Gastric sleeve is a relatively new standard method that complements the Roux-Y gastric bypass. The doctor removes three-quarters of the stomach during gastric sleeve surgery. After the procedure, the stomach has the shape of a tube. The reduced stomach volume causes the operated person to feel full even after small amounts of food, and the hunger hormone ghrelin is also reduced. This peptide (= amino acid molecule) stimulates the appetite; its level in the blood rises when you are hungry and falls after you eat.