The American Medical Association Council on Scientific Affairs recently emphasized the importance of nutritionally sound weight reduction diets and changes in life-style to promote long-term weight control. The purpose of this study was to evaluate long-term effectiveness and to identify predictors of success of an intensive multidisciplinary program utilizing the time-calorie displacement diet, a low-fat, high-complex-carbohydrate diet, to promote and maintain reduced body weight. In 213 obese adults consecutively entering the program, including dropouts, weight loss averaged 6.3 kg (0.4 kg/week) and 16% of excess weight over 7 months of treatment. The 78 (37%) completing the recommended 15 visits lost a mean of 10.8 kg and 28% of their excess weight while under treatment. Weight loss was largely predicted by number of visits, which was more important than treatment duration. An increased number of visits was predicted by being married, being female, and reporting a usual diet low in snack foods. Of 147 patients contacted at posttreatment follow-up, 53% maintained their weight loss or continued to lose weight an average of 25 months later and 24% experienced weight rebound but were still below their pretreatment weight; only 23% regained their lost weight. Mean net weight loss from pretreatment to follow-up was 8.0 +/- 1.0 kg (mean +/- standard error of the mean). No factor significantly predicted posttreatment weight rebound. Results suggest that a nutritionally sound diet, prescribed in a multidisciplinary program and emphasizing life-style changes, can result in long-term weight control in a majority of patients treated.