If a patient requires even greater weight loss than banding techniques produce, a gastric bypass operation is considered. Gastric bypass procedures reduce absorption of food, in addition to restricting food intake. Patients who have bypass operations generally lose 70 percent of their excess weight within one and a half years.
In Roux-en-Y gastric bypass, the most common bariatric procedure, a small stomach pouch is created by stapling to separate it from the rest of the stomach. Then, a section of the small intestine is attached to the new pouch to allow food to bypass the first portion of the small intestine to reduce calorie and nutrient absorption. The limited quantity of food, combined with reduced absorption of calories, results in faster and perhaps more pronounced weight loss than is normally achieved by the gastric banding procedure.
This procedure usually requires a two- to three-day hospital stay, and normal activities can be resumed in four to five weeks. Patients with type 2 diabetes often see immediate improvement in their diabetes after this surgery.