first appeared in 1980, biliopancreatic diversion involves two parts: gastrectomy and intestinal bypass. firstly, gastrectomy removes a large portion of the stomach. reduction in stomach capacity decreases the appetite of patients. secondly, intestinal bypass anastomoses the proximal duodenum and the distal ileum. this intestinal bypass is different from the above three bypasses in the way that the blind loop carrying bile and digestive enzymes will drain into the distal portion of the small intestine. with this technique, the absorption of nutrients, in particular, fat, can be reduced tremendously.