induction of malabsorption is the most prominent effect of the surgery. the small intestines are responsible for most of the absorption of nutrients. by bypassing a considerable length of the small intestines, this type of surgery greatly reduces the absorption capacity of the digestive system. malabsorption is especially prominent in biliopancreatic diversion. not only does it reduce the length of the small intestine for absorption, but it also drains the bile and digestive enzymes only to the distal ileum. bile is essential for fat absorption, while digestive enzymes facilitate the intake of proteins. draining them to only the distal ileum further reduces the efficiency of intestinal absorption, hence achieving the goal of weight reduction.