Roux-en-Y gastric bypass surgery uses a combination of restriction and malabsorption.
During this procedure, the surgeon creates a small isolated stomach pouch by stapling. The surgeon then attaches a Y-shaped section of the small intestine directly to this small pouch. The smaller stomach pouch causes patients to feel full sooner and eat less; the bypass of a portion of the small intestine means the patient's body will absorb fewer calories. In addition, after gastric bypass, most patients will no longer tolerate sweet foods and beverages because of a reaction called dumping syndrome.
Gastric bypass can be done through small incisions (the minimally invasive approach, also known as laparoscopic surgery), or as an open procedure through an upper abdominal incision.