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Loveman E, Frampton GK, Shepherd J, et al. The Clinical Effectiveness and Cost-Effectiveness of Long-Term Weight Management Schemes for Adults: A Systematic Review. Southampton (UK): NIHR Journals Library; 2011 Jan. (Health Technology Assessment, No. 15.2.)

5Discussion

Statement of principal findings

Clinical effectiveness

Twelve RCTs6879 that compared multicomponent interventions with another weight loss intervention or control and which reported results on weight loss in their overweight or obese populations were included. In order to inform practice we attempted to minimise potential differences between studies given the complexity of these types of interventions. A prerequisite for including trials in this review was a minimum length of follow-up of 18 months. This was considered important to enable an assessment to be made of the impact of interventions on sustained weight loss, as weight regain is a known problem associated with weight loss treatment. Another requirement was that studies included in the systematic review needed to have reported their interventions in sufficient detail for them to be reproducible and hence useful to practice. This criterion was also included to allow identification of which, if any, aspects of the components appeared to relate to differences in outcome. However, in practice there were few similarities between the included studies; consequently, the number of meaningful conclusions that can be drawn from the range of studies included is limited (discussed in more detail below).

Five RCTs70,7275 compared multicomponent interventions with non-active comparator groups. In general, weight loss did appear to be greater in the intervention groups than in the comparator groups, although weight losses were relatively small and their clinical meaningfulness is unclear. Where studies measured outcomes at a time point after the active intervention phase, it was seen that the intervention groups began to regain the weight they had lost. Despite this a statistically significant difference in weight loss in favour of the intervention group was maintained in two studies up to 36 months of follow-up.

Two RCTs69,71 compared multicomponent interventions that we classed as having the diet component as their focus. Participants in both studies lost weight, but there were no statistically significant differences in weight loss between study groups. After completing the intervention participants from both studies regained weight over time.

Four RCTs7679 compared multicomponent interventions in which the focus was on the physical activity component. In one study77 participants assigned to the HPA intervention lost more weight at 18 months than those assigned to a SBT intervention, which also included physical activity but with a lower caloric expenditure goal. By 30 months the difference was not statistically significant (the trend remained however). In another study76 weight loss was greater in those in a SBT group than in those in a SBTE group. In the third study79 weight loss was similar between those allocated to a diet and physical activity combined group and those allocated to a diet alone or exercise alone group. In these physical activity focused studies any weight lost was generally small. Data were presented for a subgroup of participants only in the fourth study,78 limiting its value to this review.

One RCT68 compared multicomponent weight loss interventions but the study focus was not on diet or exercise but on other variables. It appeared that weight loss was greatest in participants given daily dietary and exercise goals compared with those given weekly goals. However, no statistical analyses were presented to support this observation. This study suffered from additional methodological limitations.

No studies were identified which used OTC weight loss medications.

In general, weight changes across the included studies were small. The degree of weight loss achieved, however, may be meaningful depending on what threshold is considered a marker of success and from whose perspective it is taken. People who are overweight or obese, and the health professionals involved in their care, may differ in the degree of weight loss they see as ‘significant’. There does not appear to be a consensus as to what would constitute a clinically meaningful weight loss. It is difficult to establish clinical significance because trends in the weight of the general population, the starting weight of individual participants, and the time over which the weight loss is measured would all need to be taken into account. In the studies we included there was a range in the starting weight and BMI of participants (discussed within each section). This might have led to variation in: the ease with which participants lost weight; their perceptions of the importance of losing weight; and their perceptions of meaningful weight loss. If we assume that a 5-kg threshold for the degree of weight loss is meaningful then participants in six68,69,71,73,76,77 of the 12 studies would be considered to have received clinical benefit from their weight loss. An alternative assumption could be that for participants to benefit meaningfully from an intervention any weight loss at the end of the intervention followed by longer-term weight stability would be acceptable. Based on this criterion none of the five studies that presented weight change results at more than one time point would be considered to have demonstrated acceptable weight loss. As there is a natural tendency for weight gain over time in the general population, a further, alternative, assumption could be that no weight regain beyond baseline may be of importance. In this instance all four included studies presenting outcomes over more than one time period would be considered to have shown clinical benefit.70,73,75,77

