Gastric bypass surgery is used to treat severe obesity when techniques such as dietary changes, exercise and other methods have failed to control a patient’s weight. It is the most popular form of weight loss surgery (bariatric surgery) performed in the United States.

This type of surgery typically is performed on patients with a body mass index (BMI) of 40 or more. This measure is a calculation of a person’s height and weight, and a BMI of 40 represents a man who is about 100 pounds overweight, or a woman who is about 80 pounds overweight.

During a gastric bypass procedure, a patient’s digestive anatomy is surgically altered to restrict the amount of food they are physically able to eat at one time. In addition, the digestive tract is altered so that food bypasses part of the stomach and part of the small intestine, resulting in fewer calories being absorbed by the body.

Gastric bypass surgery is performed using general anesthesia, which means the patient is asleep during the procedure and does not feel pain. Gastric bypass can be performed as either traditional open surgery or as less invasive laparoscopy. The latter technique requires smaller incisions and generally has a shorter recovery time than the traditional technique.

Following surgery, patients are placed on a special diet that lasts for several months and progresses from liquids to pureed foods and soft foods. Eventually the patient will be allowed to eat solid foods. However, the changes to the digestive system brought on by surgery result in permanent restrictions on how much patients are able to eat and what kinds of food they can eat.