Gastric bypass surgery, a type of bariatric surgery (weight loss surgery), is a surgical procedure that alters the process of digestion. Bariatric surgery is the only option today that effectively treats morbid obesity in people for whom more conservative measures such as diet, exercise, and medication have failed.

There are several types of gastric bypass procedures, but all of them involve bypassing part of the stomach and small bowel by greater or lesser degrees. For this reason, procedures of this type are referred to as malabsorptive procedures, because they involve bypassing a portion of the small intestine that absorbs nutrients.

These procedures also involve creating a small pouch of the stomach that serves as the “new” stomach or surgically removing part of the stomach. Gastrointestinal staples facilitate these operations, but these are not the same as stomach stapling. Stomach stapling was one of the first techniques tried in the development of bariatric surgery, but it not effective.

Although a gastric bypass procedure is malabsorptive, it is also restrictive because the size of the stomach is reduced so that the amount of food you can eat is “restricted” due to the smaller stomach. While malabsorptive procedures are more effective in causing excess weight to be lost than procedures that are solely restrictive, they also carry more risk for nutritional deficiencies.