomized 195 participants, and provided results for 166 participants.85,86,96 In the Pre diabetes Risk Education and Physical Activity Recommendation (PREPARE) trial, participants in the active interventions attended a 180 minute group informational session about exercise, which addressed barriers to walking at baseline. Participants were subsequently followed up for 10 minute visits at 3 and 6 months to review their progress.96 In one of the two active intervention groups, participants also received a pedometer to help them meet the recommended number of steps per day.96 In the Oslo Diet and Exercise Study (ODES), participants in the active intervention group attended supervised endurance exercise sessions three times per week.85

Four additional trials included a physical activity component in their active interventions and are discussed below in the section on studies evaluating a combination of intervention types (Table 12).87,89,93,95

Table 12. Description of physical activity interventions among adult patients at risk for cardiovascular disease and diabetes.

Table 12

Description of physical activity interventions among adult patients at risk for cardiovascular disease and diabetes.

BMI Change

Studies provided results on 166 of 195 randomized participants for analyses of BMI change.86,96 In the ODES, the physical activity intervention resulted in a slight decrease in BMI, whereas the usual care group experienced a slight increase in BMI.86 The mean between group difference in BMI at 12 months with usual care group as reference was 0.7 (95% CI 0.8 to 0.6, p<0.001) kg/m2 and thus met our predefined threshold for significance in addition to being statistically significant (Figure 14).86 Compared with usual care, between group differences (95% CI) in BMI for the PREPARE and PREPARE and pedometer active interventions were 0.2 ( 0.5 to 0.9, p=0.575) kg/m2 and 0.5 kg/m2 ( 0.3 to 1.2, p=0.212) at 12 months (Figure 14; Appendix E, Evidence Table 21); these between-group differences met our predefined threshold for significance but were not statistically significant 96

Figure 14 describes the differences in BMI change among adults at risk for or with cardiovascular disease or diabetes mellitus for physical activity interventions. Two studies are included in this figure, both with final timepoints at 12 months.

Figure 14

Differences in BMI change for physical activity interventions among adults at risk for or with cardiovascular disease or diabetes mellitus. BMI = body mass index; kg/m2 = kilogram/meter2 If the study did not report an estimate of variability, no confidence (more...)

Weight Change

Studies provided results on 166 of 195 randomized participants for analyses of weight change.86,96 In the ODES, weight increased by 1.1 kg in the usual care group and decreased by 0.9 kg in the physical activity intervention group. The between group mean difference in weight was 2.0 kg (95% CI, 3.4 to −0.6, p=0.007) over 12 months for the active group compared with the control and thus both met our predefined threshold for significance and was statistically significant (Figure 15).85 Compared with usual care, between group differences in weight for the PREPARE and PREPARE plus pedometer active interventions were 0.3 (95% CI, 1.8 to 2.5, p=0.749) kg and 1.4 (95% CI 0.8 to 3.5, p=0.199) kg at 12 months with the comparison including PREPARE plus pedometer meeting our predefined threshold for significance (Figure 15; Appendix E, Evidence Table 21).96 The between-group differences in weight change in PREPARE were not statistically significant.96

Figure 15 describes the differences in weight change among adults at risk for or with cardiovascular disease or diabetes mellitus for physical activity interventions. Two studies are included in this figure, both with final timepoints at 12 months.

Figure 15

Differences in weight change for physical activity interventions among adults at risk for or with cardiovascular disease or diabetes mellitus. kg = kilogram Dotted line indicates a meaningful between group change of 2.5kg.

Waist Circumference Change

In the ODES, waist circumference increased by 0.9 cm in the usual care group and decreased by 1.9 cm in physical activity intervention group. The between group mean difference in waist circumference at 12 months was 2.8 (95% CI 4.3 to 1.3, p=0.0003) cm for the active compared with the control group (Appendix E, Evidence Table 21) and thus met our predefined threshold for significance and was statistically significant..85 Results on waist circumference were provided for 92 of 97 randomized participants.85

Adherence

Exercise adherence (attendance at exercise sessions) was 57 percent in the physical activity intervention group of the ODES (Appendix E, Evidence Table 21).85 Results on adherence were provided for 49 of 54 participants randomized to the active exercise intervention group of the ODES.85

Clinical Outcomes

The included studies did not report on mortality or quality of life.

