Gastric bypass surgery involves the formation of a small stomach pouch to restrict food intake and the re-routing of the duodenum and other segments of the small intestine to cause malabsorption (decreased ability to absorb calories and nutrients from food). This technique produces more weight loss than restriction operations like gastric banding, which only decrease food intake. The diet after the surgery starts with a two week liquid-only diet, two weeks of semi-solid, pureed foods and then solids. People who have bypass surgery generally lose two-thirds of their excess weight within two years.
There are two types of gastric bypass procedures:
• Roux-en-Y gastric bypass (RGB): This procedure involves the creation of a smaller stomach pouch which limits the amount of food you can eat. A Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the duodenum as well as the first portion of the jejunum. This results in reduced calories and nutrient consumption. The procedure is performed laparoscopically and is the most common gastric bypass surgery.
• Extensive gastric bypass (biliopancreatic diversion): This is a more complicated gastric bypass procedure in which the lower portion of the stomach is removed. The small pouch that remains is connected directly to the final segment of the small intestine, thus completely bypassing both the duodenum and jejunum. It is not as widely used because of the high risk for nutritional deficiencies