There is more to gastric bypass than merely controlling stomach size. During gastric bypass surgery, a large portion of the patients stomach is stapled together, leaving a tiny pouch. When you get your gastric bypass surgery you will have a new stomach that only holds about three tablespoons of food at a time. With your stomach pouch reduced to the size of a walnut, you'll need to follow a gastric bypass diet. The surgeon does not remove any part of the stomach or other tissue while doing the gastric bypass operation. This operation is the most common gastric bypass procedure performed. In another more complicated gastric bypass operation, portions of the stomach are removed. In this more complicated gastric bypass operation, portions of the stomach are removed. This is a relatively complex operation. It is recommended against having it reversed. Results from long-term follow-up data of gastric bypass surgery show that over a five-year period, patients lost 58% of their excess weight. Eating sweet or sugary foods promotes "dumping," a reaction which can occur after the gastric bypass operation. Dumping syndrome occurs when the small intestine fills too quickly with undigested food from the stomach, as can happen following gastric bypass surgery. Other commonly seen complications of gastric bypass surgery include intolerance to some foods, vitamin and mineral deficiency, gallstones, bleeding stomach ulcers, hernia and dehydration. The most important of all, given that gastric bypass patients have a new, tiny stomach to fill is diet. Another recent problem which is fairly common, especially in menstruating women, after gastric bypass, is anemia. Because many nutrients are not absorbed by the body after gastric bypass, anemia can be a long-term effect. Due to the changes in digestion after gastric bypass surgery, patients may develop such nutritional deficiencies as anemia, osteoporosis, and metabolic bone disease. The gastric bypass operation reduces the progression and mortality of non-insulin-dependent diabetes mellitus. However, this complication only occurs to a very small degree in the gastric bypass operation. One of biggest advancements in the gastric bypass operation has been the technique used to enter into the abdomen through the laparoscopic approach. Gastric bypass surgery creates dramatic changes in the size and shape of the stomach. Barely 16 months after gastric bypass surgery, which reduced your stomach to the size of a hard-boiled egg, a patient is able to shed 185 pounds.