Adverse Events

The included studies did not report on burden of the interventions, nutritional deficiencies, eating disorders, activity related injury, or other adverse events.Subgroups

The included studies did not report results by baseline weight, gender, age, life events, race, ethnicity, cultural group, income, socioeconomic status, educational attainment, or family history of obesity.

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No study on the use of orlistat and weight maintenance among adults in a at risk for cardiovascular disease or type 2 diabetes mellitus met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of a combination of self-management, dietary, physical activity, and medication strategies for the prevention of weight gain among adults?

Six trials (N=1984 randomized) evaluated the effect of a combination of a self-management, dietary, or physical activity interventions on weight maintenance among adults with or at risk for cardiovascular disease or diabetes.87,89,90,93,95,98 Two trials evaluated the effect of a self-management intervention combined with physical activity in patients with diabetes, and both trials emphasized increasing physical activity and goal setting .89,93 The trials of Hypertension Prevention Phase II (TOHP II) evaluated the effect of a sodium reduction strategy employing dietary and self management in overweight people with suboptimal blood pressure (Table 4).90 The Diet and Exercise for Elevated Risk (DEER) trial compared the effects of a dietary intervention, physical activity intervention, and a combination diet and physical activity intervention in men and women with elevated LDL and low HDL,95 This trial provided results stratified by sex.95 Two trials compared the effect of the combination of a dietary, physical activity, and a self-management intervention compared with a control intervention in people with diabetes or elevated blood pressure or elevated HbA1c (Table 13).87,98 One of these trials limited enrollment to Latina women with type 2 diabetes and evaluated an intensive, culturally-adapted combination intervention relative to enhanced usual care (Table 13).98

Table 13. Description of combination interventions among adult patients at risk for cardiovascular disease and diabetes.

Table 13

Description of combination interventions among adult patients at risk for cardiovascular disease and diabetes.

BMI Change

Studies provided results on 384 of 473 randomized participants for analyses of BMI change at 12 months.87,89,93,98 Relative to control, the combination of physical activity with self-management strategies in two studies resulted in decreases in BMI ranging from 0.4 to 0.7 kg/m2 at 12 months (Figure 16).89,93 While these between-group changes met our predefined threshold for significance, they were not statistically significant. For the intervention that emphasized both aerobic activity and strength training, compared with the control, the between group difference in BMI was neared statistical significance: 0.7 ( 1.4 to 0.0, p=0.049) kg/m2.89

Figure 16 describes the differences in BMI change among adults at risk for or with cardiovascular disease or diabetes mellitus for combination interventions. Three studies are included in this figure, all with final timepoints at 12 months.

Figure 16

Differences in BMI change for combination interventions among adults at risk for or with cardiovascular disease or diabetes mellitus. Size of the effect symbol reflects the sample size. Confidence interval provided only if available from the article. (more...)

In the trials comparing the combination of self management, physical activity, and diet with control, at 12 months, both control groups experienced a small decrease in BMI, and both active intervention group's experienced larger decreases in BMI.87,98 Compared with the control group, BMI decreased 0.4 kg/m2 more in the active intervention group in one study (statistical significance of the between group change not reported) 87 and 0.7 kg/m2 more in the active intervention group of the other study98; (Figure 15; Appendix E, Evidence Table 21) and thus met our predefined threshold for significance. By 24 months (N=190 for analysis), BMI decreases from baseline were similar for the intervention and control groups (between-group difference in BMI, -0.1 kg/m2 for the active intervention vs. control; p<0.05 for effect of intervention over time including all follow up time points (6, 12, and 24 months)); this between-group change at 24 months did not meet our predefined threshold for significance.98

Weight Change

Studies provided results on 1,337 of 1,352 randomized participants for analyses of weight change.87,89,90,93 Relative to the control, the combination of physical activity with self-management strategies resulted in decreases in weight ranging from 0.7 to 1.3 kg at 12 months which met our predefined threshold for significance but were not statistically significant (Figure 17).89,93 In the randomized trial comparing the combination of self management, physical activity, and diet with control, both groups experienced a small decrease in weight at 12 months, but this decrease was 0.9 kg more in the active intervention group and thus met our predefined threshold for significance (statistical significance of the between group change not reported (Figure 17).87 Mean weight increased slightly in the control and sodium reduction group of TOHP II at 36 months, but this difference was not significant statistically or by our predefined threshold for significance. The between group difference in weight was 0.1 kg (95% CI 0.7 to 0.5), p=0.75 (Figure 17; Appendix E, Evidence Table 21).90

Figure 17 describes the differences in weight change among adults at risk for or with cardiovascular disease or diabetes mellitus for combination interventions. Three studies are included in this figure, two with final timepoints at 12 months, and one with final timepoint at 36 months.

