In a gastric bypass procedure the stomach is divided with the help of a staple line into a small upper pouch at the end of the oesophagus and a larger remnant stomach. The bigger remnant stomach is circumvented and therefore has no more storing function. The small intestine is divided and re-arranged with the small pouch. The other end is reconnected with the small intestine about 150 cm further down. Due to this by-pass, food only comes into contact with the digestive juices consisting of pancreatic enzymes and bile in the lower parts of the intestine. Thus different metabolic systems are influenced in a positive way.