Cost-effectiveness

Two cost-effectiveness studies that used lifetime chronic disease models to evaluate the diet, exercise and behavioural interventions for overweight and obese people were described.86,87 The models included the costs and benefits, in terms of HRQoL, from avoiding chronic illnesses such as CHD and diabetes. One study was conducted from the perspective of the UK NHS, the Counterweight Programme study,87 and the other was conducted for a societal perspective for a North America health setting.86 There were limitations to both studies and there were omissions in reporting details of the modelling methodology and data inputs which made it more difficult to draw conclusions about the results. The UK study was not based upon an RCT or a systematic review, and so caution is advised in the interpretation of the effectiveness of the intervention. In addition, the costs of the intervention appeared to be underestimated. The Roux and colleagues86 North American study was conducted for overweight and obese women and the intervention costs were much higher than would be expected in the UK. Furthermore, non-medical costs, such as patient time, have been included. Despite the limitations of the studies, the results and methodology of the studies seemed reasonable. Both studies found the interventions to be cost-effective compared with a commonly used threshold of £20,000–30,000 per QALY gained, with estimates varying between −£473 and £7200 ($12,640) per QALY gained.

General discussion

Even though studies in the review of clinical effectiveness were grouped to try to keep the most similar studies together, the studies were still rarely comparable. Differences in the types and durations of interventions, and any subsequent weight maintenance strategies, the length of follow-up, issues around generalisability to the UK and the risk of bias of the studies mean that it is difficult to draw robust conclusions as to the effectiveness of multicomponent weight management programmes. It is also difficult to establish what the core components of such programmes may need to be to maximise and sustain weight loss. With such complex interventions it is difficult to establish with any precision what the ‘active ingredient(s)’ causing any demonstrated effect is. It may be that there are necessary elements to successful weight loss, but with so few data, and so few similarities between interventions, it is difficult to draw any conclusions on this.

As noted earlier we informally assessed all of the studies included in this evaluation in terms of their length of follow-up, sample size, risk of bias, degree of reproducibility of components of the interventions, generalisability and overall effect size (see Appendix 8). Speculatively, the weight loss interventions evaluated by the Stevens and colleagues70,74 studies may offer a useful model for long-term weight management. In particular the Stevens and colleagues70 TOHP-II study, which has a large sample size, reported a statistically significant effect on weight loss at least 24 months after the active intervention, and the intervention appears to be reproducible. In terms of overall methodological rigour, the study was judged to have a generally low risk of bias. It is unclear whether the study was statistically powered to detect an effect of weight change (because the study was powered for reduction in BP); however, the large sample size provides no reason to suspect that the weight change outcome would not have been adequately powered. Its generalisability to the UK is uncertain. Although this study, based on the Trials of Hypertension, had some shortcomings it appears on balance to be best placed among those included in this systematic review to provide a model for further exploration and testing with overweight populations in the UK.

This study had two main phases: an intensive phase (14 weeks) and a maintenance phase (16–18 months), with some maintenance continuing until follow-up at 36 months. The participants' goals were to lose at least 4.5 kg during the first 6 months of the intervention and to maintain that weight loss for the remainder of the trial (participants did regain weight over time but their weight at 36 months remained just lower than at baseline). Key features of the intervention were a calorie-controlled diet with a focus on decreasing consumption of excess fat, sugar and alcohol, a gradual increase in walking, monitoring through self-report (diaries) and at group sessions, and a relatively simple behavioural therapy intervention. This comprised goal-setting or action plans, relapse prevention, self-monitoring and social support. These components appear consistent with recent NICE obesity guideline advice. The extended support and relatively straightforward goals for diet and exercise may be contributing factors to the weight change results shown in the intervention group compared with the usual-care control group but we are unable to test this. However, the resource requirements to deliver an intervention such as this are unclear at the present time as few details were reported in the study publication.

