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Hutfless S, Maruthur NM, Wilson RF, et al. Strategies to Prevent Weight Gain Among Adults [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2013 Mar. (Comparative Effectiveness Reviews, No. 97.)

Introduction

Background

Condition

One of the Healthy People 2020 national objectives is to increase the prevalence of a healthy weight among adults to 34 percent and reduce the prevalence of obesity among adults to less than 30 percent.1 From 2005 to 2008, only 31 percent of adults were at a healthy weight.2

Body mass index (BMI) (see Appendix A for a list of acronyms) – expressed as weight in kilograms divided by height in meters squared (kg/m2) – is commonly used to classify underweight (BMI <18.5 kg/m2), healthy or normal weight (BMI 18.5–24.9 kg/m2), overweight (BMI 25.0–29.9 kg/m2), obesity (BMI ≥30.0 kg/m2), and extreme obesity (BMI ≥40.0 kg/m2).

The estimated age adjusted prevalence of overweight and obesity (BMI ≥25.0 kg/m2) was 68 percent in the United States (U.S.) from 2007 to 2008. Despite the doubling in the prevalence of obesity between 1976 to 1980 and 2007 to 2008 (13 to 34 percent), the prevalence of overweight has remained stable between the same time periods (32 to 34 percent). The largest increase in obesity during these times was among Americans who live 200 percent or more below the poverty line.3 Those people living below the poverty line are more likely to live in areas without grocery stores and have fewer places to exercise than individuals who live in more affluent neighborhoods.4

Progression to Obesity From Healthy Weight Can Occur Gradually Over Time

Adults tend to gain weight progressively through middle age. Although the average weight gained per year is 0.5 to 1 kg, the modest accumulation of weight over time can lead to obesity.5 During 2009 to 2010, 33 percent of men and 32 percent of women age 20 to 39 were obese, compared with 37 and 36 percent at age 40 to 59 and 37 and 42 percent at ages 60 and older.6

Obesity Differs by Sex and Ethnicity

The sex specific prevalence of obesity was 32 percent of men and 36 percent of women during 2007 to 2008 in the U.S. The prevalence of obesity is greater among non Hispanic Blacks and Mexican Americans than non Hispanic whites.7 Access to healthy food and places to exercise, as well as cultural differences, may contribute to the differences in obesity prevalence.4,8

Obesity Increases Morbidity and Mortality

Obesity is a risk factor for chronic conditions including cardiovascular disease, type 2 diabetes, arthritis, certain types of cancer, and cancer recurrence.9-16 Weight is associated with an increased risk of some forms of cancer and cancer recurrence. There is growing evidence that breast cancer survivors or women with breast cancer have better outcomes if they lose or maintain their weight. Obesity can also be caused by medications used to treat chronic disease as is the case for antipsychotic treatments,17 some type 2 diabetes treatments,18,19 and tamoxifen and aromatase inhibitors to treat or prevent breast cancer or cancer recurrence.20 Higher grades of obesity are associated with excess mortality, primarily from cardiovascular disease, type 2 diabetes, and certain types of cancer.21

Obesity Economically Impacts the U.S. Health Care Systems

Obesity was estimated to cost $79 billion in the United States during 1995. By 2008, obesity costs rose to $147 billion. The Federal Government pays about half of the cost of obesity and its associated conditions through Medicaid and Medicare spending.22

Strategies To Prevent Progression to Obesity Among Adults Are Needed

Because the health outcomes for overweight individuals may be more like those of healthy weight individuals than those with obesity, factors associated with the maintenance of overweight are also of interest to serve as intervention points to prevent obesity. Maintenance of non obese weight is considered to be an adult weight between a BMI of 18.5 and 29.9 kg/m2 with long term stability within this range.

Strategies to Prevent Progression of Further Obesity Among Adults Are Needed

Adults who have the greatest degree of obesity have higher morbidity and mortality than those whose weight is closer to overweight.21 For example, adults with a BMI 40 kg/m2 or greater have more co morbidities than those with a BMI of 30 to 39 kg/m2,1 and adults with a BMI greater than 35 kg/m2 have more mortality than those with a BMI of 30 to 34 kg/m2.2 Maintaining an obese weight closer to overweight may be advisable compared with maintaining an obese weight that is progressing to more extreme obesity.

