Gastric bypass and other weight-loss surgeries — known collectively as bariatric surgery — involve making changes to your digestive system to help you lose weight. Bariatric surgery is done when diet and exercise haven't worked or when you have serious health problems because of your weight. Some procedures limit how much you can eat. Other procedures work by reducing the body's ability to absorb nutrients. Some procedures do both.

While bariatric surgery can offer many benefits, all forms of weight-loss surgery are major procedures that can pose serious risks and side effects. Also, you must make permanent healthy changes to your diet and get regular exercise to help ensure the long-term success of bariatric surgery.

Types of bariatric surgery

Each type of bariatric surgery has pros and cons. Be sure to talk to your doctor about them. Here's a look at common types of bariatric surgery :

• Roux-en-Y gastric bypass : This procedure is the most common method of gastric bypass. This surgery is typically not reversible. It works by decreasing the amount of food you can eat at one sitting and reducing absorption of nutrients. The surgeon cuts across the top of your stomach, sealing it off from the rest of your stomach. The resulting pouch is about the size of a walnut and can hold only about an ounce of food. Normally, your stomach can hold about 3 pints of food. Then, the surgeon cuts the small intestine and sews part of it directly onto the pouch. Food then goes into this small pouch of stomach and then directly into the small intestine sewn to it. Food bypasses most of your stomach and the first section of your small intestine, and instead enters directly into the middle part of your small intestine.
• Sleeve gastrectomy : With sleeve gastrectomy, about 80% of the stomach is removed, leaving a long, tube-like pouch. This smaller stomach can't hold as much food. It also produces less of the appetite-regulating hormone ghrelin, which may lessen your desire to eat. Advantages to this procedure include significant weight loss and no rerouting of the intestines. Sleeve gastrectomy also requires a shorter hospital stay than most other procedures.
• Biliopancreatic diversion with duodenal switch : This is a two-part surgery in which the first step involves performing a procedure similar to a sleeve gastrectomy. The second surgery involves connecting the end portion of the intestine to the duodenum near the stomach (duodenal switch and biliopancreatic diversion), bypassing the majority of the intestine. This surgery both limits how much you can eat and reduces the absorption of nutrients. While it is extremely effective, it has greater risk, including malnutrition and vitamin deficiencies.