While global prevalence of obesity continues to increase dramatically, treatment options remain less than optimal. The etiology of obesity is multifactorial, ranging from lifestyle choices such as excess food intake and insufficient physical activity, to use of medications that have weight gain as an undesirable side effect. Economic and political determinants of available foodstuffs and even social networks may also contribute to obesity. Successful management of obesity requires the understanding and acceptance of a new paradigm that identifies obesity as a disease--one defined by waist circumference--that requires treatment. Obesity meets all accepted criteria of a medical disease, including a known etiology, recognized signs and symptoms, and a range of structural and functional changes that culminate in pathologic consequences. Excess adipose tissue acts as an endocrine organ to produce excess free fatty acids, as well as tumor necrosis factor-alpha, interleukin-6, leptin, and plasminogen activator inhibitor-1. These bioactive molecules are associated with hyperinsulinemia, hyperglycemia, insulin resistance, development of diabetes, endothelial damage, and the onset and progression of atherosclerotic lesions. Options for treating obesity include lifestyle modifications (dietary changes, increased physical activity, behavior modification) and, for the morbidly obese, surgery. Lifestyle modification is rarely successful over the long term; therefore, addition of pharmacotherapy should be considered for obese individuals who have difficulty achieving and maintaining weight goals with lifestyle modifications alone. Several weight loss drugs are available for long-term use, with others in various stages of clinical development.