The primary impact of the Biliopancreatic Diversion (BPD) surgery is its restriction of nutrient absorption in a significant manner. Its impacts, both restriction of food intake and slowing down of the fat absorption, are the basis of weight loss. In the operation, 75-85% of the stomach volume is taken off (stomach tube). The remaining volume of the stomach is 200-500 cc. This volume, which is quite high compared to Gastric Bypass, does not reduce the life quality in the point of ingesting, contrary to Gastric Bypass. The major impact of the operation appears through the restriction of nutrient absorption. In Biliopancreatic Diversion (BPD) surgery, the stomach nerves and the pyrolic valve is preserved.