Guide to Gastric Bypass Surgery
Reviewed by weight loss surgeon Francisco Guzman, MD, January 2025
Gastric bypass is a surgical procedure that induces weight loss by changing the anatomy of the digestive tract.
Key Facts
- Gastric bypass surgery is one of the most common weight loss surgeries in the United States.
- The surgery shrinks the size and capacity of the stomach, making patients feel full sooner.
- Gastric bypass surgery also reroutes the intestines, reducing the amount of calories and nutrients absorbed during digestion.
What is a Gastric Bypass?
Roux-en-Y Gastric bypass, or simply 'gastric bypass,' is one of the most common forms of weight loss surgery in the United States.
Why Have a Gastric Bypass?
Gastric bypass surgery can help you lose excess weight and reduce your risk of other life-threatening health problems. It is usually an option for obese patients who have struggled to lose weight using diet and exercise. It is particularly helpful for patients who, in addition to wanting to lose weight, suffer from gastroesophageal reflux disease or diabetes.
By losing excess weight, other illnesses associated with obesity can greatly improve. Results have shown a significant reduction in conditions like high blood pressure, diabetes and sleep apnea. Losing weight also greatly improves patients’ mobility, decreases joint pain, among numerous other benefits.
You should discuss how weight loss can improve your health with your physician.
Am I a Candidate for Gastric Bypass Surgery?
Any patient who is a candidate for bariatric surgery is potentially a candidate for this operation. The typical criteria eligible for weight loss surgery include the following:
- Persons with a BMI of 40 or over (about 100 pounds or more above ideal body weight).
- Persons with a BMI of 35 or above (at least 80 pounds above ideal body weight) and who have life-threatening obesity-related problems such as diabetes, hypertension, and sleep apnea.
What Options Do I Have for My Procedure?
Gastric bypass can be performed using minimally invasive approaches, such as laparoscopic/robotic surgery, which uses small incisions. Patients benefit from having a much smaller wound with faster recovery time than with traditional surgery. These smaller incisions also have a lower risk of infection and hernia formation. Scarring is also reduced.
Since 1997, the Columbia University Center for Metabolic and Weight Loss Surgery has been performing minimally invasive gastric bypass procedures. We are also a leader in robotic bariatric approaches.
Watch the Video: Robotic Weight Loss Surgery
How is a Gastric Bypass Performed?
In gastric bypass surgery, the surgeon staples off a large section of the stomach, creating a tiny pouch. The surgeon then connects the small intestine to the pouch.
How Does the Procedure Cause Weight Loss?
When the pouch fills with food, a feeling of fullness or satiety occurs. 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.
Shrinking the stomach also reduces the body's level of ghrelin, commonly referred to as the "hunger hormone." It also positively affects the levels of GLP-1, another “peptide” that helps regulate blood sugar and satiety.
Ghrelin also plays a role in blood sugar metabolism. People with type II diabetes often see an immediate decrease in their need for diabetes medications (especially oral medications) after the procedure.
The reconnected intestine also causes food to bypass part of the intestine, so some of the nutrients and calories in food will not be absorbed. Patients subsequently lose weight.
Stories & Perspectives
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What Kind of Anesthesia is Used During the Surgery?
A gastric bypass is performed under general anesthesia, so you will not be awake during the procedure.
How Do I Prepare for My Gastric Bypass Surgery?
Your surgeon will give you specific instructions to help make your procedure more successful. These include adhering to a special diet and discontinuing smoking and certain medications prior to your surgery.
What are the Risks of a Gastric Bypass Surgery?
Like any surgery, a gastric bypass carries a very low risk for complications. Some potential risks that are specific to the procedure include:
- Dumping Syndrome – Food moving quickly from the stomach into the small intestine can cause uncomfortable symptoms, including nausea, vomiting, diarrhea, cramping, and fatigue.
- Stomach Leakage – The seam where the stomach has been stapled back together may leak.
- Food restrictions – Overly fatty and greasy foods may not be tolerated well.
- Complications at Reconnection Site – Long-term complications related to intestinal reconnection can also occur.
- Long-term Nutrient Deficiencies – Changes in how your body digests food can lead to long-term deficiencies of vitamin B12, folate, iron, and other vitamins and minerals if dietary supplement recommendations are not followed.
It's important to remember that while gastric bypass surgery is reversible, the reversal procedure is risky. And as with any weight loss surgery, you may not achieve the desired weight loss results.
A detailed discussion of the risks of surgery should be a part of your preoperative discussion with your surgeon.
What is Recovery Like After a Gastric Bypass?
For the first few weeks after surgery, you will need to follow a carefully monitored diet, starting with a liquid diet and slowly reintroducing specific types of food. Most patients find that after a reasonable recovery, they can comfortably eat a wide variety of foods, including meats and fibrous vegetables.
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 eating enough protein, taking vitamin and mineral supplements, and avoiding sweets and fatty foods.
How Much Weight Will I Lose?
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.
How Long Will the Benefits of a Gastric Bypass Last?
How well you comply with diet recommendations and exercise will greatly contribute to your final weight. With smart food choices, regular exercise, and good eating habits, patients who have had gastric bypass surgery have maintained 50% excess weight loss for 10 years or more.
Next Steps
If you'd like to learn more about having gastric bypass surgery or other weight-loss procedures, our team at Columbia is here to help. Call us at (212) 305-4000 or request an appointment online. We accept a number of insurance plans, and our team can help confirm your coverage.