Roux-en-Y is the most widely performed surgical procedure for weight loss. Gastric Bypass works in two ways. By restricting large amounts of food and the malabsorption of nutrients, patients simply can't eat as much as they did before surgery, because this small pouch can only accommodate a few ounces of food at a time and they subsequently lose weight. Additionally, because most of the stomach and some of the small intestine has been bypassed, some of the nutrients and calories in your foods will not be absorbed. 

A small thumb-sized pouch is created at the top of the stomach.. The remainder of the stomach is not removed, but is completely divided from the stomach pouch. The small intestine is divided and rearranged to provide an outlet to the small stomach, while maintaining the flow of digestive juices at the same time. Food enters the second part of the small intestine within about 10 minutes of beginning the meal.

Stomach before Surgery	Stomach after Surgery

Your anatomy is changed significantly by gastric bypass and thus requires a very careful dietary plan. Food will not go into the lower part of your stomach or the first portion of your small intestine, but both will still contribute enzymes for digestion in the lower intestines. Because the pouch restricts what you can eat, overeating can cause pain, nausea, and vomiting. In addition, foods that are high in sugar can dump into the intestines and cause severe nausea and diarrhea. Alcohol similarly can be absorbed quickly and can cause toxicity at surprisingly low levels. A gastric bypass always results in decreased absorption of certain vitamins and minerals. Thus all bypass patients require lifetime vitamin and calcium supplements.

Laparoscopic Procedure Specially designed instruments are inserted through small incisions. Surgical video cameras called laparoscopes are also inserted so the surgeon can see inside the body. Surgeons watch on monitors as they perform the surgery.
Open Incision Procedure This procedure involves a major incision from the breast-bone to the belly-button.