Natalie Digate Muth by Natalie Digate Muth
Gastric Bypass Surgery

The Roux-en-Y gastric bypass procedure involves creating a stomach pouch out of a small portion of the stomach and attaching it directly to the small intestine, bypassing a large part of the stomach and duodenum. Not only is the stomach pouch too small to hold large amounts of food, but by skipping the duodenum, fat absorption is substantially reduced.

Update Date: 5/17/2010

Updated by: Shabir Bhimji MD, PhD, Specializing in Cardiothoracic and Vascular Surgery, Midland , TX Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

Source: Medline Plus, a service of the U.S. National Library of Medicine, NIH, National Institutes of Health

Sometimes a healthy diet and exercise alone are not enough to fight obesity. For people who are severely obese, gastric bypass may be the answer to help drop significant amounts of weight which in turn leads to decreased health risk and increased quality of life. But does gastric bypass really work? That is, do people really lose all that weight and more importantly keep it off?


Gastric bypass is a procedure in which surgeons reduce the stomach to about the size of an egg and then reattach it to the small intestine (see diagram). During the surgery, the vast majority of the stomach and about two feet of the small intestine are stapled shut, or bypassed. This procedure leads to weight loss for two reasons: first, the small stomach pouch cannot hold very much food, so caloric intake is dramatically reduced. Second, by bypassing two feet of the small intestine (where the majority of nutrient absorption occurs), fewer calories and nutrients are absorbed.


Ideal candidates for weight loss surgery are people who are (1) severely obese (BMI>40) OR obese (BMI>35) with  other high-risk conditions such as diabetes, sleep apnea or life-threatening cardiopulmonary problems; (2) an “acceptable” operative risk determined by age, degree of obesity and other pre-existing medical conditions; (3) previously unsuccessful at weight loss with a program integrating diet, exercise, behavior modification and psychological support; and (4) carefully selected by a multidisciplinary team who have medical, surgical, psychiatric and nutritional expertise.  Weight loss surgery is not recommended for the overweight or mildly obese person who is trying to lose 20 or 30 pounds. Furthermore, only those patients who are committed to permanent lifestyle changes--including regular physical activity and a healthy diet--are considered good candidates for surgery.


On average, people who get gastric bypass end up losing about 60% of their excess body weight (excess weight refers to current weight – ideal body weight)1 and maintain a weight loss of about 16% during the 10 year-period following surgery2. They also have an improvement in a variety of other health indicators such as blood pressure, cholesterol, insulin sensitivity and quality of sleep1.  However, many people who are not ready to make the lifestyle changes necessary to maintain the weight loss find ways to cheat the surgery, and gain most or all of their weight back. And, while gastric bypass is very safe, any type of surgery is never without risks. One of every 200 people who gets bypass surgery dies as a result of the procedure1; another 20 experience major morbidity such as infections, bleeding, nutritional deficiencies, blood clots, respiratory failure and bowel obstruction3.


At the end of the day, gastric bypass is a useful tool to lose weight for select people. But – no surprise here -- successful weight loss maintenance even after surgery requires healthy nutrition habits and regular physical activity.


If you’ve had gastric bypass surgery and are looking for ways to safely stay physically active, read the ACE Ask the Expert blog post on Exercise Precautions After Gastric Bypass Surgery from ACE’s Chief Science Officer, Cedric Bryant, PhD.  

  1. Buchwald H, Avidor Y, Braunwald E, et al. Bariatric surgery: a systematic review and meta-analysis. JAMA 2004;292:1724-37.
  2. Sjostrom L, Lindroos AK, Peltonen M, et al. Lifestyle, diabetes, and cardiovascular risk factors 10 years after bariatric surgery. N Engl J Med 2004;351:2683-93.
  3. Steinbrook R. Surgery for severe obesity. N Engl J Med 2004;350:1075-9.

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