Gastric Bypass Surgery

The gastric bypass, or “Roux-en-Y," is a medical weight loss procedure. It works by modifying your digestive system. Gastric bypass surgery reduces the size of your stomach, and also the length of your small intestine. As a result, you consume and absorb fewer calories.


What is gastric bypass surgery?

Gastric bypass surgery is a metabolic and weight loss procedure. It’s also known by the French term, “Roux-en-Y." The procedure works by modifying your digestive system so that you consume and absorb fewer calories. It modifies your stomach and also your small intestine.


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Who is gastric bypass surgery for?

Like other bariatric surgery operations, gastric bypass is recommended for people who have clinically severe obesity. It has been shown to help relieve a long list of obesity-related health conditions, including type 2 diabetes, hypertension, obstructive sleep apnea and GERD (chronic acid reflux).

What does gastric bypass surgery do?

The Roux-en-Y procedure gets its name from the way it changes your digestive system. “Roux-en-Y" means “in the shape of a Y." The procedure divides both your stomach and your small intestine, connecting each new segment together to form a “Y” shape.


How does Roux-en-Y surgery work?

First, it reduces the functional part of your stomach to a small pouch, separating it from the rest with surgical staples. This restricts the amount of food that your stomach can hold. Then, it connects the new stomach pouch to a lower segment of your small intestine.

This means that when food goes through your digestive system, it will now bypass most of your stomach and the first part of your small intestine. Because of this bypass, your digestive system won’t absorb all of the nutrients (or calories) in your food.

How common is gastric bypass surgery?

The Roux-en-Y procedure has been practiced, studied and refined for over 50 years. It was once the most common weight loss surgery, but in recent years it’s been overtaken by the gastric sleeve. Today the gastric bypass represents about 18% of all bariatric surgeries.


Is gastric bypass a serious surgery?

Yes. While it is considered a safe procedure, comparable to many other common surgeries, a gastric bypass is a major operation that will change your digestive system forever. Even after recovery, you will have to continue to take special care of it for the rest of your life.

How much weight can you lose with gastric bypass surgery?

Weight loss in the first year or two after surgery is often significant. The average is about 70% of excess weight. Over the longer term, some people gain some weight back, but the average long-term weight loss is 50% of excess weight. That number holds steady for 20 years.

What conditions can gastric bypass surgery help manage or improve?

If you have medically significant obesity, just losing weight can do a lot to improve your health. But gastric bypass surgery does more than that. It makes lasting changes to your metabolic system to help you manage your blood sugar, blood pressure and hunger.

Conditions improved by gastric bypass surgery include:

Procedure Details

Illustration showing how gastric bypass surgery modifies the stomach and small intestine.
Gastric bypass surgery divides your stomach and your small intestine. The new "branch" of the intestine connects to the new stomach "pouch".

What are the requirements to qualify for gastric bypass surgery?

Gastric bypass surgery requirements are similar to those of other bariatric procedures. You must be recommended for surgery by a qualified healthcare provider. In general, you may be a candidate for gastric bypass surgery if you:

  • Have been diagnosed with class III obesity. This is determined by your BMI (body mass index). Class III obesity means a BMI of at least 40 kg/m2
  • Have a BMI of at least 35 with at least one obesity-related condition.
  • Have obesity-related type 2 diabetes. Because of its positive effects on blood sugar regulation, you may qualify for gastric bypass surgery to help manage your type 2 diabetes, if it’s unmanaged and you have a BMI of 30 or higher.

If you’ve met these benchmarks, you may be recommended for surgery. But your surgeon will have additional requirements. Before scheduling your surgery, you’ll meet with a team of healthcare specialists for counseling and screening. They’ll want to know:

  • That you're committed to lifelong lifestyle changes. Surgery is a powerful tool for weight loss, but it won’t work if you won’t work with it. You’ll have to change the way you eat forever. If you don’t, you could regain the weight you lose.
  • That you’re physically and mentally fit for surgery. You’ll likely take some standard medical tests to make sure the procedure will be safe for you. You may also be screened for mental health and for alcohol or tobacco use.
  • That you’ve tried to lose weight by other means. Health insurance companies may ask you to prove that weight loss surgery is medically necessary. They may require that you try a supervised diet and exercise program first.

How is gastric bypass surgery performed?

Most Roux-en-Y surgery operations today are performed by laparoscopy, a minimally-invasive surgery technique. The laparoscopic gastric bypass was introduced almost 30 years ago and has since become the standard of care for most people.

