If you undergo gastric bypass surgery, your stomach will be made smaller and your food intake will bypass part of the small intestine. Because of a smaller stomach, you will feel full more quickly thereby reducing the amount of food you eat and thus the calories consumed. Bypassing part of the intestine also results in less absorption of calories. The obvious final result of this surgery is that you lose weight.

The most familiar form of gastric bypass surgery is a Roux-en-Y gastric bypass. In a Roux-en-Y gastric bypass, a small pouch is made at the top of the stomach with the help of surgical staples or a plastic band. It reduces the size of the stomach, and the smaller stomach is connected directly to the middle portion of the small intestine, bypassing the rest of the stomach and the upper portion of the small intestine.

This procedure can be either open or laparoscopic. In the former, a large incision is made in the abdomen while the latter involves making a small incision and using small instruments and a camera to guide the surgical process. After surgery, most people can resume their normal activities within five weeks.

Normally gastric bypass surgery is considered when your BMI is 40 or more or you have a life-threatening or disabling condition related to obesity. Doctors may also consider the duration of obesity, history of alcohol abuse, psychiatric problems, and your age before deciding on a gastric bypass.

After gastric bypass surgery most people lose about one-third of their excess weight in one to four years. The risks involved in this surgery include an infection in the incision, a leak from the stomach into the abdominal cavity, and a blood clot in the lung. It may also lead to gallstones or nutritional deficiency.