The oldest and most popular bariatric surgery, Roux-En-Y gastric bypass works very well for patients who want to lose weight. With this approach, surgery is used to shrink the stomach into a small pouch and attach it to a piece of the small intestine. This procedure forces patients to eat less and limits the kind of food they can eat. Those who undergo this surgery lose an average of 65% of excess weight and over 80% of patients keep off at least 50% of initial excess weight lost. Eating better and exercising is very important after gastric bypass surgery.