Laparoscopic surgery involves three to five small incisions in your abdomen, each about a half an inch. Smaller cuts mean fewer complications, less bleeding, less pain and a faster recovery. Your surgeon will perform the operation through these openings, using long, narrow tools.

Sometimes laparoscopic operations such as Roux-en-Y are done with robotic assistance. Robotic surgery is still controlled by the surgeon. It just means that the surgeon attaches robotic arms to the laparoscopic tools. They control the arms with a computer.

While 90% of Roux-en-Y surgeries are performed laparoscopically, some people may need to have open surgery to manage their specific conditions. Rarely, some laparoscopic Roux-en-Y surgeries may need to convert to open surgeries to be completed safely.

What happens during the Roux-en-Y procedure?

All laparoscopic surgeries begin with a single “keyhole incision” in your abdomen. Your surgeon uses this first keyhole to inflate your abdominal cavity with carbon dioxide gas. This helps separate your abdominal wall from your organs and makes everything easier to see.

Then your surgeon will place a tiny lighted video camera called a laparoscope through the keyhole to visualize your organs. The laparoscope will project onto a computer screen. Your surgeon will use additional keyhole incisions to access your organs.

The first step in the Roux-en-Y procedure is to divide the top portion of your stomach from the remainder with a surgical stapler. The resulting pouch is about the size of an egg. The remainder of the stomach is still attached to your small intestine.

The next step is to divide your small intestine several feet down its length and bring the lower segment up to attach to your new stomach pouch. Your food will now pass from your stomach pouch into this segment of your lower small intestine.

The final step is to reattach the upper branch of your small intestine to the trunk further down. Now your small intestine has two branches attached to the trunk: one leading from your stomach pouch, and the other leading from the remainder of your stomach.

The right side of this “Y” is the new branch, the one that your food will pass through. The left side is the original upper part of your small intestine (your duodenum). This is the part where your liver, gallbladder and pancreas deliver their digestive juices.

The left branch will deliver these juices into the new trunk of your small intestine, where they will mix with your food. This will enable you to properly digest your food, even though your shortened intestinal pathway will absorb fewer nutrients from it.

How long does gastric bypass surgery take?

The procedure itself takes between two to four hours. Afterward, you’ll probably remain in the hospital for two days. You won’t be able to eat solid foods yet.

How painful is gastric bypass surgery?

You’ll feel moderate pain in the first few days, but you’ll have pain medication on demand through a catheter in your vein. You won’t be discharged from the hospital until you’ve weaned from your pain medication and are able to move around comfortably on your own.

At home, you’ll have prescription pain medications to take. Most people wean from these within a week. You may continue to feel your incision wounds while they heal, but the smaller laparoscopic surgery incisions heal relatively quickly.

Risks / Benefits

What are the advantages of Roux-en-Y surgery?

This procedure has the advantage of decades of practice behind it. It’s one of the most thoroughly studied surgeries in modern medicine. Compared to other weight loss procedures, it has one of the best success rates over the long term.

Follow-up studies of gastric bypass surgeries have shown consistent, significant weight loss decades later. Along with weight loss, many related health conditions improve or even resolve. Many people are able to discontinue medications for these conditions.

What are the possible risks of the procedure?

In the short term, gastric bypass surgery shares the same general risks as many other surgeries, including:

  • Wound infection.
  • Excessive bleeding.
  • Reactions to anesthesia.

Complications more specific to gastric bypass surgery can include:

What are the possible long-term complications of gastric bypass surgery?

Surgeries that modify your digestive system can cause certain digestive complications. These include:

