Obesity is a serious, lifelong, worldwide health problem. Once obese, few people are able to lose their excess weight. Bariatric surgery is an intervention that has produced substantial and sustained weight loss in adults. It is offered increasingly as an option for extremely obese adolescents. Selection criteria have been proposed by several expert consensus panels. Outcomes and metabolic consequences of bariatric surgery on glucose-insulin interactions, diabetes, sleep architecture, the gastrointestinal tract, asthma, cardiovascular dysfunction, renal parameters, polycystic ovarian syndrome, bone health, nutrition, gynecologic concerns, and mental health are reviewed here.