Gastric bypass surgery makes the stomach smaller and allows food to bypass part of the small intestine. You will feel full more quickly than when your stomach was its original size, which reduces the amount of food you eat and thus the calories consumed. Bypassing part of the intestine also results in fewer calories being absorbed. This leads to weight loss.
The most common gastric bypass surgery is a Roux-en-Y gastric bypass.
In normal digestion, food passes through the stomach and enters the small intestine, where most of the nutrients and calories are absorbed. It then passes into the large intestine (colon), and the remaining waste is eventually excreted.
In a Roux-en-Y gastric bypass, the stomach is made smaller by creating a small pouch at the top of the stomach using surgical staples or a plastic band. The smaller stomach is connected directly to the middle portion of the small intestine (jejunum), bypassing the rest of the stomach and the upper portion of the small intestine (duodenum).
This procedure can be done by making a large incision in the abdomen (an open procedure) or by making a small incision and using small instruments and a camera to guide the surgery (laparoscopic approach).
See a picture of a Roux-en-Y gastric bypass.
What To Expect After Surgery
Most people can return to their normal activities in 3 to 5 weeks.
After surgery, you'll need to make big, permanent changes in how you eat:
- You can eat only a few ounces of food at a time. Your new stomach will only hold a tiny amount of food.
- You must eat very slowly and chew your food to mush. Otherwise, you may vomit often and have pain.
- You won't be able to drink for 30 minutes before you eat, during your meal, and for 30 minutes after you eat. There won't be room in your stomach for both drinks and solid food.
- You probably will need to take vitamins and supplements.
- You may have to avoid foods that contain simple sugars—like candy, juices, ice cream, condiments, and soft drinks. Simple sugars may cause a problem called dumping syndrome. This happens because food moves too quickly through the stomach and intestines. It can cause shaking, sweating, dizziness, rapid heart rate, and often severe diarrhea.
Why It Is Done
Although guidelines vary, surgery is generally considered when your body mass index is 40 or higher or you have a life-threatening or disabling condition related to your weight.
Your doctor may only consider doing gastric bypass surgery if you have not been able to lose weight with other treatments.
The following conditions may also be required or are at least considered:
- You have been obese for at least 5 years.
- You do not have an ongoing problem with alcohol.
- You do not have untreated depression or another major psychiatric disorder.
- You are between 18 and 65 years of age.
All surgeries have risk. And it is important for you and your doctor to discuss your treatment options to decide what is best for you.
How Well It Works
Most people who have gastric bypass surgery quickly begin to lose weight and continue to lose weight for up to 12 months. One study noted that people lost about one-third of their excess weight (the weight above what is considered healthy) in 1 to 4 years.1 Some of the lost weight may be regained.
The laparoscopic approach showed similar results, with 69% to 82% of excess weight lost over 12 to 54 months.2
Risks common to all surgeries for weight loss include an infection in the incision, a leak from the stomach into the abdominal cavity or where the intestine is connected (resulting in an infection called peritonitis), and a blood clot in the lung (pulmonary embolism). About one-third of all people having surgery for obesity develop gallstones or a nutritional deficiency condition such as anemia or osteoporosis.3, 4
Fewer than 10 out of 1000 people die after weight-loss surgery.5
- An iron and vitamin B12 deficiency occurs more than 30% of the time. About 50% of those with an iron deficiency develop anemia.
- The connection between the stomach and the intestines narrows (stomal stenosis) 5% to 15% of the time, leading to nausea and vomiting after eating.
- Ulcers develop 5% to 15% of the time.
- The staples may pull loose.
- Hernia may develop.
- The bypassed stomach may enlarge, resulting in hiccups and bloating.
What To Think About
Gastric bypass surgery may increase your chances of living longer. Some studies show that people who have weight-loss surgery have a smaller chance of dying of heart problems, diabetes, or cancer.7
In a gastric bypass, the part of the intestine where many minerals and vitamins are most easily absorbed is bypassed. Because of this, you may have a deficiency in iron, calcium, magnesium, or vitamins. This can lead to long-term problems, such as osteoporosis. To prevent vitamin and mineral deficiencies, you may need to work with a dietitian to plan meals, and you may need to take extra vitamin B12 as pills, shots, or nasal spray.
There is also a possibility that you may develop gallstones after gastric bypass. Sometimes the gallbladder is removed as part of the surgery. But if your gallbladder is not removed, then you may need to take medicine to prevent gallstones.4, 8
Early studies of the laparoscopic approach to surgery for obesity suggest that it reduces recovery time and postsurgery complications.2
- Balsiger BM, et al. (2000). Prospective evaluation of Roux-en-Y gastric bypass surgery as primary operation for medically complicated obesity. Mayo Clinic Proceedings, 75(7): 673–680.
- Schauer PR, Ikramuddin S (2001). Laparoscopic surgery for morbid obesity. Surgical Clinics of North America, 81(5): 1145–1179.
- American Gastroenterological Association (2002). AGA technical review on obesity. Gastroenterology, 123(3): 882–932. [Erratum in Gastroenterology, 123(5): 1752.
- U.S. Department of Health and Human Services (2008). Bariatric Surgery for Severe Obesity (NIH Publication No. 04-4006). Available online: http://www.win.niddk.nih.gov/publications/gastric.htm.
- Maggard M, et al. (2005). Meta-analysis: Surgical treatment of obesity. Annals of Internal Medicine, 142: 547–559.
- Brolin RE (2002). Bariatric surgery and long-term control of morbid obesity. JAMA, 288(22): 2793–2796.
- Adams TD, et al. (2007). Long-term mortality after gastric bypass surgery. JAMA, 357(8): 753–761.
- U.S. Department of Health and Human Services (2008). Dieting and Gallstones (NIH Publication No. 02–3677). Available online: http://www.win.niddk.nih.gov/publications/gallstones.htm.
Last Updated: April 16, 2009