In a gastric bypass, the upper part of the stomach is separated from the rest of the stomach to form a gastric pouch. The upper section of the small intestine is severed and one leg of it is connected to the gastric pouch.
The small intestine, which comes from the blindly closed stomach and contains the digestive juices from the duodenum, is sewn into this raised loop of small intestine. This bypasses the stomach. After gastric bypass surgery, the patient must avoid ingesting large and concentrated amounts of carbohydrates (sugar, starch products), as these can lead to dizziness attacks.
A consistent intake of vitamins and trace elements is necessary. The average reduction in excess weight is 50-60%.