Gastric bypass weight loss surgery makes the stomach smaller and causes food to bypass the majority of the stomach and first part of the small intestine. Patients feel full more quickly* than when the stomach was its original size. This reduces the amount of food you can eat at one time.
In normal digestion, food passes through the stomach and enters the small intestine, where most of the nutrients and calories are absorbed. It then passes into the large intestine (colon), and the remaining waste is eventually excreted.
In gastric bypass, only a small part on the top of the stomach is used to create a new stomach pouch, roughly the size of an egg. The smaller stomach is then connected directly to the middle portion of the small intestine (jejunum), bypassing the rest of the stomach and the upper portion of the small intestine (duodenum). The procedure results in reduced calorie and nutrition absorption*.