Authors' objectives:

The objectives of this review were: 1. To review systematically obesity treatments in adults to identify therapies that impact by achieving weight reduction, risk factor modification or improved clinical outcomes. 2. Based on a systematic review of epidemiological data, to model the impact of moderate weight reduction on reducing the burden of obesity-associated disease. 3. To review systematically health economic evaluations of obesity treatments and assess costs to the NHS of these treatments. 4. To integrate the findings from the above objectives.

Authors' results and conclusions: Limitations in the evidence available for the reviews, particularly inadequate sample size and reporting, lack of long-term follow-up and few quality of life data, mean that most results should be interpreted with caution. First, regarding the addition of drugs to the diet, orlistat was associated with a weight change of 3.26 kg [95% confidence interval (CI) 4.15 to 2.37 kg] after 2 years, and beneficial changes in risk factors. Sibutramine was associated with a weight change of 3.40 kg (95% CI 4.45 to 2.35 kg) after 18 months for people on a weight maintenance diet and beneficial changes in risk factors apart from diastolic blood pressure. Metformin was associated with decreased mortality and myocardial infarction-related mortality in the UK Prospective Diabetes Study after 10 years. Low-fat diets (which included 600 kcal/day deficit diets) were associated with the prevention of type 2 diabetes, and improved control of hypertension. These diets were associated with a weight loss after 12 months of 5.31kg (95% CI 5.86 to 4.77 kg) and improvements in risk factors, with weight loss continuing for 3 years. Insufficient evidence was available to assess putative benefits of low-calorie or very low-calorie diets. Studies combining low-fat diets and exercise, with or without behaviour therapy, suggested improved control of hypertension and type 2 diabetes. The addition of an exercise programme to diet was associated with improved weight loss and risk factors for at least 1 year. The addition of a behaviour therapy programme to diet was also associated with improved weight loss for at least 1 year. It was unclear whether both exercise and behaviour therapy together further enhanced the effect of diet. Family therapy was associated with improved weight loss for up to 2 years compared with individual therapy. However, there was insufficient evidence to conclude that individual therapy was more beneficial than group therapy. Second, women with obesity-related illnesses, who had intentional weight loss, irrespective of the amount of weight lost, had an associated reduced risk of death, CVD death, cancer and diabetes-related death. Weight loss appeared more beneficial if achieved within 1 year. Men with general illness who lost weight intentionally appeared to have a reduced risk of diabetes-related death, but there was no demonstrable effect on CVD mortality, and cancer mortality appeared increased. Long-term weight loss was associated with reduced risk of developing type 2 diabetes and improved glucose tolerance in men and women, especially after surgery for obesity. A weight loss of 10 kg was associated with a fall in total cholesterol of 0.25 mmol/l and a fall in diastolic blood pressure of 3.6 mmHg. A weight loss of 10% was associated with a fall in systolic blood pressure of 6.1 mmHg. Third, targeting high-risk individuals with drugs or surgery was likely to result in a cost per additional life-year or quality-adjusted life-year (QALY) of no more than 13,000 GBP. There was also suggestive evidence of cost-saving from treatment of people with type 2 diabetes with metformin. Targeting surgery at people with severe obesity and impaired glucose tolerance was likely to be more cost-effective, at 2,329 GBP per additional life-year. Economic modelling of diet and exercise over 6 years for people with impaired glucose tolerance was associated with a high initial cost per additional QALY, but by the sixth year the cost per QALY was 13,389 GBP. Results were sensitive to the quality of life weights, for which there were very limited data. Results did not include cost savings from diseases other than diabetes, and therefore may be conservative. The cost of diet and exercise together appear comparable to treatments, for example drugs, in obese individuals with risk factors, such as impaired glucose tolerance.

Authors' recommendations: Orlistat, sibutramine and metformin appear beneficial for the treatment of adults with obesity. Exercise and/or behaviour therapy appear to improve weight loss when added to diet. Low-fat diets with exercise, with or without behaviour therapy, are associated with the prevention of type 2 diabetes and hypertension. Long-term weight loss in epidemiological studies was also associated with reduced risk of developing diabetes, and may be beneficial for cardiovascular disease. Low-fat diet and exercise interventions in individuals at risk of obesity-related illness, such as diabetes, are of comparable cost to drug treatments.

Authors' methods: Systematic review, Economic evaluation

Project Status: Completed

URL for project: http://www.hta.ac.uk1187

Year Published: 2004

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: England, United Kingdom

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk

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