In the studies included in our review the interventions varied in terms of their length, their components, the personnel involved and the ongoing maintenance/support mechanisms involved. For example, if we look at the number of contacts with participants, personnel involved in the interventions saw or had contact with participants weekly for at least 14 weeks in most of the included studies. It is unclear whether this is realistic in terms of the likely resource availability or as an expectation of the participants. In the intervention that we feel may have the most potential for testing in a UK setting70 the intervention was delivered by dietitians and health educators with some input from psychologists. It included 14 weekly sessions, then six biweekly sessions and then three to four monthly sessions during the 18-month intervention and then at least three contacts during the 18-month ongoing support phase. Weight change was generally positive and dropout rates were around 10% in both the intervention and a usual-care control group.

Throughout our report we have commented on issues of generalisability of the populations where appropriate. For example, where the populations are of a certain age or gender, have answered media advertisements for entry into the studies and/or paid deposits to do so and the fact that none of the studies were carried out in a UK setting and so may have different health systems and populations. A potential example of a more generalisable intervention is the Counterweight Programme.87 This is currently being rolled out in primary care in many areas of the UK. However, the evaluation of the Counterweight Programme87 intervention was based on a non-randomised study and thus did not meet the inclusion criteria for our systematic review of clinical effectiveness. We are therefore unable to ascertain whether the intervention is clinically effective. The economic evaluation of the Counterweight Programme87 was summarised in our systematic review of cost-effectiveness studies and appeared to be cost saving. However, caution in interpretation is required as the study did not meet the inclusion criteria for this review and there were uncertainties around estimates of the costs of the programme and around assumptions about the extrapolation of effectiveness estimates over time.

Comparison to existing systematic reviews

We have identified 10 existing systematic reviews that focused on weight management interventions for adults (see Table 6). All of these systematic reviews had included studies of interventions comprising diet, exercise and/or behavioural components, but none specifically included only studies with all three components as recommended in the NICE obesity guideline. There appeared to be a consensus from these systematic reviews that the most effective weight loss interventions were those that were multicomponent. Only one of these existing systematic reviews looked specifically at long-term evidence of the interventions, but its aims and inclusion criteria were different to those of our systematic review, precluding comparisons.

Other issues and methodological concerns

The scope of this review was to focus on studies that would be of most use to policy and practice. We therefore sought studies with long-term follow-up and in which the interventions were clearly described (to enable replicability). Despite this, we identified evaluations of a range of different multicomponent interventions, making it difficult to compare results and to make meaningful conclusions. There are a number of other factors that should also be considered in the interpretation of the studies.

Weight regain was common among participants in the included interventions, even in studies with extended ongoing support. Unfortunately, the data available do not allow us the opportunity to offer any inference as to what might be causing this and it is unclear whether this is clinically meaningful in some way.

Incentives to recruit people to participate were used in three of the included studies.72,73,79 Although not directly tested it does not appear that there was any relationship between using incentives and the likelihood of weight change.

Our review aimed to comment on any particular barriers to or facilitators of weight loss that may help to establish what the key components of these types of interventions should be, but the evidence we reviewed offers no insights into this. From the available data it is not possible to determine whether the weight loss interventions had any negative effects on participants.

Weight loss success may depend on whether trial participants have previously attempted weight loss or how long they have experienced overweight or obesity. Data on these factors could potentially be used to target interventions to certain populations. We attempted to capture these data; however, treatment history was only reported in three72,75,76 of the included studies and the duration that participants had been overweight or obese was not reported in any study. As such there are not enough data for us to reflect on any patterns in the results seen.

Even in those studies with a non-active comparator (e.g. usual care) it was difficult to establish the true estimate of the effects of an intervention as very few studies adequately described their non-active comparator. It seems likely that participants assigned to control arms would still have received some contact with health-care professionals, which may have the potential to underestimate the treatment effect.

The methodological quality of the included studies varied. None of the studies reported all the details necessary to assess all 10 of the quality assessment criteria that we used. In most studies fewer than half of the criteria could be adequately assessed. Similarly, between the included studies there were no individual quality assessment criteria that were reported by all of the studies. A recent systematic review91 of 63 RCTs of any intervention for weight loss found that while reporting seemed to have improved since the publication of the revised consolidated standards of reporting trials (CONSORT) statement in 2001, reporting of some key aspects was still poor. In the review, 60% of the overall CONSORT criteria were satisfied by the RCTs, but the reporting of criteria relating to the methods varied, with just 19% of studies satisfying the reporting criteria relating to treatment allocation. The authors of that systematic review suggest that there is considerable room for improvement in the adherence to the CONSORT reporting criteria.

