BPD is quite complex and involves reducing the size of the stomach and rerouting the intestines. About 50% of the distal stomach is removed. The small bowel is divided, creating a double intestinal tube. In essence, in one passes the food, and in the other one, the digestive juices and the mix of the two happens far from the usual location. The mechanism of action of BPD is the reduced absorption of foods, particularly of fats and carbohydrates. BPD offers good weight loss and long-term weight maintenance, and powerful action against type 2 diabetes and hypercholesterolemia. However, malabsorption also entails: frequent bowel movements with soft and foul-smelling stools and flatulence lifelong need to take vitamin supplements, calcium and iron need of a protein-rich diet (meat, fish, eggs, sausages, cheeses) eventual diseases (anaemia, osteoporosis, protein malnutrition). For these reasons, BPD is rarely performed and only in very selected cases. Dr. Marinari has worked for 20 years with the inventor of this method and knows very well its advantages and disadvantages. The DS is a procedure very similar to BPD and is always revisional. Since stomach resection is the same as Sleeve Gastrectomy, DS is one of the options available if, after Sleeve Gastrectomy the patient had regained weight. In comparison with BPD, in the DS the pylorus is maintained. In essence, the pylorus is a valve that regulates the exit of food and drinks from the stomach, and its maintenance reduces to a certain extent the side effects of BPD. However, in the long run, the advantages and disadvantages of DS remain very similar to those of BPD.