Guide to Gastric Bypass Surgery

Reviewed by weight loss surgeon Francisco Guzman, MD, February 2024

Roux-en-Y Gastric bypass, or simply ‘gastric bypass,’ is one of the most common forms of weight loss surgery in the United States. It results in reliable weight loss with acceptable risks and minimal side effects.

Gastric bypass by various techniques has been performed for over 50 years, making it the operation with the most experience. In gastric bypass surgery, the surgeon staples off a large section of the stomach, creating a tiny pouch and then connects the small intestine to the pouch. Patients simply can't eat as much as they did before surgery because this small pouch can only accommodate a few ounces of food at a time. When the pouch fills with food a feeling of fullness or satiety occurs. The reconnected intestine causes the food to bypass part of the intestine so some of the nutrients and calories in food will not be absorbed. Patients subsequently lose weight. Any patient who is a candidate for bariatric surgery is potentially a candidate for this operation.

It is important that patients who have had a gastric bypass procedure make a lifelong commitment to making the necessary changes in their diet. This includes maintaining an adequate intake of protein, taking vitamin and mineral supplements including a multivitamin, B12, iron and calcium, and avoiding sweets and fatty foods.

Laparoscopic Gastric Bypass Surgery

Since 1997, the Columbia University Center for Metabolic and Weight Loss Surgery has been performing a laparoscopic gastric bypass procedure, and is currently a leader in robotic bariatric approaches as well. In minimally invasive operations, surgical instruments are inserted through small incisions rather than a large one. Patients benefit by having a much smaller wound with faster recovery time than with traditional surgery. These smaller wounds have a lower risk of infection and hernia formation. Scarring is also less with improved cosmetics.

Success Rates for Gastric Bypass Surgery

Estimated weight loss in the first 1-2 years after a Roux-en-Y gastric bypass is approximately 50-65% of excess weight. This usually averages out to 1-2 pounds per week until a new baseline weight is achieved. Compliance with diet recommendations and exercise contribute to final weight. 50% excess weight loss has been documented 10 years and more after gastric bypass. In addition, the comorbidities or illnesses associated with obesity significantly improve. This includes a greater than 80% resolution in diabetes and greater than 90% resolution of sleep apnea. How weight loss can affect you directly to improve your health should be discussed with your physician.

Risks of Gastric Bypass Surgery

Aside from limiting food intake, gastric bypass surgery achieves weight loss by decreasing intestinal absorption of nutrients; instead of following its usual path, food bypasses a portion of the stomach and small bowel. This can lead to long-term deficiencies of vitamin B12, folate, iron and other vitamins and minerals if dietary supplement recommendations are not followed. "Dumping syndrome," in which the consumption of sugar causes abdominal cramping and diarrhea can also occur. Overly fatty and greasy foods may also not be tolerated well. Weight regain in subsequent years can occur especially when post-operative recommendations are not observed.

The reported risk for gastric bypass surgery is the same as the risk for any operation on an obese patient. There is a mortality rate (risk of death) of 0.2%. Operative complications such as bleeding or intestinal leakage can occur in less than 2% of patients. Long term complications related to the intestinal reconnection can also occur. A detailed discussion of the risks of surgery should be a part of your pre-operative discussion with your surgeon.

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