The increasing prevalence of overweight and obesity in adults and children demonstrates a steadily growing epidemic. This rising rate of obesity is associated with obesity related comorbidities including cardiovascular disease, hypertension, some cancers, joint disease, and particularly, type 2 diabetes. Modest weight loss (5% to 10% of total body weight) through lifestyle intervention approaches has been found to have a beneficial effect on comorbid conditions, particularly hypertension and type 2 diabetes. Effective behavioral treatment of obesity involves modification of eating and physical activity patterns to yield negative energy balance. Research studies have found that interventions that combine a low-calorie diet, increased physical activity, and behavior therapy are most effective for weight loss and maintenance. Furthermore, extended length of treatment contact, weight loss satisfaction, and social support may promote positive long-term outcomes in obese adults and children.