Strategies To Prevent Weight Gain

Multiple strategies have been investigated to identify strategies to effectively maintain weight among adults. These strategies include self management techniques, diet, physical activity, medications, or combinations of these strategies at the individual or community level.

These strategies have been implemented in multiple settings, including clinical care settings, community settings, higher education settings, and workplaces.

Some strategies have targeted individuals at high risk of gaining weight because of a family history of obesity or diabetes mellitus, a diagnosis of these chronic conditions, or because of use of a medication that contributes to weight gain,23 while others have more inclusive enrollment criteria or are directed at an entire population.24,25

Self-Management Strategies To Prevent Weight Gain

Self-management strategies may include goal setting, self monitoring, problem solving, relapse prevention, and stimulus control.26 Other strategies may include regulating the time spent watching television or sleeping, enhancing self care, or acquiring social support. Weight loss studies suggest that frequent contact with interventionists and self monitoring of weight may be particularly valuable.27 However, participants recruited to studies to prevent weight gain may have less motivation to change their behavior than those recruited to weight loss studies because of the absence of obesity and obesity related disease.27 As a result, the robust literature on self-management strategies to lose weight and maintenance of weight after loss cannot be applied directly to weight gain prevention.27

To date, the most effective elements of behavioral strategies for weight maintenance are not known. From a public health perspective, less intensive interventions27 and strategies targeting patients at high risk of complications from weight gain are of great interest.

Dietary and Physical Activity Strategies To Prevent Weight Gain

Individuals who are successfully maintaining their weight are successfully balancing energy (kilocalories) intake and energy expenditure. These individuals maintain energy balance by having a consistent intake of adequate, rather than excess, kilocalories.28 Some use specific dietary patterns (e.g., low fat or low carbohydrate).29 Adequate energy expenditure may also come from integration of physical activity into everyday activities or from making time for exercise in the daily routine.29

To date, the types of diet and physical activity strategies used for weight gain prevention have not been systematically evaluated. Specific dietary strategies of interest include eating patterns, macronutrients (such as fiber) from food sources, micronutrients from food sources, and any physical activity strategies such as walking, running, biking, or a training program. Physical activity has cardiovascular and psychological health benefits, making it a suitable strategy for individuals with existing chronic diseases or mental health concerns.30,31

Medications To Prevent Weight Gain

In the U.S., there are several medications approved for weight control in individuals with a BMI of 27 kg/m2 or higher. The dietary fat absorption inhibitor, orlistat, has been shown to help maintain weight loss and improve cardiovascular risk factors with continued, long term use.32 Because the sympathomimetic amines (i.e., phentermine or diethylpropion) are only approved by the U.S. Food and Drug Administration for short term use under the indication of weight loss, they are not appropriate for this review.33

Orlistat is a lipase inhibitor available without a prescription.34 The accessibility of orlistat makes is possible that individuals may use it for weight maintenance independent of weight loss in overweight and obese populations. To identify if orlistat's effectiveness is being tested in these individuals and because orlistat is approved for long term use, the only medication of interest for the review was orlistat.

Environment-Level Strategies To Prevent Weight Gain

The built environment encompasses all of the buildings, spaces, and products created or modified by people.35 Built environment strategies are applied at the community level and affect the environment that a community interacts within.

Built environment strategies may be implemented in multiple settings. Examples of built environment strategies include fast food outlets and corner food stores posting calories or increasing the availability of fresh food. At the neighborhood level built environment strategies may include increasing sidewalks or planting trees to improve walkability. Strategies may be directed toward individuals at high obesity risk such by implementing strategies in communities that include a greater prevalence of low income minority populations. Built environment strategies may also occur within a workplace or school where a subset of the population has access to them.

A previous systematic review that aimed to identify policy studies about weight maintenance, including environment level strategies, did not report identifying any such studies.36 However, the review did not include serial cross sectional or time series studies. A national policy research group, PolicyLink, recently published a report on the impact of access to grocery stores on health related outcomes.37 The authors identified several peer reviewed manuscripts that reported weight as a health related outcome of interest as measured in cross-sectional studies. Weight change was not a priority outcome for the report.

