The surgeon divides the stomach into 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 how much food it can hold.
Part Two: Bypass
The surgeon disconnects the new, small stomach pouch from the first part of the small intestine (the duodenum), and then connects it to a part 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 curbs your absorption of calories and nutrients. This weight loss method is called "malabsorptive."
Stomach stapling and Roux-en-Y are typically done during the same surgery and together are called a "Roux-en-Y gastric bypass."
Usually, surgeons do both laparoscopically (using tools inserted through small cuts in the belly). When laparoscopy isn’t possible, surgeons may do a laparotomy (involving a large cut in the middle of the belly).
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. About 10% of people have complications, which are usually minor and include:
Nearly 1% to 5% of people have serious or life-threatening complications, such as:
Leak in the surgical connections with the intestines
Serious infection or bleeding
The risk of complications is lower at centers that do more than 100 weight loss surgeries per year. Deaths in the month following gastric bypass surgery are very rare (about 0.2% to 0.5%, or less than one in 200 people) when the procedure is done by a highly experienced surgeon.
Other health problems can also happen as a result of the surgery. For example, not absorbing as much of nutrients like iron and calcium can cause anemia and osteoporosis. But taking nutritional supplements and getting blood tests can make that less likely.
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.
But losing weight and keeping it off takes lasting lifestyle changes, like eating several small meals a day and getting regular exercise.