A prospective randomized study of patients undergoing Roux-en-Y gastric bypass will be randomized in 2 groups: those following an Enhanced Recovery After Surgery (ERAS) program and those ones following a standard protocol. The ERAS program implies early liquids oral intake, early deambulation and multimodal analgesia (port sites infiltration with Bupivacain 0.5% associated with intravenous analgesia).