Adults with a body mass index (BMI=kg/m²) of 25-<30 are considered overweight; those with a BMI of ≥30 are considered obese.

Resveratrol is a phytochemical found in the skin of red grapes and in many other plants, including berries, plums and peanuts. As a constituent of red wine, it has been associated with cardioprotective effects. Dietary supplements containing resveratrol are now being widely promoted as antioxidants that can prevent agerelated diseases.

A recent article in the New England Journal of Medicine confirms something that others, including The Medical Letter (Treat Guidel Med Lett 2008; 6:23), have been saying for years: no particular combination of protein, carbohydrate and fat in the diet offers any advantage in losing weight. This randomized 2-year trial followed 800 overweight and obese subjects on low fat/average protein, low fat/high protein, high fat/average protein, and high fat/high protein diets. Carbohydrate intake varied from 35% (in the high fat/high protein diet) to 65% (in the low fat/average protein diet). All patients were advised to undertake 90 minutes of moderate exercise per week and given a “caloric prescription” to produce a deficit of 750 kcal per day. Most participants lost weight in the first 6 months and regained some thereafter. There was no significant difference in weight loss between different diets and no indication that any particular diet was more pleasant or less painful than any other. Average weight loss at the end of the trial was 4 kg among the remarkably high 80% of subjects who completed the trial, and 9 kg among those who also attended two thirds of the counseling sessions offered to the participants (FM Sacks et al, N Engl J Med 2009; 360:859).

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Losing even a small amount of weight and increasing physical activity can prevent some of the complications of obesity, particularly type 2 diabetes. Diet and exercise are the preferred methods for losing weight but are associated with high long-term failure rates. Drugs may help some patients, but all currently available drugs for weight reduction have drawbacks. Gastric surgery can produce marked weight loss in the severely obese, but long-term data on safety are limited.

The US Department of Health and Human Services, in conjunction with the US Department of Agriculture, has released the latest update of its Dietary Guidelines (www.health.gov). The emphasis this time is on weight loss through calorie restriction and exercise. A low-fat intake is recommended; a low-carbohydrate diet is not. Fruits, vegetables and whole grains are encouraged. A review of Diet, Drugs and Surgery for Weight Loss appeared in the December 2003 issue of Treatment Guidelines from The Medical Letter.

The latest definitions of overweight and obesity are based on body mass index (BMI). The BMI is calculated by dividing the weight in kilograms by the square of the height in meters (kg/m²). More than half of American adults are considered overweight with a BMI of ≥25, and about one third are obese with a BMI of ≥30. All ages seem to be affected; the proportion of children and adolescents who are overweight has more than doubled in the past 25 years. There is no lack of effort to treat obesity: drugs, diets and programs to change lifestyle are the basis for a large and flourishing industry. The frequent failure of diet and drug treatment sometimes leads to recommendations for surgery, usually restricted to those with a BMI ≥40.

Liquid diets for weight reduction, once discredited because of their adverse effects, are becoming popular again. Now, formula diets are available through physicians or hospitals as part of a packaged weight-reduction program that includes nutrition education and modification of eating and exercise habits. Three widely used programs are Optifast (Sandoz), Medifast (Nutrition Institute of Maryland, 1840 York Road, Timonium, MD 21093) and HMR (Health Management Resources, 59 Temple Place, Boston, MA 02111).