Weight-loss surgery helps you lose weight and lowers your risk of medical problems associated with obesity. Weight-loss surgery also is called bariatric surgery. Bariatric surgery helps with weight loss in two main ways:

• Restriction. Surgery is used to physically limit the amount of food the stomach can hold, which limits the number of calories you can eat.
• Malabsorption. Surgery is used to shorten or bypass part of the small intestine, which reduces the amount of calories and nutrients the body absorbs.

Some common types of weight-loss surgery are:

• Roux-en-Y gastric bypass
• Sleeve gastrectomy

In Roux-en-Y gastric bypass, the surgeon creates a small pouch at the top of the stomach. The pouch is the only part of the stomach that receives food. This greatly limits the amount that you can comfortably eat and drink at one time.

The small intestine is then cut a short distance below the main stomach and connected to the new pouch. Food flows directly from the pouch into this part of the intestine. The main part of the stomach, however, continues to make digestive juices. The portion of the intestine still attached to the main stomach is reattached farther down. This allows the digestive juices to flow to the small intestine. Because food now bypasses a portion of the small intestine, fewer nutrients and calories are absorbed.

In a sleeve gastrectomy, part of the stomach is separated and removed from the body. The remaining section of the stomach is formed into a tubelike structure. This smaller stomach cannot hold as much food. It also produces less of the appetite-regulating hormone ghrelin, which may lessen your desire to eat. However, sleeve gastrectomy does not affect the absorption of calories and nutrients in the intestines.