Gastric bypass surgery, a type of bariatric surgery (weight loss surgery), is a surgical procedure that alters the process of digestion. 

Roux-en-Y gastric bypass, the most commonly performed bariatric procedure, is both malabsorptive and restrictive. This surgery can result in two-thirds of excess weight loss within two years. The procedure involves reconstructing the stomach to create a small pouch that holds less food and then shaping a portion of the small intestine into a "Y". The "Y" portion of intestine is then connected to the stomach pouch so that when food is being digested it travels directly into the lower part of the small intestine, bypassing the first part of the small intestine (called the duodenum) and the first part of the second section of the small intestine (called the jejunum). The effect of bypassing these sections of the intestine is to restrict the amount of calories and nutrients that are absorbed into the body.

Please click on the picture below for an animation of gastric bypass surgery.

The Roux-en-Y gastric bypass may be performed with a laparoscope rather than through an open incision in some patients. This procedure uses several small incisions and three or more laparoscopes - small thin tubes with video cameras attached - to visualize the inside of the abdomen during the operation. The surgeon performs the surgery while looking at a TV monitor. A laparoscopic method allows the physician to make a series of much smaller incisions. Laparoscopic gastric bypass can sometimes reduce the length of hospital stay, the amount of scarring, and may result in a quicker recovery than an open procedure