Previous chapters and many separate publications (1-4) have shown that conventional as well as pharmacological treatment of obesity is associated with poor longterm results. Recent publications from the intervention study Swedish Obese Subjects (SOS) have shown that conventional treatment results are particularly poor in settings not specialized in the treatment of overweight and obesity (5-8). Drug treatment of obesity results in 8-10% weight loss under conditions when placebo gives 4-6% weight loss (9). Although this is encouraging, much more efficient drugs are needed in the future. All these circumstances have constituted incentives for surgeons to develop techniques resulting in malabsorptive or restrictive effects on food intake. Several techniques achieve weight loss through both of these mechanisms and most likely also by changing the gastrointestinal signaling systems by which energy expenditure and/or appetite regulation may be modulated.