The gastric bypass procedure has been known for more than thirty years and consists of creation of a pouch from the upper stomach, from which food outflows directly to the small intestine. The treatment combines actions of reducing consumption and absorption. The stomach is divided into two parts with surgical staples. The loop of the small intestine (digestive loop) through which food is moved down is hooked up to the upper part of the stomach which is of capacity of approximately 30 ml. From the further part of the stomach, which may have been resected in some cases, digestive fluids stream down through the duodenum and then the small intestine (enzymatic loop). Both sections of the small intestine join together. Digestion takes place in this common loop (digestive loop). The length of specific sections of the intestine (particularly of the common section) and capacity of the smaller part of the stomach are determined in accordance with common standards.