Figure 17

Differences in weight change for combination interventions among adults at risk for or with cardiovascular disease or diabetes mellitus. Kg = kilogram; Na+ = sodium; NR = not reported Dotted line indicates a meaningful between group change of 2.5kg.

Waist Circumference Change

Relative to the control, the combination of physical activity with self-management strategies resulted in a decrease in waist circumference at 12 months in one trial.89 In the intervention that emphasized both aerobic activity and strength training, compared with the control the between group difference in waist circumference was statistically significant and met our predefined threshold for significance: 2.4 (95% CI, 4.7 to 0.0 cm, p=0.047) (Appendix E, Evidence Table 17).89 This study provided results on 65 of 68 randomized participants.89

Adherence

Two trials combining self-management and physical activity interventions reported on adherence.89,93 Attendance at intervention sessions was 63.5 percent and 64.6 percent in the active intervention groups for one trial89 and 100 percent in the other trial (Appendix E, Evidence Table 17).93 Studies provided results on 58 of 59 randomized to an active intervention for analyses of adherence.89,93 Mean attendance at sessions for a study incorporating self-management, diet, and physical activity interventions was 46 percent between 12 and 24 months of follow up; this study provided information on 97 of 142 randomized participants.98

Quality of Life

The authors reported no significant differences in SF 36 results between groups in one study (Appendix E, Evidence Table 21).89 This study provided results on 65 of 68 randomized participants for this analysis.89

Other Clinical Outcomes

The included studies did not report on mortality.

Adverse Events

The included studies did not report on burden of the interventions, nutritional deficiencies, eating disorders, activity related injury, or other adverse events.

Subgroups

In the DEER Trial, both men and women experienced small increases in weight in the control group and decreases in weight in the three active intervention group's (exercise alone, diet alone, or diet and exercise); these changes in weight by treatment group met our predefined threshold for significance and were also statistically significant (p<0.001.95 Both the diet intervention and the combination of diet and exercise intervention modestly decreased weight relative to the control and exercise alone groups for both men and women.95 In the TOHPII, race and sex stratified analyses showed that changes in weight were smaller in the sodium reduction group for men and larger for women, but these weight change differences were not statistically significant; numeric results were not provided (Appendix E, Evidence Table 21).90 One trial of a self-management plus diet and physical activity intervention restricted enrollment to Latina women with type 2 diabetes; results are reported above.98

The included studies did not report results by baseline weight, age, life events, income, socioeconomic status, educational attainment, or family history of obesity.

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of environment level strategies and weight maintenance among adults among adults in a at risk for cardiovascular disease or type 2 diabetes mellitus met our inclusion criteria.

Weight Gain Prevention Among Adults With Cancer

Study Characteristics

Data on prevention of weight gain among adults with cancer were reported in three trials (reported in 4 articles) (baseline n=2,671; 2,362 analyzed)100-103 and one observational study (baseline n=1,966; 1,657 analyzed) (Appendix E, Evidence Table 22).104

Interventional Studies

All three of the interventional studies were randomized trials.100-103 One trial was reported in two publications.102,103 The duration of the interventions was 12 months in two studies100,103 and 36 months in another.101 One trial followed participants for an additional 24 months after the 36 month intervention.101 Two trials were conducted at multiple sites,100,101 one at a single site,100,103 and all were in the United States.100,101,103 Participants were recruited from clinical settings in two trials,100,101 and from the community in one trial.103 The first years of recruitment were 1994,101 1999,103 and unreported.100 One trial stated the specific goal of preventing weight gain (Appendix E, Evidence Table 22).100

Observational Study

One observational study was included.104 Patients were recruited at five months after cancer diagnosis and followed through 36 months after diagnosis (31 months of total followup).104 The study was a subanalysis of an Australian study to identify predictors of colorectal cancer before and after a screening program. Participants with histologically confirmed colorectal cancer that was reported to a citywide cancer registry during 2003 and 2004 were recruited (Appendix E, Evidence Table 22).104

