Severe obesity is a chronic condition that is difficult to treat through diet and exercise alone. Weight loss surgery is sometimes the best option for people who are severely obese and cannot lose weight by traditional means or who suffer from serious obesity-related health problems. The surgery promotes weight loss by restricting food intake and, in some operations, interrupting the digestive process. As with other treatments for obesity, the best results are achieved with healthy eating habits and regular physical activity.

People who may consider weight loss surgery include those with a body mass index (BMI) above 40—about 100 pounds overweight. People with a BMI between 35 and 40 who suffer from type 2 diabetes or life-threatening cardiopulmonary problems, such as severe sleep apnea or obesity-related heart disease, may also be candidates for surgery. It is best for those considering surgery to check with their insurance company to find out what their guidelines are for approving coverage for surgery.

The concept of weight loss surgery to control obesity grew out of results of operations for cancer or severe ulcers that removed large portions of the stomach or small intestine. Because patients undergoing these procedures tended to lose weight after surgery, some physicians began to use such operations to treat severe obesity. The first operation that was widely used for severe obesity was the intestinal bypass. This operation, first used 40 years ago, produced weight loss by causing malabsorption. The idea was that patients could eat large amounts of food, which would be poorly digested or pass through the body too quickly for many calories to be absorbed. The problem with this surgery was that it caused a loss of essential nutrients and its side effects were unpredictable and sometimes fatal. The original form of the intestinal bypass operation is no longer used.