the intestinal bypass surgery, as the name suggests, anastomoses 14 inches of the proximal duodenum, the part of the small intestine closest to the stomach, to the 4 inches of the distal ileum, the part of the small intestine closest to large intestines. this creates a blind loop and bypasses nearly 85-90 % of the small intestine. as a corollary, the absorption of nutrients is greatly reduced, and thus lead to apparent weight reduction.