About 75 percent of the stomach is removed. This restricts the amount of food a person can eat at one time. The outlet valve (pylorus) between the stomach and small intestine is left intact. The small intestine is rearranged so food from the stomach enters further down. With less exposure to digestive juices, your body retains less fat and calories from the food you eat. To maintain their health, patients need a high-protein diet, and lifelong vitamin and mineral supplements.
Read more about the duodenal switch procedure (sometimes also known as gastric bypass or malabsorptive surgery).