The weight loss surgical procedures in use today range from gastric banding to open biliopancreatic diversion. Bariatric procedures are classified according to their mechanism of action: restrictive, malabsorptive, or a combination of restrictive and malabsorptive. In this lecture, Philip Schauer, MD, FACS, analyses all aspects of these techniques presenting the results of these procedures in terms of weight loss, conversions rate, postoperative complications, in-hospital stay.