Gastric bypass – is the combined surgery procedure, during which both the size of the stomach (by almost 90%) and the length of the digestive tract is reduced. From the upper part of the stomach a small stomach pouch of 15-30 ml volume is created. Thanks to this, a very little amount of food is enough to experience the fullness. Usually, from the stomach the food passes to the small intestine, in which the biggest amount of nutrients and calories are being absorbed. During the gastric bypass surgery the created small stomach pouch is attached to the middle part of the small intestine (duodenum), in such a way the remaining part of the stomach and some part of the small intestine are bypassed. Such procedure shortens the movement of food through the digestive tract, therefore fewer nutrients and calories in foods are absorbed. The length of the bowels to be shortened depends on the patient‘s BMI. Patient must have 35 BMI or higher to qualify for this surgery.