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Gastric Bypass Surgery

Surgery Overview

A gastric bypass (also called Roux-en-Y gastric bypass) is surgery to help you lose weight. It does this in two ways. First, it makes the stomach smaller. Second, it changes the connection between the stomach and the intestines. These changes help you eat less and feel full sooner.

This procedure can be done in two ways:

  • By making several small cuts and using small tools and a camera to guide the surgery (laparoscopic approach).
  • By making one cut (open approach).

The laparoscopic approach is used most often.

You will be asleep during the surgery. The doctor will separate the upper part of your stomach from the rest of your stomach. This forms a small pouch. This new pouch will hold the food you eat. The doctor will connect the new stomach pouch to the middle part of your small intestine. Then the doctor will close the incisions with stitches. The incisions leave scars that fade with time.

After the surgery, the food you eat will go from the small pouch to the middle part of your intestine. Food will no longer go through the lower part of your stomach or the first part of your intestines.

You will stay in the hospital 1 or more days after the surgery. In a laparoscopic surgery, most people can go back to work or their usual routine in about 2 to 4 weeks. In an open surgery, it takes 4 to 6 weeks to get back to usual routines.

What To Expect

You will have some belly pain and may need pain medicine for the first week or so after surgery. The cut that the doctor makes (incision) may be tender and sore.

Most people need 2 to 4 weeks before they are ready to get back to their usual routine.

Because the surgery makes your stomach smaller, you will get full more quickly when you eat. Food also may empty into the small intestine too quickly and lead to dumping syndrome. This can cause diarrhea and make you feel faint, shaky, and nauseated. It also can make it hard for your body to get enough nutrition.

Your doctor will give you specific instructions about what to eat after the surgery. You'll start with only small amounts of soft foods and liquids. Bit by bit, you will be able to add solid foods back into your diet.

This surgery bypasses the part of the intestine where many minerals and vitamins are most easily absorbed. Because of this, you may not get enough iron, calcium, magnesium, or vitamins. It's important to make sure you get enough nutrients in your daily meals 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.

Depending on how the surgery was done (open or laparoscopic), you'll have to watch your activity during recovery. If you had open surgery, make sure to avoid heavy lifting or strenuous exercise while you are recovering so that your belly can heal. In this case, you will probably be able to return to work or your normal routine in 4 to 6 weeks. The surgery is most often done as a laparoscopic procedure. This means the recovery time is faster.

Weight loss

You probably will lose weight very quickly in the first few months after surgery. As time goes on, your weight loss will slow down. You will have regular doctor visits to check how you are doing.


It is common to have many emotions after this surgery. You may feel happy or excited as you begin to lose weight. But you may also feel overwhelmed or frustrated by the changes that you have to make in your diet, activity, and lifestyle. Talk with your doctor if you have concerns or questions.

Think of bariatric surgery as a tool to help you lose weight. It isn't an instant fix. You will still need to eat a healthy diet and get regular exercise. This will help you reach your weight goal and avoid regaining the weight you lose.

What you can eat

Your doctor will give you specific instructions about what to eat after the surgery. For about the first month after surgery, your stomach can only handle small amounts of soft foods and liquids while you are healing. It is important to try to sip water throughout the day to avoid becoming dehydrated. You may notice that your bowel movements are not regular right after your surgery. This is common. Try to avoid constipation and straining with bowel movements.

Bit by bit, you will be able to add solid foods back into your diet. You must be careful to chew food well and to stop eating when you feel full. This can take some getting used to, because you will feel full after eating much less food than you are used to eating. If you don't chew your food well or don't stop eating soon enough, you may feel discomfort or nausea and may sometimes vomit. If you drink a lot of high-calorie liquid such as soda or fruit juice, you may not lose weight. If you continually overeat, the stomach may stretch. If your stomach stretches, you won't benefit from your surgery.

Your doctor will probably recommend that you work with a dietitian to plan healthy meals that give you enough protein, vitamins, and minerals while you are losing weight. Even with a healthy diet, you probably will need to take vitamin and mineral supplements for the rest of your life.


Why It Is Done

A gastric bypass (also called a Roux-en-Y gastric bypass) is suitable for people who are severely overweight and who have not been able to lose weight with diet, exercise, or medicine.

Surgery is generally considered when your body mass index (BMI) is 40 or higher. Surgery may also be an option when your BMI is 35 or higher and you have a life-threatening or disabling problem that is related to your weight.

It is important to think of this surgery as a tool to help you lose weight. It is not an instant fix. You will still need to eat a healthy diet and get regular exercise. This will help you reach your weight goal and avoid regaining the weight you lose.

Learn more


How Well It Works

Research shows that people who have gastric bypass lose more total weight than those who have gastric sleeve or gastric banding. But they also have more complications right after surgery.footnote 1 The long-term success is highest in people who are realistic about how much weight they will lose and who go to appointments with a medical team, follow the recommended eating plan, and are physically active.footnote 2


Here are some risks common to all surgeries for weight loss:

  • You could get an infection in the incision.
  • You could get a blood clot in your legs (deep vein thrombosis, or DVT) or lung (pulmonary embolism).
  • You may not get enough of certain vitamins and minerals. This can lead to problems such as anemia and osteoporosis.
  • Some people get gallstones.
  • Some people get kidney stones.
  • You could get a leak from the stomach into the abdominal cavity or where the intestine is connected. (This can cause an infection called peritonitis.)
  • You may gain the weight back a few years after surgery if you don't follow your eating and lifestyle plan.

Other risks from a gastric bypass (also called a Roux-en-Y gastric bypass) include:

Dumping syndrome.

This causes nausea, weakness, sweating, faintness, and possibly diarrhea soon after eating. These symptoms get worse if you eat highly refined, high-calorie foods (like sweets). Sometimes you may feel so weak that you have to lie down until the symptoms pass.

Stomach pouch problems.

You may need a repeat surgery to repair the stomach and/or the opening between the stomach and the intestine.


If you eat more than your stomach can hold, you may vomit.


This can be related to the incisions that the surgeon makes. Or it can be caused by the intestine twisting around itself.



  1. Arterburn D, et al. (2018). Comparative effectiveness and safety of bariatric procedures for weight loss: A PCORnet cohort study. Annals of Internal Medicine. DOI: 10.7326/M17-2786. Accessed August 21, 2020.
  2. Heber D, et al. (2010). Endocrine and nutritional management of the post-bariatric surgery patient: An Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism, 95(11): 4823–4843. Available online:


Current as of: May 13, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.


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