"Roux-en-Y" gastric bypass surgery -- where most of the stomach is bypassed and a small stomach pouch is made -- is the most commonly performed weight loss surgery today, accounting for about 80% of all weight loss surgery in the U.S.
As performed today, gastric bypass surgery has two parts:
Creation of a small stomach pouch
During this part of the surgery, the stomach is divided into a large portion, and a much smaller portion. The small part of the stomach is then sewn or stapled together to make a small pouch (this part is sometimes called "stomach stapling"). The small stomach pouch can only hold 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.
"Roux-en-Y" creation (bypass)
In this part of the surgery, the new, small stomach pouch is disconnected from the first part of the small intestine (the duodenum). The surgeon then reconnects the stomach to a portion of intestine slightly further 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 gastric bypass are typically performed during the same surgery. Together, this surgery is called a "roux-en-Y gastric bypass." The roux-en-Y procedure accounts for about 80% of all U.S. weight loss surgery procedures.
Usually, gastric bypass is performed laparoscopically (using tools inserted through small incisions in the belly). When laparoscopy is not possible, gastric bypass can be open (laparotomy). This involves a large incision in the middle of the belly.
What to Expect After Gastric Bypass Surgery
Nearly 10% of people have complications after gastric bypass surgery. These are usually minor and include:
Nearly 1% to 5% of people have serious or life-threatening complications after gastric bypass surgery, such as:
Blood clot (pulmonary embolism)
Leak in the surgical connections with the intestines
Serious infection or bleeding
The risk of complications is lower at centers that perform more than 100 weight loss surgeries per year. And, when performed by a highly experienced surgeon, deaths in the month following gastric bypass surgery are rare: about 0.2% to 0.5% (less than one in 200 people).
After gastric bypass surgery, people typically stay in the hospital for two to three days and return to normal activity within two to three weeks.
Weight loss after gastric bypass surgery is often dramatic. On average, patients lose 60% of their extra weight. For example, a 350-pound person who is 200 pounds overweight would lose about 120 pounds.