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

The two purely restrictive types of weight loss surgery are called gastric banding and vertical sleeve gastrectomy.

Both operations make less room in the stomach for food right after it's swallowed.

The surgeon uses a small part of your stomach to make a pouch at the end of your esophagus (the tube connecting your mouth to your stomach). This pouch holds only about half an ounce -- roughly the space in a shot glass. It fills up quickly and empties slowly, through a narrow opening to the larger part of the stomach.

Gastric banding involves placing a band around the top end of the stomach. There are two approved gastric banding devices and procedures approved in the U.S. -- LAP-BAND and the Realize band.

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 26, 2017


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