Dr. Ann O'Connor, MD

By far the most common of the gastric bypass surgeries is called Roux-en-Y. During this surgery, part of the stomach and small intestine are detached from the gastrointestinal tract, in order to make the tract smaller. The surgeon divides the stomach into two parts. The working stomach, at the end of the esophagus, is now tiny - only the size of a walnut. This makes patients feel full after eating a small amount of food. Then the small intestine is also divided, and after bypassing a section of the small intestine to reduce food absorption, the intestine is attached to the small stomach pouch. The patient now has a working stomach and intestine like before, only much smaller.

Because gastric bypass is used to treat extreme obesity, it can reduce the risk of some of the problems associated with obesity. Gastric bypass can help treat or reduce the risk for such conditions as heart disease, high blood pressure, sleep apnea, and type 2 diabetes. However, it is a major surgery and also carries risks itself. Any surgery can lead to infection, bleeding, or blood clots, and weight loss surgery in particular carries risks of leaks in the gastrointestinal system, malnutrition, bowel obstructions, and vomiting.

Typically patients are considered candidates for gastric bypass surgery if they have a BMI greater than 40, or sometimes if they have a BMI between 35 and 40 but are suffering from obesity-related illnesses such as diabetes. The outlook is generally good, with most patients losing between 50-75% of their excess weight in 1-2 years. However, patients must follow strict diet guidelines so that the stomach can heal, starting with no food at all, then followed by a liquid diet for some time. For many severely obese patients who have tried strict diets before without success, gastric bypass surgery is the tool that allows them to finally achieve their weight loss and health goals.