How Does Gastric Bypass Work?

Decreasing Stomach Size

Gastric bypass is a serious abdominal surgery that is performed on patients who have a body mass index of at least 40. If a person has a BMI of 35 to 39, but has a serious health problem that is being caused by the obesity, that patient is also a candidate for the surgery. Gastric bypass works by surgically sealing off most of the patient's stomach. This creates a much smaller stomach that can hold less and will hold the food for a shorter time than if the entire stomach was being used.

Bypassing Part of the Intestines

To seal off the largest area of the stomach, the doctor will use miniature instruments to staple the stomach to close it off. Then, the doctor will bypass part of the patient's small intestine by connecting a lower portion of the small intestine directly to the stomach. By bypassing part of the small intestine, fewer calories from the patient's food will be absorbed by the intestines. Between the smaller stomach and the bypass of part of the intestines, the patient will be unable to take in a high number of calories and many of the calories eaten will not be absorbed by the body.

After the Surgery

With a smaller stomach, the patient can eat very small portions of food and not feel hungry. Patients have to go on special diets after the surgery to make sure that they get the nutrients they need. Because of the small number of calories that the patient can take in, every bite of food counts after having gastric bypass surgery. The patient will also have to take a few nutritional supplements to avoid the anemia and vitamin deficiencies that can occur as a result of fewer nutrients being absorbed by the intestines. While the surgery has a success rate as high as 75 percent, it is possible for patients to slowly stretch their stomachs to a larger size and to gain back the lost weight.