Background: One third of Americans are obese, according to the 1988-1991 National Health and Nutrition End point Survey 111 survey. Obesity increases the risk of death and a variety of chronic diseases. Numerous commercial weight loss programs demonstrate short-term success. Objectives: To assess maintenance of weight loss achieved during dieting. Methods: We surveyed 192 participants in the Sandoz Nutrition (Sandoz Pharmaceuticals, Minneapolis, Minn) diet program approximately 3 years after participation. Initial data were supplied by the diet clinics and follow-up data, including weight at various points after the program, participation in other weight loss programs, and lifestyle variables, such as exercise, smoking, and television watching, were collected by a mailed questionnaire. Results: On average, the group lost 22 kg during the diet program. After the follow-up period, the mean weight (mean, 102.6 kg) was only modestly less than the group's original weight at the start of the diet (mean, 105.9 kg). Twelve percent of the subjects maintained 75% of their weight loss after leaving the diet program, 57% maintained at least 5% of the loss, and 40% gained back more than they had lost during the diet. The frequency of exercise after the diet program was the strongest predictor of weight loss maintenance, while television viewing predicted a gain in weight. Conclusion: Given the apparent lack of substantial, long-term success at weight reduction, perhaps greater emphasis should be placed on prevention of obesity.