Patient selection and the physiology of gastrointestinal antiobesity operations.

Antiobesity surgery largely is "behavioral surgery"--the results rely on behavioral factors more than on the technical performance of the procedure. Therefore, patient selection and pre- and postoperative patient education are critical for outcome. The operations rely on mechanical and biochemical mechanisms, such as: (1)limiting food consumption through restriction by activating satiety or nimiety; (2) increasing or decreasing appetitive gastrointestinal peptides; and (3) reducing substrate stores by way of malabsorption or increased thermogenesis to ensure weight loss. The balance between physiologic mechanisms that promote weight loss and motivational factors that cause maladaptive eating is the greatest challenge to effective surgical treatment of obesity.