Treating obesity in individuals and populations

Introduction

Although interest in and funding to treat obesity have increased,1 its prevalence has not yet decreased. In this review I summarise the evidence behind interventions to treat or prevent obesity in adults, children, and communities; discuss the strengths and weaknesses of current research; and recommend a direction for future treatment and research.

Methods

I systematically searched the literature during January 2004 and synthesised the results of systematic reviews of obesity treatment and prevention. The methods and results are fully described in the monograph “What works for obesity?” (www.unitedhealthfoundation.org/obesity.pdf).

What has been studied?

Studies of lifestyle interventions or a combination of diet and exercise were most common.2 A few treatment programmes involved simple interventions (such as giving brief advice to decrease fat intake), but most did not. Most addressed both diet and physical activity and often had an educational component—behavioural therapy, incentives for attendance and weight loss, or help from family members and health professionals.2 In general, they were time and labour intensive—and therefore probably expensive, although costs were not reported.

Most of the research focused on adults and on individual treatment in a clinical setting.3 Despite the need to address eating and activity habits in early life, research about prevention and treatment of childhood obesity was meagre.4 5

Few studies evaluated the effectiveness of environmental or policy initiatives. Some referred to changes made in the participants' environment, but these were not described in detail and their impact was not analysed separately from that of the main treatment.2 None of the systematic reviews of environmental interventions reported in the literature assessed weight measures as outcome variables.6

Do any treatments work?

Even “effective”dietary and exercise treatments for adult obesity produced modest weight loss (about 3-5 kg) compared with no treatment or usual care.2 3 7 Weight loss drugs such as sibutramine and orlistat, used in conjunction with diet or exercise programmes, also produced 3-5 kg of weight loss, but the effects often did not last after the drug was stopped.3 8^–10 Although the weight loss of 3-5 kg was statistically significant and had some health benefits,11 its clinical significance was not shown—that is, it may not have been enough to improve the health or quality of life of patients. In most studies with long term follow-up, the weight lost initially gradually came back.

For patients with severe obesity, surgery was effective. Gastric surgery resulted in 25-44 kg weight loss up to two years after the operation, and 20 kg loss up to eight years later.12 13

For treating children, no interventions were definitively effective, although strategies that reduced sedentary behaviour (particularly television watching) and involved parents showed the most encouraging results.4 5 14

Only a few studies assessed attempts to prevent obesity among adults, children, or communities.2 These were mostly educational campaigns to motivate individuals, sometimes including environmental changes such as altering food options in grocery stores or schools. None resulted in weight loss.

How good is the evidence?

I assessed the research against the standards for evidence based medicine for interventional studies.15 16 Most studies were randomised controlled trials, systematic reviews of randomised controlled trials, or, when randomisation was not ethical or feasible, well controlled prospective studies. Although these were the best studies available according to the principles of evidence based medicine, many did not fulfil its requirements. For example, randomised trials often lacked details describing the randomisation and were seldom blinded. Participants were usually few in number, not well characterised at baseline, and rarely diverse (most were white, well educated women). Attrition rates were high, and intention-to-treat analysis was seldom conducted. Participants were generally not followed long enough to ensure that weight loss was permanent. These flaws bias the results and can exaggerate the effects. Systematic reviews noted the lack of high quality clinical trials and recommended that future studies should fulfil the requirements of evidence based medicine.4 5

Where do we go from here?

Treating individuals

The available research shows that surgery is an effective treatment for severe obesity. Drug treatments have not made a substantial difference in obesity rates. Lifestyle interventions have been called effective but have resulted in only small amounts of permanent weight loss with marginal clinical relevance, despite participants' gains in knowledge and skills. Future studies should include assessments of patient centred outcomes such as satisfaction with the result or quality of life. Of the successful interventions, it would be worthwhile identifying those that required the least effort. Any programmes that could show that weight loss continued beyond the end of the intervention deserve extra attention.

Advertising and the lay literature abound with dieting “success stories.” Although most of these may seem scientifically implausible or exaggerated, consumers flock towards products or strategies that offer even a small hope of success. Meanwhile, the scientific community interested in lessening obesity has been noticeably silent both about discounting the false claims made by advertisers and publishing the data behind real successes. To find non-surgical treatments that result in substantial weight loss, we must fully characterise true obesity treatment successes. The National Weight Control Registry in the United States has information on individuals who have lost substantial amounts of weight and kept it off17; qualitative and quantitative research on these and other real success stories could be translated into practical strategies for weight loss and maintenance.

Learning how some people avoid getting obese despite living in an obesity promoting environment could yield clues for effective interventions

© RICHARD KALVAR/MAGNUM PHOTOS

It may also be helpful to pose the question differently. Why are some people not obese despite living in an obesity promoting environment? Lean individuals have probably found ways to moderate eating habits and to exercise regularly, but knowing the details of how they achieve these practices could be revealing. Do they exercise every day, do they ever dine at restaurants? Do they hike in the mountains on weekends or walk to school with their children? How and at what age did they develop their good eating and exercise habits? Detailed qualitative research to investigate the factors that help protect high risk people (such as those with obese parents) in particular from becoming obese may help us to understand the key biological, social, and environmental factors leading to successful weight control.

Conclusion

Rather than showing what does work for preventing and treating obesity, research to date shows us clearly what does not. A thorough search of the available evidence reveals that obesity research has been targeted mainly at individuals and that most interventions result in only small amounts of weight loss and have little impact on the obesity epidemic. Ironically, most experts agree that the obesity epidemic is environmental, but the research has largely ignored this factor.24 It is time to be realistic with individuals about the limited effectiveness of lifestyle interventions and obesity drugs, and to focus on public health interventions rather than individual treatments to halt the obesity epidemic.

This article is based on the monograph “What works for obesity? A summary of the evidence behind obesity interventions,”which was published in association with Clinical Evidence by the BMJ Publishing Group and commissioned, funded, and distributed by the United Health Foundation.. I thank Matt M Davis and Boyd Swinburn for reviewing earlier versions of this manuscript and offering helpful comments.