Population Characteristics

Interventional Studies

Inclusion criteria based on age, timing of cancer diagnosis, and previous treatment for cancer were common. One trial included women with a first degree relative with breast cancer.102,103 The other trials recruited women with newly diagnosed cancer.100,101 One trial recruited women within 365 days of surgery for breast cancer.101 The other trial included women who had not yet received chemotherapy or radiation treatment for breast cancer, colon cancer, or lymphoma and whose treatment plan would include chemotherapy and a steroid.100 One trial included all adult women,100 another women aged 48 through 79 years,101 and another included only premenopausal, healthy women between 21 and 50 years of age.102,103 Two trials had ethnically diverse populations,101-103 and one trial reported that 90% of participants were white without referencing the background population racial diversity.100 White participants accounted for 75 and 90 percent of the participants in the trials.101-103 The percentage of participants with a college degree or at least some college ranged from 49 to 80 percent and was reported in all trials (Appendix E, Evidence Table 23).

No trial restricted inclusion of participants based on weight or BMI. One trial required that participants were consuming at least 20 percent of their calories from fat,101 one required that fat intake was greater than 25 percent of calories and that fruit and vegetable intake was less than or equal to 5 servings per day,103 and one required baseline exercise of under 120 minutes per week.100 One trial reported smoking status; 50 percent of women were never smokers (Appendix E, Evidence Table 23).101

Observational Study

The observational study had very few exclusion criteria.104 All English speaking individuals who could respond to a phone interview aged 20 to 80 years old at the time of cancer diagnosis were included. Underweight women were excluded. Sixty one percent of participants were male. Seventy two percent of participants were 60 years or older. Forty six percent had a technical college or university degree. Forty percent were never smokers and seven percent were current smokers at five months after cancer diagnosis.104

At baseline, five months after cancer diagnosis, 45 percent of participants were a healthy weight, 37 percent were overweight and 18 percent were obese (Appendix E, Evidence Table 23).

Interventions

Two trials focused on dietary changes (one including a self-management strategy) and the other trial focused on physical activity. The goal of one trial was to reduce percentage calories from fat to 15 percent while otherwise maintaining a nutritionally adequate diet and maintaining baseline weight.101 Participants were randomized to receive counseling with a dietician every three months with specific emphasis on fat reduction (intervention group) or a goal of achieving adequate vitamin and mineral intake (comparison group) trials (Appendix E, Evidence Table 21).101 The intervention group's contact with dieticians focused on self-management strategies to achieve their fat reduction goals as well as group counseling sessions, quarterly mailing and more frequent assessments of weight and dietary adherence. 101

Another trial randomized participants to one of four diet groups: control (asked to follow their usual diet), low fat diet (<15 percent of calories from fat), high fruits and vegetables diet (9 servings/day), or a combination of low fat and high fruits and vegetables diet.103

Another trial randomized women to home based endurance exercise, resistance exercise or no exercise recommendation (Appendix E, Evidence Table 24).100

Approach

One observational study measured television viewing among individuals with primary colorectal cancer.104 Participants were asked how often they spent watching television during the previous month (Table 14).

Table 14. Description of self-management approach among adults with cancer.

Table 14

Description of self-management approach among adults with cancer.

