In patients with obesity, low-fat diets seem to result in a weight loss of 3-4 kg at 3 years, but long-term data are limited. Calorie-controlled diets seem to outperform low-fat diets with reported weight losses of 6-7 kg at 4 years, but, again, data are very limited; an initial very-low-calorie diet approach does not lead to greater weight loss than low-fat diets in the long term. Use of meal replacements can lead to an 8 kg weight loss at 4 years, but this finding has been reported only in one, uncontrolled study. High-protein, low-carbohydrate (or very-low-carbohydrate) diets have also been evaluated and seem to be superior to high-carbohydrate diets at least for up to 2 years. Very-low-carbohydrate diets can lead to elevations in LDL cholesterol levels in some individuals. Cognitive behavioral therapy added to diet therapy can facilitate approximately 5 kg additional weight loss, and exercise can facilitate an additional 1-1.5 kg weight loss. Drug treatment, particularly with sibutramine and rimonabant, can increase weight loss with a mildly hypocaloric diet by an additional 3-5 kg, but weight-loss drugs are costly and have adverse effects. If dietary and medical therapies fail, gastric banding can lead to a weight loss of ∼14% at 10 years, with greater losses of up to 25% with gastric bypass and gastroplasty. Bariatric surgery can also lead to a reduction in mortality and comorbidities but adverse effects can occur including nutritional deficiencies and gastrointestinal symptoms.