What Happens During Weight Loss Surgery

Exactly what your surgeon will do when you get weight loss surgery depends on what type of surgery you're getting. Weight loss surgery works in three basic ways:

  • Restricting how much food your stomach can hold at any time. This is "restrictive" weight loss surgery.
  • Preventing your digestive system from absorbing all the nutrition in the food you eat. This is "malabsorptive" surgery.
  • A combination of these two ways

Here's what each procedure involves.

Restrictive Weight Loss Surgery

Restrictive types of weight loss surgery are gastric banding, intragastric balloon, and vertical sleeve gastrectomy.

These procedures make less room in the stomach for food right after it's swallowed.

Gastric banding involves placing a band around the top end of the stomach to create a small pouch to hold food. The band limits the amount of food you can eat by making you feel full after eating small amounts of food.There are two approved gastric banding devices and procedures approved in the U.S. -- LAP-BAND and the Realize band.

The intragastric balloon is a saline-filled silicone balloon that is placed in the stomach, limiting the amount of food you can eat and making you feel full faster.

Vertical sleeve gastrectomy involves removing about 75% of the stomach. What remains of the stomach is a narrow tube or sleeve, which connects to the intestines.

Malabsorptive Weight Loss Surgery: Gastric Bypass and Biliopancreatic Bypass

Gastric bypass surgery also involves creating a small pouch. The difference between gastric bypass and gastric banding is that food doesn't pass through the pouch to be further digested in the larger part of the stomach.

Instead, the pouch empties directly into the small intestine. To make this work, the small intestine is severed. The surgeon connects one end of it to an opening in the new stomach pouch.

After this surgery, when you eat, food bypasses most of your stomach and the first part of your small intestines. That makes this surgery both restrictive and malabsorptive.

Surgeons rarely do weight loss surgery that's only malabsorptive. One exception is a surgery that removes much of the stomach. That surgery is called a biliopancreatic diversion with a duodenal switch.

Deciding on Weight Loss Surgery

Before you have weight loss surgery, you'll go through an evaluation process that includes counseling and various tests.

All types of weight loss surgery have pros and cons. Those that involve more cutting, sewing, and rearranging things inside of you may yield slightly better results, but they also may come with more side effects.

WebMD Medical Reference Reviewed by Minesh Khatri, MD on July 28, 2021


News release, Allergan.
American Society for Metabolic and Bariatric Surgery: "Bariatric Surgery."
Kelvin D. Higa, MD, program director of minimally invasive and bariatric surgery, Fresno Heart & Surgical Hospital, Fresno, CA; past president, American Society for Metabolic and Bariatric Surgery.
Walter Pories, MD, professor, founding chair of surgery department, Brody School of Medicine at East Carolina University, Greenville, NC.
Buchwald, H. The Journal of the American Medical Association, Oct. 13, 2004.
Sjöström, L. New England Journal of Medicine, Dec. 23, 2004.
Colquitt, J. Cochrane Database of Systematic Reviews, 2009.
Brolin, R. The Journal of the American Medical Association, Dec. 11, 2002.
Buchwald, H. Surgery, October 2007.
McMahon, M. Mayo Clinic Proceedings, October 2006.

© 2021 WebMD, LLC. All rights reserved.

Get Diet and Fitness Tips In Your Inbox

Eat better and exercise smarter. Sign up for the Food & Fitness newsletter.

By clicking Subscribe, I agree to the WebMD Terms & Conditions & Privacy Policy and understand that I may opt out of WebMD subscriptions at any time.