Outcomes

Key Points

  • BMI. There is low strength of evidence that:
    • Television viewing results in meaningfully and statistically less BMI gain three years after cancer diagnosis among individuals with colorectal cancer.
    • Dietary interventions aimed at decreasing the percentage of calories from fat decrease BMI for up to 5 years, but are not statistically significant.
    • A dietary intervention aimed at decreasing the percentage of calories from fat combined with self-management counseling on monitoring fat intake, goal setting, social support and relapse prevention and management among women with newly diagnosed cancer decreased BMI at 1 year compared with women who received counseling on maintaining nutritional adequacy that did not include the self-management components. The BMI change met the meaningful between group threshold but statistical significance was not calculable.
    There is insufficient strength of evidence for physical activity interventions because no studies met our inclusion criteria.
  • Weight. There is moderate strength of evidence that:
    • Home based aerobic and resistance exercise prevents weight gain. Women with cancer who participated in home based aerobic or resistance exercise lost weight over one year compared with controls that gained weight. The findings were statistically significant and met the meaningful between group threshold.
    There is low strength of evidence that:
    • A low fat diet meaningfully reduces weight gain at 1 year compared with a dietary brochure, a high fruits and vegetables diet and a combination of a low-fat and high fruits and vegetables diet among premenopausal women with a family history of breast cancer. The statistical significance is unknown.
    • A dietary intervention aimed at decreasing the percentage of calories from fat combined with self-management counseling on monitoring fat intake, goal setting, social support and relapse prevention and management among women with newly diagnosed cancer decreased weight at 1 year compared with women who received counseling on maintaining nutritional adequacy that did not include the self-management components. The weight change met the meaningful between group threshold but statistical significance was not calculable.
  • Adherence. There is low strength of evidence that:
    • Adherence to low fat diets, high fruits and vegetable diets and exercise is possible in women with cancer. Continued adherence to a high fruits and vegetables diet is greater than to a low fat diet.
    • Adherence to aerobic and resistance exercise is possible for up to 1 year among women with cancer.
    There is low strength of evidence that adherence to the combination of a diet and self-management intervention is possible for 5 years, including 2 years after the cessation of the intervention. The fat consumption of the diet combined with self-management group was less than the consumption among those who received counseling related to maintaining nutritional adequacy and this difference was maintained for 5 years.
  • Adverse effects
    • There is low strength of evidence that the combination of a diet and self-management intervention had no adverse effects.
    • There is insufficient strength of evidence for adverse effects for self-management, dietary and physical activity interventions, because no studies met our inclusion criteria.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

One observational study measured television viewing among individuals with primary colorectal cancer five months after cancer diagnosis.104 Participants were asked how often they spent watching television during the previous month (Table 14).

BMI Change

The study enrolled 1,966 people at baseline (5 months after diagnosis) with information available for 1,657 people at 12 months, 1,202 people at 24 months and 1,028 at 36 months.104 BMI change from baseline was 0.7 kg/m2 (95% CI, 0.3 to 1.1) greater at 24 months among individuals reporting five or more hours of television per day compared with less than three hours per day of baseline television viewing after adjustment for baseline BMI, sex, age, education, smoking, cancer stage, mode of treatment, co morbidities and physical activity level. At 36 months, those individuals with more than five hours per day had an adjusted BMI change from baseline 0.6 kg/m2 greater (95% CI, 0.1 to 1.1) than the less than 3 hours of television per day group. These findings were statistically significant (p<0.001 at 24 months and p=0.01 at 36 months) and represent a meaningful between group difference (Appendix E, Evidence Table 25).

Weight Change

No study on self management and weight change met our inclusion criteria.

Waist Circumference Change

No study on self management and waist circumference change met our inclusion criteria.

Adherence

No study on self management and adherence met our inclusion criteria.

Clinical Outcomes

No study on self management and mortality, cancer, or quality of life met our inclusion criteria.

Adverse Events

No study on self management and burden of intervention, nutritional deficiencies, eating disorder, activity related injury, adverse effect of medication, or other adverse events met our inclusion criteria.

Subgroups

Those with no baseline physical activity (0 minutes per week) and 5 hours or more of television at baseline had the greatest increases in BMI at 24 (p for interaction=0.09) and 36 months (p for interaction not reported). The gender by baseline television interaction was not statistically significant at 24 months (p=0.95) or at 36 months (p=0.13). The effect estimates associated with the gender interaction models were not reported. No study on self management and results by baseline weight, age, life events, race, ethnicity, or cultural group met our inclusion criteria.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

One trial randomized premenopausal women with a family history of breast cancer to one of four diet groups for one year: brochure (asked to follow their usual diet and given brochures from the Daily Food Guide Pyramid and the National Dairy Council), low fat diet (<15 percent of calories from fat), high fruits and vegetables diet (9 servings/day), or a combination of low fat and high fruits and vegetables diet (Table 15).102,103

Table 15. Description of dietary intervention among adults with cancer.

Table 15

Description of dietary intervention among adults with cancer.

BMI Change

No study on dietary strategies and BMI change met our inclusion criteria.

