Obesity is a chronic, complex, multifactorial disorder with increasing prevalence in modern society. Lifestyle modification has had limited success in treating this disorder. Currently approved pharmacologic treatments for obesity include sibutramine and orlistat, which have been associated with significantly greater weight loss than that seen with dieting alone. In addition, a greater percentage of patients who receive medical treatment achieve weight losses of more than 5% to 10% of their initial body weight. This weight loss is associated with improvements in blood pressure, insulin sensitivity, and dyslipidemia. Multiple new therapies that target several different regulatory pathways are currently in clinical trials.