To assess the scientific evidence underlying the interventions against obesity in adults and children. The Project Group reviewed the evidence for preventive interventions and a range of treatment methods, including diet, exercise, behavioral therapy, medications, alternative medicine, and surgery.
Systematic literature reviews
The Project Group systematically searched the MEDLINE and Cochrane Library databases for scientific literature published on obesity between 1996 and 2001. A search for literature addressing costs and economic assessments was conducted in the Cinahl, MEDLINE, HEED, and NHS Center for Reviews and Dissemination databases. The search for literature on alternative medicine also included the EmBase and Cinahl databases, and PsycInfo was used to search the literature on ethics and quality. Further complementary searches were conducted using the reference lists in relevant articles, conference reports, the Project Groups international contacts, and review articles.
The literature review and quality evaluation was done in several steps. Initially, the relevant studies were selected by two Project Group members, independently of each other, according to pre-established criteria. Any differences in judgement were discussed and a consensus was reached. The quality evaluations were conducted using a review format with pre-established criteria. All studies were graded by two members from the Project Group, and the value of the evidence presented was ranked as high, moderate, or poor. In cases where agreement could not be reached, a third member from the group read the article, and a decision was made following discussion. Thereafter, facts were extracted from the studies. A synthesis of the results, particularly from the studies that received a high or moderate grade, was carried out and conclusions were drawn. Only statistically significant differences (p>0.05) in the results were reported.
Finally, the conclusions in the report were graded in accordance with a set of pre-established criteria indicating the strength of the evidence: strong scientific evidence (Grade 1), moderate scientific evidence (Grade 2), and limited scientific evidence (Grade 3). For further details, please refer to the report.
- The prevalence of obesity and its complications is increasing rapidly.
The number of individuals with obesity (both adults and children) has increased substantially during the past 20 years, and approximately 500 000 individuals in Sweden are now obese. Obesity - particularly when localized to the abdomen - is associated with an increased risk for several serious diseases, eg, diabetes, cardiovascular diseases, and joint disorders. The correlation between obesity and certain types of cancer is strong. Obesity – particularly severe obesity – also has a strong negative influence on the quality of life.
- The causes for obesity are only partly known.
The development of obesity depends, to a great extent, on genetic factors. Genetic predisposition for obesity is widespread in the population. When the individual is genetically predisposed, then lifestyle (diet and exercise), social, behavioral, cultural, and community factors determine whether or not obesity develops.
- It is difficult to prevent obesity.
Most population-based preventive programs that have been scientifically assessed have not demonstrated any favorable effects on the prevalence of obesity. However, there are examples of successful programs for both adults and children. New outreach strategies - eg, to disseminate the latest information about the causes and risks of obesity and to change dietary habits and motivate individuals to become more physical active - need to be developed and assessed. Concurrently, public policy initiatives are needed to reduce the incidence of obesity.
- Scientific assessments of treatment methods for obesity show that:
- Changes in dietary habits through counseling (mainly reduction of energy and fat intake) can lead to weight reduction, as a rule in the range of 3 to 10 kg during the first year (or 10% of body weight in children). The long-term effects are uncertain.
- Regular exercise contributes to weight reduction.
- Behavioral therapy in conjunction with changes in diet and exercise can have further effects on weight if supportive interventions continue for a longer period.
- Approximately one fifth of those who undergo treatment based on the weight watcher approach, and reach their goals, achieve a permanent weight loss of 10% or more of their original weight.
- VLCD for 6 to 12 weeks yields a greater weight reduction than conventional low energy diets. In studies of VLCD for 1 to 2 years, where the treatment was often periodic, authors note a retained weight loss of a few kilograms more than in treatment using a balanced diet alone (VLCD = Very Low Calorie Diet, based on protein formulas).
- Pharmacological treatment using orlistat (Xenical®) or sibutramine (Reductil®) yields an average weight loss of 2 to 5 kg beyond that which would be attained through diet and exercise alone. In clinical trials, one fourth to one fifth of those who started pharmacological treatment lost at least 10% in weight compared to half as many of those treated with placebo.
- The major problem is that weight loss is not usually permanent. Within a few years most who had initially succeeded in losing weight had returned to their original weight. Therefore, it is particularly important to develop and assess long-term treatments that aim at permanent weight loss.
- Surgical treatment, which is an option in severely obese patients, reduces weight, on average, by somewhat more than 25% (eg, from 125 to 90 kg) up to 5 years after surgery. After 10 years, a weight loss of approximately 16% remains, on average slightly over 20 kg. This has substantial health and quality of life benefits for this patient group. The intervention, however, carries risks for complications.
- The scientific evidence for a wide range of alternative medicine methods is too weak to draw any conclusions concerning the possible effects which these methods have on obesity.
- The risks of obesity can be reduced.
The risks of obesity can be reduced through weight reduction, regardless of the methods used. Intervening against other risk factors – even when weight reduction does not succeed – can help reduce the risks of obesity. Such interventions would include increased physical activity, smoking cessation, and improved control of diabetes, high blood pressure, and elevated blood lipids.
- Limited information on cost effectiveness.
The cost to society for obesity and the complications of obesity are high. Information on the cost effectiveness of the various methods is, however, limited. The cost effectiveness of preventive methods cannot be calculated due to the uncertainty surrounding their effects. In treating obesity, the costs are relatively low for the weight reduction that is achieved through dietary counseling, behavioral therapy, dietary replacement formulas with low energy content, and surgery, but substantially higher for pharmacological treatment. No studies were found that estimated cost effectiveness based on an observed reduction in morbidity or mortality, or an improvement in the quality of life.
- Prejudice against obesity must be opposed.
Those affected by obesity should not be treated with disrespect and prejudice - many people risk becoming obese, but no one desires it. The reduced quality of life that individuals with obesity experience is partly attributed to the attitudes of people around them. Increased understanding for the origins of obesity and how difficult it is to treat may help reduce the prejudice against obese individuals, which occurs both within the health services and in society at large.