Weight Change

Baseline and 12 month weights were reported for women who completed the full 12 month intervention. Over the 12-month intervention period, the brochure group lost 0.4 kg, the low-fat diet group lost 5.0 kg, the high fruits and vegeatbles group gained 1.8 kg and the combination group had no change in weight. Compared with the brochure group, the low-fat and combination groups had meaningful changes in weight over the intervention period. Weight change from baseline decreased with the the low-fat diet (-4.6 kg) and increased with the high fruits and vegeatbles diet (2.2 kg) compared with the change from baseline in the brochure group. Weight change from baseline also met the between group difference with a preference for the low-fat diet over the high fruits and vegeatbles diet (-6.8 kg difference) and combination diet (-5.0 kg). The study did not provide enough information to calculate statistical significance for any between group difference comparison. (Figure 18; Appendix E, Evidence Table 25).

Figure 18 describes the differences in weight change among adults with cancer for all interventions. Three studies are included in this figure, all with final timepoints at 12 months.

Figure 18

Differences in weight change from baseline to 1 year measured in kilograms among women with cancer. Kg = kilogram; PA = physical activity; SM = self-management Combo Diet = low fat + high fruits & vegetables.

Waist Circumference Change

No study on dietary strategies and waist circumference change met our inclusion criteria.

Adherence

Adherence to the fruits and vegeatbles, dietary fat consumption and study participation were reported. All groups, including the brochure group, increased their fruit and vegetable intake at one year.103 The groups assigned to increase fruit and vegetable consumption had the greatest increases in consumption of seven additional servings per day compared with less than 1 additional serving in the brochure and low fat groups. The decrease in calories from fat was 16 percent in the low fat group, two percent in the high fruits and vegetables group and 15 percent in the combination group. The percentage of calories from fat increased in the control group by one percent. Forty percent of women in the low fat group and 20 percent of women in the combination group dropped out of the study. Retention through the end of the one year intervention period was greater than 90 percent in the high fruits and vegetables and control groups (Appendix E, Evidence Table 25).103

Clinical Outcomes

No study on dietary strategies and mortality, cancer, or quality of life met our inclusion criteria.

Adverse Events

No study on diet and burden of intervention, nutritional deficiencies, eating disorder, activity related injury, adverse effect of medication, or other adverse event met our inclusion criteria.

Subgroups

No study on dietary interventions by baseline weight, gender, age, life events, race, ethnicity, or cultural group met our inclusion criteria.

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

One trial compared the effect of a home based exercise intervention on weight gain, body fat, and aerobic capacity.100 The study included women with a diagnosis of breast cancer, lymphoma, or colon cancer who exercised fewer than 120 minutes per week and who were chemotherapy naïve, but were planning to begin chemotherapy including a steroid as a part of the treatment. Participants were randomized to aerobic exercise, resistance exercise, or usual care control (Table 16). Only participants who completed the study (101 of 112 randomized) were reported on.

Table 16. Description of physical activity intervention among adults with cancer.

Table 16

Description of physical activity intervention among adults with cancer.

BMI Change

No study on physical activity strategies and BMI change met our inclusion criteria.

Weight Change

The control group gained 5.9 kg during the one year intervention period, whereas women in both exercise groups lost weight.100 The prevention of weight gain in the exercise groups met the meaningful threshold for change in weight from baseline compared with the control group. The finding was stated as statistically significant but the weight gain in the text does not match the numbers in the table reported in the following sentences (3.1 kg difference in mean weight change reported in text for the comparison of control to the combined value of the exercise groups). The aerobic exercise group gained 8.4 kg less than the control group. The difference in weight gain was 6.3 kg less for the resistance exercise group (Appendix E, Evidence Table 25).

Waist Circumference Change

No study on physical activity strategies and waist circumference change met our inclusion criteria.

Adherence

The trial reported on adherence to the intervention overall.100 Seventy nine percent of women assigned to the aerobic exercise group adhered to the assigned level of intervention, compared with 65 percent of resistance exercise participants at one year. All of the control group participants maintained inactive (Appendix E, Evidence Table 25). Many of the resistance exercise participants added a self-initiated aerobic exercise program. No mention is made of aerobic exercise participants adding a resistance exercise program.

Clinical Outcomes

No study on physical activity strategies and mortality, cancer, or quality of life met our inclusion criteria.

Adverse Events

No study on physical activity strategies and burden of intervention, nutritional deficiencies, eating disorder, activity related injury, adverse effect of medication, or other adverse event met our inclusion criteria.

Subgroups

No study on physical activity strategies by baseline weight, gender, age, life events, race, ethnicity, or cultural group met our inclusion criteria.