Many studies included in our evaluation were undertaken more than 10 years ago. It is likely that this would have had a bearing on the reporting of methods used in the studies and the interpretation of results. For example, the general population today is more exposed (e.g. by mass media) to the issue of overweight and obesity and, as a result, likely to be more aware of healthy eating and physical activity messages. It is therefore possible that the effect of interventions conducted a decade or more ago might not be so large in the present day. Over time the roles of health professionals may also have changed, so the types of people delivering weight management interventions today may be different from those who would have delivered such interventions in the past. Practice may also vary geographically, including within countries. The studies in our review provided little detail on the process of training providers.

In the two studies86,87 that were described in our cost-effectiveness review the costs of the multicomponent weight loss programme varied between £60 and US$3040 (£1820) per participant. The costs reported in the other reviews for weight programmes appear also to be within this range. A NICE guidance report35 for the management of obesity included a review of diet, exercise and behavioural treatment and the resource costs for these components. In the NICE report, physical activity interventions cost between £532 and £737; diet interventions cost between £103 and £621; and a diet and behavioural intervention cost £672 per patient. One study included in the NICE review of a pharmacological trial for sibutramine included diet and exercise advice as the control arm with a cost of £243.48 per person.92 Avenell and colleagues30 reviewed treatment for obesity and constructed an economic model for a diet and exercise intervention for individuals with impaired glucose tolerance. The total estimated cost for the LI was £324 per person in the first year and £178 per person for subsequent years. The resource costs reported for other weight loss interventions seem to concur with our conclusion that the costs in the Counterweight Programme study87 are too low, and those from the Roux and colleagues North American study86 do not reflect UK costs.

The gain in QALY compared with routine care varies considerably between the two studies86,87 due to the differences in the assumptions for long-term weight loss maintenance and the utility values chosen for weight change. The change in utility values associated with a unit change in BMI varied between about 0.006 for the Counterweight Programme87 and 0.02 for Roux and colleagues.86 Neither study based these utility estimates upon a review of the QoL literature. A recent Health Technology Assessment report33 on the clinical effectiveness and cost-effectiveness of bariatric surgery for obesity conducted a targeted search to identify published utility estimates for BMI values relevant to obese adults. The authors of this study stated that the values from the study by Hakim and colleagues93 represented the most methodologically sound estimates derived. Hakim and colleagues93 found that a one-unit decrease in BMI in obese individuals without diabetes was associated with a gain of 0.017, which was independent of age or gender. The utilities values from this study are consistent with those chosen by Roux and colleagues,86 but much higher than those used by the Counterweight Programme study, suggesting that the Counterweight Programme study may be underestimating some of the health gain associated with weight loss. However, although the QALY gains are small in these studies, the interventions are still cost-effective by generally accepted thresholds, because the interventions have such low costs.

One of the studies discussed in our review (Roux and colleagues86) included a utility decrement associated with the effort involved with participating in a weight management scheme. This resulted in the situation where participants of a diet-only strategy had lower lifetime QALY than those having routine care. As the primary data analysis to derive these data was not reported, it is unclear how these data were derived and whether the assumptions are valid. Removing this assumption would result in a more favourable cost-effectiveness estimate.

The cost-effectiveness results in the two studies described in our cost-effectiveness review are consistent with other cost-effectiveness studies for diet and exercise interventions (but without a behavioural component). Gallani and colleagues94,95 described a Markov model for a diet and exercise intervention in Switzerland in overweight and obese people. In their analysis the diet and exercise intervention was cost-effective for all subgroups with an ICER < £5000 per QALY. Bemelmans and colleagues96 described a cost–utility study in the Netherlands in overweight and obese people. The ICER for the diet and exercise intervention was €7400 (£6700) per QALY saved. Furthermore, a NICE review35 for diet, exercise and behavioural treatments concluded that ‘the cost per QALY in the best-performing non-pharmacological studies ranges from £174 to £9971’. This suggests that even though there were limitations to each of the studies in our cost-effectiveness review, the results appear to be consistent with other studies.

