Is a chronic condition that is difficult to treat through diet and exercise alone. Gastrointestinal surgery is 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 in other treatments for obesity, the best results are achieved with healthy eating behaviors and regular physical activity.

People who may consider gastrointestinal surgery include those with a body mass index (BMI) above 40-about 100 pounds of overweight for men and 80 pounds for women . 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.

The concept of gastrointestinal 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 passed along too fast for the body to absorb many calories. 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.

Gastrointestinal surgery for obesity, also called bariatric surgery, alters the digestive process. The operations promote weight loss by closing off parts of the stomach to make it smaller. Operations that only reduce stomach size are known as "restrictive operations" because they restrict the amount of food the stomach can hold.

Some operations combine stomach restriction with a partial bypass of the small intestine. These procedures create a direct connection from the stomach to the lower segment of the small intestine, literally bypassing portions of the digestive tract that absorb calories and nutrients. These are known as malabsorptive operations.

Five- to ten-million people in the United States are morbidly obese-defined as100 pounds or more overweight or having a Body Mass Index (BMI) of 40 or greater. Ninety-five percent of morbidly obese people who lose weight through traditional medically managed programs ultimately regain it.

People who are obese have higher rates of medical problems. If a person suffers from mild obesity then diet and exercise are usually the proper treatment. Once a person reaches the level of morbid obesity, the weight causes quicker and more extensive damage to the body. These factors translate into a greater need for weight loss, supporting the rationale for more extreme measures such as surgery to control weight.

The medical complications of obesity may occur in moderately obese people, but the frequency of these associated problems (such as heart disease, high blood pressure, diabetes, premature death, etc.) increases dramatically as weight increases. For example, very obese men between the ages of 25-35 have a 12 fold greater risk of dying prematurely compared to their normal weight counterparts.