One group of patients of the study will have done the simplified laparoscopic gastric bypass, with a vertical gastric pouch of about 20 ml, a 150 cm Roux-en-Y limb constructed in an antegastric antecolic fashion, and a biliary limb of 100 cm. Anastomosis will be done with endoscopic surgical linear stapler, closing the apertures with continuous absorbable running sutures. The Petersen space and the mesenteric defect will be closed with non-absorbable sutures.