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No studies on the impact of orlistat on weight maintenance in populations with cancer met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of a combination of self-management, dietary, physical activity, and medication strategies for the prevention of weight gain among adults?

One trial (2,437 baseline; 2,164 analyzed) compared a combination of self-management and a low fat diet (15 percent reduction in fat) with no change in fat consumption.101 All participants received dietary counseling. The dietary counseling included individual sessions for both groups and optional group counseling for the low fat diet group. The low fat diet group's counseling included information on monitoring fat intake, goal setting, social support and relapse prevention and management to reduce dietary fat to 15 percent of caloric consumption (Table 17).

Table 17. Description of combination intervention among adults with cancer.

Table 17

Description of combination intervention among adults with cancer.

BMI Change

BMI decreased in the low-fat diet group (-0.8 kg/m2) and did not change in the comparison group (0.1 kg/m2) at 1 year. BMI change from baseline between groups met the threshold for clinical and statistical significance at 1 year. BMI change from baseline was 0.9 units lower in the low-fat diet group with self-management counseling compared with the group without a dietary change goal and no self-management counseling at 1 year, which met the threshold for a meaningful difference (insufficient information to calculate the statistical significance; Appendix E, Evidence Table 25).101 Although the intervention continued for 3 years and participants were followed for 5 years after randomization, the between group difference in the change from baseline could not be calculated after 1 year.

Weight Change

The low-fat diet group lost weight at 1 year (-2.1 kg) compared with a 0.2 kg increase in weight among the comparison group. The difference in weight from baseline to year 1 between groups met the meaningful difference threshold (-2.3 kg), but insufficient information was reported to assess the statistical difference (Appendix E, Evidence Table 25).101 Insufficient information was reported after 1 year to identify the difference in weight change from baseline between groups.

Waist Circumference Change

No study on combination strategies and waist circumference change met our inclusion criteria.

Adherence

The study reported that 80 percent of participants provided dietary data for at least three time periods after the baseline assessment. At year five, 40 percent of the intervention group and 68 percent of the control group reported dietary intake. Among the subset that reported dietary intake at year five, the total fat (in grams), percentage of calories from fat, saturated fat, polyunsaturated fat, monounsaturated fat, and total energy (in kilocalories) were lower in the low-fat diet group than the comparison group (p<0.0001 for all) and the fiber intake (in grams per day) was increased (p<0.01; Appendix E, Evidence Table 25).101

Cancer Recurrence

The low-fat diet combined with self-management intervention group was less like to experience cancer recurrence and had greater cancer-free survival compared with the comparison group (Appendix E, Evidence Table 25).101 There was a modest increase in overall survival (HR 0.89; 95% CI 0.65 – 1.21), but the finding was not statistically significant.

Adverse Events

The study specifically stated that no adverse events were associated with the low-fat dietary intervention but did not specify which adverse events were of interest or how adverse events were collected. It is unclear if adverse events were collected among the group without the low-fat diet goal (Appendix E, Evidence Table 25).101

Subgroups

The study reported that there was no interaction of the intervention by baseline BMI in an adjusted Cox regression model of cancer recurrence (p for interaction not reported). No study on combination strategies by baseline weight, gender, age, life events, race, ethnicity, or cultural group met our inclusion criteria.

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of environment level strategies and weight maintenance among adults with cancer met our inclusion criteria.

Weight Gain Prevention Among Adults With Mental Illness

Study Characteristics

Data on prevention of weight gain among adults with mental illness were reported in two trials (163 randomized; 150 analyzed).105,106 The interventions occurred for 3 months106 and 6 months.105 The studies assessed patients 18 months105 and 21 months106 after the intervention ended (Appendix E. Evidence Table 26). A specific weight maintenance goal was reported in one trial.106 One trial occurred at multiple group homes in Scotland.105 The Spanish trial was clinic based and did not report the number of clinics involved.106 The starting year of enrollment was 2002 in the one study that reported enrollment period (Appendix E. Evidence Table 26).106

Population Characteristics

The Spanish study aimed to prevent weight gain among individuals taking medications for their first treated episode of psychosis.106 The Scottish study provided fruits and vegetables to group homes with schizophrenic residents.105 The majority of patients were men (71 to 75 percent) and under 50 years old (mean age 27 and 45 years). Neither study made restrictions on weight for eligibility (Appendix E. Evidence Table 27).

