Bariatric surgery, is performed only on severely overweight people who are more than twice their ideal weight. This level of obesity often is referred to as morbid obesity since it can result in many serious, and potentially deadly, health problems. This surgery is performed on people whose risk of complications of surgery is outweighed by the need to lose weight to prevent health complications, and for whom supervised weight-loss and exercise programs have repeatedly failed. Most people lose about 60% of their excess weight through this treatment. Changes in diet and exercise still are required to maintain a normal weight. With obesity surgery the volume of food the stomach can hold is reduced from about four cups to about 1/2 cup.
In gastric bypass surgery the volume of the stomach is reduced, and its main body is separated from a newly created pouch which is attached at one end to the esophagus and at the other end opens into the small intestine. Food flows through this pouch, bypassing the main portion of the stomach and emptying slowly into the small intestine. In vertical banding gastroplasty an artificial pouch is created and plastic mesh is sutured into part of the pouch to prevent it from dilating. The food enters the small intestine farther along that it would enter if exiting the stomach normally. This reduces the time available for absorption of nutrients. Jejunoileal bypass involves shortening the small intestine, but because of the high occurrence of complications it has largely been abandoned for the other, safer procedures.
Pre-surgery counseling including dietitian’s counselling is done to help patients anticipate what to expect after the operation. After the operation, most patients are restricted to a liquid diet for 2–3 weeks. Patients then move on to a diet of pureed food or a week or two and, after about 4-6 weeks, most can tolerate solid food. High fat food is restricted because it is hard to digest and causes diarrhea. Patients are expected to work on changing their eating and exercise habits to assist in weight loss. Most people eat some small meals a day once they return to solid food. Eating too quickly or too much after obesity surgery can cause nausea and vomiting as well as intestinal “dumping,” a condition in which undigested food is shunted too quickly into the small intestine, causing pain, diarrhea, weakness, and dizziness.