Strengths and limitations

This review has the following strengths:

  • It is independent of any vested interest.
  • It has been undertaken following the principles for conducting a systematic review. The methods were set out in a research protocol (see Appendix 1), which defined the research question, inclusion criteria, quality criteria, data extraction process and methods to be employed at different stages of the review.
  • An advisory group has informed the review from its initiation. The research protocol was informed by comments received from the advisory group and the advisory group has reviewed and commented on the final report.
  • The review brings together the evidence for the clinical effectiveness and cost-effectiveness of long-term weight management schemes for adults who are overweight or obese. This evidence has been critically appraised and presented in a consistent and transparent manner.

In contrast, this review also has certain limitations:

  • Synthesis of the included studies was through narrative review. Although 12 studies were included in the review of clinical effectiveness, differences in the interventions meant that meta-analysis was inappropriate.
  • No cost effectiveness or cost-effectiveness studies were found which met our full inclusion criteria and we therefore took a pragmatic approach to discuss two studies that met many of the attributes our review was looking for. Caution is therefore required in the interpretation of our results in terms of cost-effectiveness.
  • Searches were limited to the English language. Therefore, we may have omitted non-English language, but otherwise includable, studies from our review.
  • Many studies were excluded from our review because they either did not include a behavioural therapy element or they reported that there was a behavioural element but did not provide any details of how this was implemented. Although we attempted to contact authors of a number of studies to try to ascertain further details, this was unproductive. It may be that there are other studies with a long-term view of a weight management intervention that we were therefore unable to include. However, it is also apparent that the term ‘behavioural’ appears to be used in many situations to mean that a study aimed to change behaviours, but that this was as a result of the diet and/or exercise intervention components rather than of a specific behavioural therapy. It is unclear whether this is the case in any of these situations.

Need for further research

There have been a number of RCTs of multicomponent weight management interventions, and despite a number of differences between the many studies, there does appear to be some degree of success in general. It is uncertain whether any one particular intervention is best; however, the results of our review suggest that the TOHP intervention70,74 may be useful for testing further in a UK population. If any future RCT takes place, then replicating the intervention used in the TOHP study should be considered.

As most interventions succeeded in short-term weight loss, more research into the most appropriate long-term support to improve long-term maintenance of weight loss is required. Researchers should consider the Medical Research Council framework for developing evaluations of complex interventions97 and the National Obesity Observatory standard evaluation framework for weight management interventions98 when they design their studies.

There is a need for information on barriers to and facilitators of weight change in weight management interventions to be reported and, if possible, evaluated in clinical trials. As well as providing useful evidence on individual factors associated with greater or lesser weight change, such information could assist understanding of which of its components a multicomponent intervention should focus on.

There is a need for better reporting of behaviour therapy interventions, in terms of clear details of the techniques used, theoretical model, the format, setting and provider.62 Authors of studies should more critically consider the reproducibility of their interventions. A taxonomy of a variety of behaviour change techniques has been devised and tested, to facilitate a common classification by intervention providers and researchers.57 It would be advantageous for future evaluations to employ such a system in the reporting of interventions to facilitate a greater understanding of the specific components of interventions associated with effective health-related behaviour change.

An economic model for weight management interventions is needed for the UK NHS that includes a complete explanation of model structure, assumptions and data inputs. This model should be based upon evidence of the intervention effect, from an RCT or systematic review, with UK-relevant data inputs, particularly with regard to costs.

© 2011, Crown Copyright.

Included under terms of UK Non-commercial Government License.

Cover of The Clinical Effectiveness and Cost-Effectiveness of Long-Term Weight Management Schemes for Adults: A Systematic Review
The Clinical Effectiveness and Cost-Effectiveness of Long-Term Weight Management Schemes for Adults: A Systematic Review.
Health Technology Assessment, No. 15.2.
Loveman E, Frampton GK, Shepherd J, et al.
Southampton (UK): NIHR Journals Library; 2011 Jan.

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