The prevalence of obesity is growing at an alarming rate. Thus, investigation into the etiology, comorbidities, and treatment of obesity has burgeoned in recent years. While novel therapies--both behavioral and pharmacological--have been developed and tested, the mean weight losses achieved with nonsurgical approaches have remained virtually unchanged over the past 20 years. Fortunately, the modest weight losses achieved with these methods are associated with significant reductions in obesity-related health problems. With the most intensive available treatment (i.e., bariatric surgery), many patients achieve remission of comorbid conditions. This article defines obesity and provides an overview of the disease conditions associated with excess weight. Treatment options and outcomes are reviewed and future steps-including efforts to prevent obesity--are identified. Finally, the literature on the relationship between obesity and depression is examined.