Interventions

The Scottish study provided fruits and vegetables (5 servings per household member per day), fruits and vegetables plus lessons on preparing food, or no intervention to group homes.105 The Spanish study provided individual sessions on behavior management and education on diet and exercise (Appendix E. Evidence Table 28).

Outcomes

Key Points

  • There is low strength of evidence that:
    • Providing fruits and vegetables to households of people with schizophrenia does not prevent weight gain.
    • A behavioral intervention combined with education on diet and exercise prevents anti-psychotic medication associated weight gain through 2 years of followup, although the finding was not statistically significant. The intervention group gained 1.5 kg less (0.5 units of BMI) compared with the usual care group.
    There is insufficient strength of evidence for all other strategies and outcomes because no studies met our inclusion criteria.

Key Question 1. What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of self management and weight maintenance among adults with mental illness met our inclusion criteria.

Key Question 2. What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?

An trial of individuals with schizophrenia examined the impact of provision of free fruits and vegetables with and without instruction in meal planning and food preparation compared with no intervention on eating habits.105

BMI Change

The trial (102 randomized; 91 analyzed) stated that there were no significant differences in BMI between groups at 18 months from the start of the intervention. Quantitative results were not provided (Appendix E, Evidence Table 29).105

Weight Change

No study on dietary strategies and on weight change met our inclusion criteria.

Waist Circumference Change

No study on dietary strategies and waist circumference change met our inclusion criteria.

Clinical Outcomes

No study on dietary strategies and mortality or QOL met our inclusion criteria.

Adherence

No study on dietary strategies and adherence in populations with mental illness met our inclusion criteria.

Adverse Events

No study on diet and burden of intervention, nutritional deficiencies, eating disorder, activity related injury, adverse effect of medication, or other adverse events met our inclusion criteria.

Subgroups

No study on dietary strategies by baseline weight, gender, age, life events, race, ethnicity, cultural group met our inclusion criteria.

Key Question 3. What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?

No study on the comparative effectiveness of physical activity and weight maintenance among with. mental illness met our inclusion criteria.

Key Question 4. What is the comparative effectiveness of orlistat for the prevention of weight gain among adults?

No study on the use of orlistat and weight maintenance among with mental illness met our inclusion criteria.

Key Question 5. What is the comparative effectiveness of a combination of self-management, dietary, physical activity, and medication strategies for the prevention of weight gain among adults?

One trial (61 randomized, 59 analyzed) of individuals within 6 weeks of the first treatment for a psychotic episode used a combination of self-management, diet, and physical activity strategies for weight gain prevention.106 Subjects were randomized to one of three antipsychotic medications (5 to 20 mg/day olanzapine, 3 to 6 mg/day risperidone, or 3 to 9 mg/day haloperidol) then randomized to either a 3 month behavioral intervention or usual care. The behavioral intervention included individual sessions addressing energy intake and activity behaviors. Subjects received dietary counseling and counseling on an exercise program over 10 to 14 individual sessions, and body weight was measured at baseline, weekly for three months, and at four, six, 12, and 24 months of followup (Appendix E, Evidence Table 29).

BMI Change

Individuals in both the intervention and control groups gained 3.7 kg/m2 during 12 months of followup.106 At 24 months, the intervention group gained 0.5 kg/m2 less than the control group (3.5 kg/m2 gained in the intervention group), although the finding was not statistically significant (Appendix E, Evidence Table 29).

Weight Change

At 12 and 24 months, individuals in the behavioral intervention group gained 10.2 kg and 10.0 kg compared with 11.8 and 11.5 kg in the control group.106 The difference in weight gain met the meaningful between group difference at both time points, but was not statistically significant (Appendix E, Evidence Table 29).

Waist Circumference Change

No study on combination strategies and waist circumference change met our inclusion criteria.

Clinical Outcomes

The trial did not report on mortality or quality of life.

Adherence

The trial did not report on adherence.

Adverse eEvents

The trial did not report on burden of intervention, nutritional deficiencies, eating disorder, activity related injury, adverse effect of medication, or other adverse events.

Subgroups

The trial did not report results by baseline weight, gender, age, life events, race, ethnicity, or cultural group.

Key Question 6. What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults

No study on environment level strategies and weight maintenance among persons with mental illness met our inclusion criteria.