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What Is Gastric Bypass Surgery?

WebMD Medical Reference
Reviewed by Andrew Seibert, MD

Roux-en-Y gastric bypass surgery is the most commonly performed gastric bypass surgery surgery today, accounting for about 80% of all weight loss surgeries in the U.S. The procedure has two parts:

Part One: Creation of a Small Pouch

During this part of the surgery, the stomach is divided in two -- a large portion, and a much smaller one. Then, in a process sometimes called "stomach stapling,” the small part of the stomach is sewn or stapled together to make a pouch, which can hold only a cup or so of food.

With such a small stomach, people feel full quickly and eat less. This strategy is also called "restrictive," since the new stomach size restricts food intake.

Part Two: Bypass

The new, small stomach pouch is disconnected from the first part of the small intestine (the duodenum), and then connected to a portion of the small intestine slightly farther down (the jejunum). This surgical technique is called a "Roux-en-Y."

After a Roux-en-Y, food passes directly from the stomach into the jejunum, bypassing the duodenum. This leads to reduced absorption of calories and nutrients. This weight loss method is called "malabsorptive."

Stomach stapling and Roux-en-Y are typically performed during the same surgery and together are called a "Roux-en-Y gastric bypass." Usually, both are done laparoscopically (using tools inserted through small incisions in the belly). When laparoscopy isn’t possible, a laparotomy (involving a large incision in the middle of the belly) may be used

Recovery and Potential Complications

After gastric bypass surgery, people typically stay in the hospital for 2 to 3 days and return to normal activity within 2 to 3 weeks. Nearly 10% of people have complications, which are usually minor and include:

  • Wound infections
  • Digestive problems
  • Ulcers
  • Bleeding

Nearly 1% to 5% of people have serious or life-threatening complications, such as:

The risk of complications is lower at centers that perform more than 100 weight loss surgeries per year. Deaths in the month following gastric bypass surgery are rare (about 0.2% to 0.5%, or less than one in 200 people) when the procedure is performed by a highly experienced surgeon.

Other health problems can also occur as a result of the surgery. For example, the decrease in the absorption of nutrients like iron and calcium can cause anemia and osteoporosis. But taking nutritional supplements and getting blood tests can reduce this risk.

What to Expect After Gastric Bypass

Post-surgery weight loss is often dramatic. On average, patients lose 60% of their extra weight. For example, a 350-pound person who is 200 pounds overweight would drop about 120 pounds.

Many weight-related health problems improve or even disappear after gastric bypass surgery. The most common are diabetes, high blood pressure, asthma, and obstructive sleep apnea.

However, losing weight and maintaining the loss require ongoing lifestyle changes. Adapting to eating several small meals a day and regular exercise are important to keep weight off.

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