  • Dumping syndrome. This is a collection of symptoms that can occur when your stomach dumps food too fast into your small intestine. Up to 50% of people who have bariatric surgery may have some symptoms of dumping syndrome afterward. Symptoms can include nausea, diarrhea, abdominal cramping and hypoglycemia. They usually fade with time. Your healthcare team will give you dietary guidelines to help prevent or reduce dumping syndrome while you recover.
  • Malabsorption and malnutrition. Gastric bypass surgery intentionally induces malabsorption in your small intestine to reduce the calories you absorb. It can also lead to nutritional deficiencies if you aren’t careful. Your healthcare provider will prescribe nutritional supplements to help prevent this.
  • Bile reflux. Surgery that affects the pyloric valve, the opening between your stomach and your small intestine, can cause it to malfunction. If the pyloric valve doesn’t close properly, one possible result is bile reflux. That means the bile that your gallbladder sends to your small intestine to help digest food can backwash into your stomach. Bile reflux can erode your stomach lining, leading to gastritis and stomach ulcers.
  • Gallstones. Rapid weight loss sends a large load of cholesterol to your liver to process. When your liver sends bile to your gallbladder, it carries extra cholesterol with it. This extra cholesterol can build up in your gallbladder, forming cholesterol gallstones. Gallstones don’t always cause problems, but they can be dangerous if they travel and get stuck in your bile ducts. Your healthcare provider may give you a prescription medication to prevent gallstones after surgery.
  • Ulcers. People who have gastric bypass surgery are more at risk of developing ulcers in their stomach or duodenum. To avoid this, your healthcare provider will advise you to avoid smoking or using NSAIDs (non-steroidal anti-inflammatory drugs) in the future.
  • Weight regain. If you don’t commit to changing the way you eat from now on, it’s possible to stretch out your stomach again. Even the small pouch your surgeon made for you can grow to hold more and more food over time. When this happens, one possible option is gastric bypass revision surgery. Your surgeon may agree to repair or redo your Roux-en-Y.

Recovery and Outlook

What is the recovery time from gastric bypass surgery?

You’ll likely spend a day recovering in the hospital, then a few weeks recovering at home before you feel ready to go back to work. You may need to avoid strenuous activity for up to six weeks, and it may take up to twelve weeks to resume a normal diet.

What side effects might I experience during recovery?

Your body will be experiencing huge shifts during this time. You may notice:

  • Fatigue. Recovery is hard work, and your liquid diet may not provide much energy at first.
  • Mood changes. Weight changes can cause hormone changes, and these cause mood changes.
  • Poop changes. Your shortened small intestine won’t be able to digest or absorb water from your food as fully as it did before. This affects the consistency and smell of your poop.

The rapid weight loss and limited nutrition of the first few months may cause:

  • Cold.
  • Body aches.
  • Hair loss.

What kind of diet will I have to follow after gastric bypass surgery?

You will have strict dietary guidelines to follow for several months after your surgery. This is both to protect your digestive system while it heals and to make sure you get the nutrients you need while taking in less food overall.

You’ll probably start on a liquid diet for the first several weeks, then gradually progress to a soft diet for several more. It might be two to three months before you return to solid foods. When you do, you will have to continue to choose your foods carefully.

Your healthcare team will provide you with more specific dietary guidelines, but they generally include:

  • Consuming at least 64 ounces of fluids a day. This can be challenging, due to your reduced stomach size, especially since you’ll be advised not to drink while eating. But hydration is very important following surgery to avoid unpleasant side effects, such as nausea and constipation.
  • Consuming at least 100 grams of protein a day. Protein is the most important macronutrient you’ll need to stay strong after surgery and prevent muscle loss. Staying focused on protein sources will help you get more mileage out of the calories you consume and avoid less nutritious choices.
  • Taking vitamin and mineral supplements daily. You’ll need to take micronutrient supplements for the rest of your life. Your digestive system will no longer be able to absorb enough of them from your food alone. Vitamin and mineral deficiencies can have serious health effects.
  • Avoiding foods high in sugar and starch. While this is good general advice for maintaining weight loss, there is a more important reason why you’ll need to avoid these foods following surgery. It has to do with how quickly food will pass from your stomach to your small intestine now. Concentrated doses of carbohydrates (sugars) entering your small intestine can cause uncomfortable side effects, such as indigestion and rapid blood sugar changes.

What kind of follow-up care can I expect after gastric bypass?

You’ll have regular checkups with your healthcare provider over the following months and years. They’ll monitor your general health and weight loss, test you for nutritional deficiencies and continue to provide counseling on the diet and lifestyle changes you’re implementing.

A note from Cleveland Clinic

Gastric bypass surgery is a serious lifelong commitment, but it can provide significant lifelong changes. If you’re prepared to take more intensive care of yourself, eating more mindfully and exercising regularly, surgery can make these changes work for you like never before.

While there is some risk of long-term complications, these can usually be avoided by following self-care guidelines. Compared to the risks of obesity itself and its related health conditions, most people find these risks well worth the reward of weight loss and recovery.

Medically Reviewed

Last reviewed on 04/11/2022.

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