Health Information

Gastric bypass surgery


Gastric bypass is surgery that helps you lose weight by changing how your stomach and small intestine handle the food you eat.

After the surgery, your stomach will be smaller. You will feel full with less food.

The food you eat will no longer go into some parts of your stomach and small intestine that absorb food. Because of this, your body will not get all of the calories from the food you eat.

Alternative Names

Bariatric surgery - gastric bypass; Roux-en-Y gastric bypass; Gastric bypass - Roux-en-Y; Weight-loss surgery - gastric bypass; Obesity surgery - gastric bypass


You will have general anesthesia before this surgery. You will be asleep and pain free.

There are two steps during gastric bypass surgery:

  • The first step makes your stomach smaller. Your surgeon uses staples to divide your stomach into a small upper section and a larger bottom section. The top section of your stomach (called the pouch) is where the food you eat will go. The pouch is about the size of a walnut. It holds only about 1 ounce (oz) of food. Because of this you will eat less and lose weight.
  • The second step is the bypass. Your surgeon connects a small part of your small intestine (the jejunum) to a small hole in your pouch. The food you eat will now travel from the pouch into this new opening and into your small intestine. As a result, your body will absorb fewer calories.

Gastric bypass can be done in two ways. With open surgery, your surgeon makes a large surgical cut to open your belly. The bypass is done by working on your stomach, small intestine, and other organs.

Another way to do this surgery is to use a tiny camera, called a laparoscope. This camera is placed in your belly. The surgery is called laparoscopy. The scope allows the surgeon to see inside your belly.

In this surgery:

  • The surgeon makes 4 to 6 small cuts in your belly.
  • The scope and instruments needed to perform the surgery are inserted through these cuts.
  • The camera is connected to a video monitor in the operating room. This allows the surgeon to view inside your belly while doing the operation.

Advantages of laparoscopy over open surgery include:

  • Shorter hospital stay and quicker recovery.
  • Less pain.
  • Smaller scars and a lower risk of getting a hernia or infection.

This surgery takes about 2 to 4 hours.

Why the Procedure Is Performed

Weight-loss surgery may be an option if you are very obese and have not been able to lose weight through diet and exercise.

Doctors often use the body mass index (BMI) and health conditions such as type 2 diabetes and high blood pressure to determine which patients are most likely to benefit from weight-loss surgery.

Gastric bypass surgery is not a quick fix for obesity. It will greatly change your lifestyle. After this surgery, you must eat healthy foods, control portion sizes of what you eat, and exercise. If you do not follow these measures, you may have complications from the surgery and poor weight loss.

This procedure may be recommended if you have:

  • BMI of 40 or more. Someone with a BMI of 40 or more is at least 100 pounds over their recommended weight. A normal BMI is between 18.5 to 25.
  • A BMI of 35 or more and a serious medical condition that might improve with weight loss. Some of these conditions are obstructive sleep apnea, type 2 diabetes, and heart disease.


Gastric bypass is major surgery and it has many risks. Some of these risks are very serious. You should discuss these risks with your surgeon.

Risks for anesthesia and surgery in general include:

  • Allergic reactions to medicines
  • Breathing problems
  • Bleeding, blood clots, infection
Risks for gastric bypass include:
  • Gastritis (inflamed stomach lining), heartburn, or stomach ulcers
  • Injury to the stomach, intestines, or other organs during surgery
  • Leaking from the line where parts of the stomach have been stapled together
  • Poor nutrition
  • Scarring inside your belly that could lead to a blockage in your bowel in the future
  • Vomiting from eating more than your stomach pouch can hold

Before the Procedure

Your surgeon will ask you to have tests and visits with other health care providers before you have this surgery. Some of these are:

  • A complete physical exam.
  • Blood tests, ultrasound of your gallbladder, and other tests to make sure you are healthy enough to have surgery.
  • Visits with your doctor to make sure other medical problems you may have, such as diabetes, high blood pressure, and heart or lung problems, are under control.
  • Nutritional counseling.
  • Classes to help you learn what happens during the surgery, what you should expect afterward, and what risks or problems may occur afterward.
  • You may want to visit with a counselor to make sure you are emotionally ready for this surgery. You must be able to make major changes in your lifestyle after surgery.

If you smoke, you should stop several weeks before surgery and not start smoking again after surgery. Smoking slows recovery and increases the risks of problems. Tell your doctor or nurse if you need help quitting.

Tell your surgeon or nurse:

  • If you are or might be pregnant
  • What medicines, vitamins, herbs, and other supplements you are taking, even ones you bought without a prescription

During the week before your surgery:

  • You may be asked to stop taking medicines that make it hard for your blood to clot. These include aspirin, ibuprofen (Advil, Motrin), vitamin E, warfarin (Coumadin), and others.
  • Ask your doctor which drugs you should still take on the day of your surgery.
  • Prepare your home for after the surgery.

On the day of  surgery:

  • Follow instructions about when to stop eating and drinking.
  • Take the drugs your doctor told you to take with a small sip of water.
  • Arrive at the hospital on time.

After the Procedure

Most people stay in the hospital for 1 to 4 days after surgery.

In the hospital:

  • You will be asked to sit on the side of the bed and walk a little on the same day you have surgery.
  • You may have a (tube) catheter that goes through your nose into your stomach for 1 or 2 days. This tube helps drain fluids from your intestine.
  • You may have a catheter in your bladder to remove urine.
  • You will not be able to eat for the first 1 to 3 days. After that, you can have liquids and then pureed or soft foods.
  • You may have a tube connected to the larger part of your stomach that was bypassed. The catheter will come out of your side and will drain fluids.
  • You will wear special stockings on your legs to help prevent blood clots from forming.
  • You will receive shots of medicine to prevent blood clots.
  • You will receive pain medicine. You will take pills for pain or receive pain medicine through an IV, a catheter that goes into your vein.

You will be able to go home when:

  • You can eat liquid or pureed food without vomiting.
  • You can move around without a lot of pain.
  • You do not need pain medicine through an IV or given by shot.

Be sure to follow instructions for how to care for yourself at home.

Outlook (Prognosis)

Most people lose about 10 to 20 pounds a month in the first year after surgery. Weight loss will decrease over time. By sticking to your diet and exercise from the beginning, you lose more weight.

You may lose half or more of your extra weight in the first 2 years. You will lose weight quickly after surgery if you are still on a liquid or pureed diet.

Losing enough weight after surgery can improve many medical conditions, including:

Weighing less should also make it much easier for you to move around and do your everyday activities.

To lose weight and avoid complications from the procedure, you will need to follow the exercise and eating guidelines that your doctor and dietitian have given you.


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Buchwald H. Open Roux-en-Y gastric bypass. In: Buchwald H. Buchwald's Atlas of Metabolic and Bariatric Surgical Techniques and Procedures. Philadelphia, PA: Elsevier Saunders; 2012:chap 5.

Pontiroli AE, Morabito A. Long-term prevention of mortality in morbid obesity through bariatric surgery: A systematic review and meta-analysis of trials performed with gastric banding and gastric bypass. Ann Surg. 2011;253:484-487. Available at:

Richards WO. Morbid obesity. In: Townsend Jr. CM, Beauchamp RD, Evers BM, Mattox KL. Sabiston Textbook of Surgery. 19th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 15.

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Review Date: 3/31/2015
Reviewed By: Ann Rogers, MD, Associate Professor of Surgery; Director, Penn State Surgical Weight Loss Program, Penn State Milton S. Hershey Medical Center, Hershey, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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