Current Controversies in Weight Gain Prevention

Previous systematic reviews have concentrated on weight loss or maintenance of weight after weight loss.38,39 Strategies that are effective for preventing weight gain may be different than strategies that are useful for weight loss or for maintenance of weight after weight loss.

Systematic reviews on the prevention of weight gain or weight maintenance are lacking. Previous systematic reviews on weight gain prevention have allowed the inclusion of studies targeting weight loss in the non obese36 and included studies that were as short as 6 months.27

Synthesis of the predictors of longer term weight gain prevention is needed. Accounting for adherence to weight gain prevention interventions is also needed. Because an intervention can only be effective among those who adhere to it, adherence is an intermediary between the intervention and its effect on long term weight maintenance.

Treatment Guidelines and Meta-Analyses on Weight Gain Prevention

We identified no treatment guidelines for maintenance of weight, although several guidelines and systematic reviews address the maintenance of weight after weight loss.6,38-42 Only one previous review with a meta analysis evaluated obesity prevention. The review was conducted as background for a study on the impact of cancer prevention interventions on obesity prevention.36 The primary outcome of interest for the meta analysis was the difference in change in BMI or body weight between the intervention and control groups among studies published from 1996 to 2006 that listed a specific goal of weight gain prevention or weight maintenance in the design of the original trial.

A 2010 Cochrane review examined workplace based diet and physical activity interventions and change in BMI from baseline among non obese and obese employees.43 The investigators found that the interventions decreased weight by 1.3 kg, on average, at 6 to 12 months of followup and that BMI decreased by 0.5 kg/m2. The findings are reported as recommendations to implement workplace interventions for controlling overweight and obesity in the Task Force on Community Preventive Services.6

Scope and Key Questions

Scope of the Review

The goal was to compare the effectiveness, safety, and impact on quality of life of independent and combined strategies to prevent weight gain among healthy weight, overweight and obese adults. Studies that evaluated interventions targeting a combination of weight loss with weight maintenance, or weight loss exclusively, were excluded. We also excluded studies to prevent excessive weight gain during pregnancy because for normal weight women, weight gain is expected during pregnancy.

The specific Key Questions (KQ) are:

KQ1:What is the comparative effectiveness of self-management strategies for the prevention of weight gain among adults?
KQ2:What is the comparative effectiveness of dietary strategies for the prevention of weight gain among adults?
KQ3:What is the comparative effectiveness of physical activity strategies for the prevention of weight gain among adults?
KQ4:What is the comparative effectiveness of medications for the prevention of weight gain among adults?
KQ5: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?
KQ6:What is the comparative effectiveness of environment level strategies for the prevention of weight gain among adults?

We planned to include studies of adults, including various subgroups of individuals at high risk of weight gain, which compared self management, diet, physical activity, use of orlistat, or a combination of these strategies over at least one year. Dietary and physical activity strategies inherently include some aspects of self-management. Only when self-management did not include traditional diet or physical activity components (i.e., daily weighing or regulating television viewing) was the study reported in KQ1. We compared the outcomes of weight, BMI, waist circumference, obesity related clinical outcomes (mortality, health related quality of life, and cancer recurrence), and adverse effects (Table 1 and Figure 1).

Table 1. Characteristics of the target studies according to the PICOTS framework.

Table 1

Characteristics of the target studies according to the PICOTS framework.

Figure 1 describes the framework used to develop and implement this project which aims to describe how adult weight outcomes (BMI, weight, waist circumference, progression to overweight or obese) are impacted by interventions (self-management, diet, physical activity, medication, combinations, or built-environment). Intermediate outcomes of interest include adherence, and use of environmental modification. Clinical outcomes include, mortality, cancer, cardiovascular disease, sub-fertility, diabetes, degenerative joint disease, liver disease, and quality of life. Adverse effects include burden of the interventions, nutritional deficiencies, eating disorders, activity-related injury, adverse effect of medication, and other.

Figure 1

Analytic framework for comparative effectiveness of strategies to prevent weight gain among adults. BMI = body mass index; KQ = Key Question

Cover of Strategies to Prevent Weight Gain Among Adults
Strategies to Prevent Weight Gain Among Adults [Internet].
Comparative Effectiveness Reviews, No. 97.
Hutfless S, Maruthur NM, Wilson RF, et al.

AHRQ (US Agency for Healthcare Research and Quality)

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