Gastric Bypass

Medically Reviewed By William C. Lloyd III, MD, FACS

What is gastric bypass?

Gastric bypass is a surgery that can help adults and some adolescents who are very obese (morbidly obese) lose weight. It involves attaching the stomach directly to the middle of the small intestine. This reduces the amount of calories and nutrients that are absorbed by the body. 

Gastric bypass surgery usually includes a stomach stapling procedure. Stomach stapling reduces the size of your stomach and the amount of food you can eat at one time. 

Gastric bypass has serious risks but the benefits can be significant. Benefits include long-term weight-loss and resolution of serious diseases associated with obesity, such as type 2 diabetes, hypertension, and high cholesterol

Gastric bypass is only one part of a complete treatment plan. Plans also include a lifelong commitment to healthy dietary and exercise habits, vitamin supplementation, and regular follow-up care. You may have less invasive treatment options with less risk of complications. Ask your doctor about all your treatment options and consider getting a second opinion before having gastric bypass. 

Types of gastric bypass

Gastric bypass is a malabsorptive procedure. This means that it helps you lose weight by changing the normal process of digestion. Specific gastric bypass procedures include:

  • Biliopancreatic diversion with a duodenal switch (BPD-DS, duodenal switch) involves removing part of the stomach and using staples to create a smaller tube-shaped stomach (vertical sleeve gastrectomy). In another surgery, the stomach is attached to the middle of the small intestine. This bypasses a large part of the small intestine and reduces the amount of calories and nutrients absorbed into the body.

  • Roux-en-Y gastric bypass (RYGB) involves stapling the stomach to create a small pouch. The smaller stomach is attached directly to the middle of the small intestine. This allows food to bypass much of the stomach and the first section of the small intestine. It limits the amount of food that you can eat and reduces the amount of calories and nutrients that are absorbed into the body.

Why is gastric bypass performed? 

Your doctor may recommend gastric bypass to treat obesity and reduces the risk of life-threatening complications of obesity. These include diabetes, heart disease, and severe sleep apnea

Gastric bypass is not a treatment option for people who are mildly overweight. It is generally considered for adults with a body mass index (BMI) of 40 or more. This means being about 100 pounds overweight for men and 80 pounds overweight for women. Certain people who are less obese with a BMI of about 35 to 39.9 with serious weight-related health problems may have gastric bypass. 

Gastric bypass may be a treatment option if other treatments that involve less risk and fewer complications have not helped you lose weight and maintain a healthy weight. Other treatments include diet, exercise, behavioral and nutritional counseling, and medication. People typically need a psychological evaluation prior to the surgery.

Ask your doctor about all of your treatment options and consider getting a second opinion before deciding on gastric bypass. 

Who performs gastric bypass?

A general surgeon or bariatric surgeon performs gastric bypass. General surgeons specialize in the surgical treatment of a variety of diseases and conditions, including those of the stomach and intestines. Bariatric surgeons are usually general surgeons who further specialize in weight-loss surgery.  

How is gastric bypass performed?

Your gastric bypass will be performed in a hospital using one of the following approaches:

  • Minimally invasive surgery involves inserting special instruments and a laparoscope through small incisions in the abdomen. The laparoscope is a long thin camera that sends pictures of the inside of your body to a video screen viewed by your surgeon during the surgery. Minimally invasive surgery generally involves a faster recovery and less pain than open surgery. This is because it causes less trauma to tissues and organs. Your surgeon will make small incisions instead of a larger one used in open surgery. Surgical tools are threaded around muscles, tissues, and organs instead of cutting through or displacing them as in open surgery.

  • Open surgery involves making a long incision in your abdomen. Open surgery allows your surgeon to view and access the surgical area directly. Open surgery generally involves a longer recovery and more pain than minimally invasive surgery. Open surgery requires a larger incision and more cutting and displacement of muscle and other tissues than minimally invasive surgery. Despite this, open surgery may be a safer or more effective method for some patients, such as those who are very obese or have adhesions (scarring from previous surgeries).

Minimally invasive techniques may be combined with an open surgery in some cases. Additionally, your surgeon may decide after beginning a minimally invasive technique that you need open surgery to complete your surgery safely.
Your surgeon will advise you on which procedure is best for you and how long you need to stay in the hospital based on your diagnosis, age, medical history, general health, and possibly your personal preference. Learn about the different gastric bypass surgeries and ask why your surgeon will use a particular type for you.

Types of anesthesia that may be used

General anesthesia is used for gastric bypass. General anesthesia is a combination of intravenous (IV) medications and gases that put you in a deep sleep. You are unaware of the procedure and do not feel pain

What to expect the day of your gastric bypass

The day of your surgery, you can generally expect to:

  • Talk with a preoperative nurse. The nurse will perform an exam and ensure that all needed tests are in order. The nurse can also answer questions and will make sure you understand and sign the surgical consent form.

  • Remove all clothing and jewelry and dress in a hospital gown. It is a good idea to leave all jewelry and valuables at home or with a family member if possible. Your care team will give you blankets for modesty and warmth.

  • Talk with the anesthesiologist or nurse anesthetist about your medical history and the type of anesthesia you will have.   

  • A surgical team member will start an IV.

  • The anesthesiologist or nurse anesthetist will start your anesthesia.

  • A tube will be placed in your windpipe to protect and control breathing during general anesthesia. You will not feel or remember this or the surgery as they happen.

  • The surgical team will monitor your vital signs and other critical body functions. This occurs throughout surgery and recovery until you are alert, breathing effectively, and vital signs are stable.

What are the risks and potential complications of gastric bypass?  

As with all surgeries, gastric bypass involves risks and the possible complications. Complications may become serious and life threatening in some cases. Complications can develop during surgery or recovery.

General risks of surgery 

The general risks of surgery include: 

  • Anesthesia reaction, such as an allergic reaction and problems with breathing 

  • Bleeding or hemorrhage (heavy bleeding), which can lead to shock

  • Blood clot, in particular a deep vein thrombosis that develops in the leg or pelvis

  • Infection

Potential complications of gastric bypass

Complications of gastric bypass include:

  • Constipation

  • Damage to abdominal organs or major blood vessels

  • Dehydration

  • Difficulty swallowing (dysphagia)

  • Dumping syndrome (rapid emptying of stomach contents into the small intestine causing symptoms, such as nausea, vomiting, cramping, and abdominal pain)

  • Gallstones

  • Gastritis (irritated stomach tissue), ulcers, gastroesophageal reflux (regurgitation), and heartburn 

  • Hernias 

  • Intestinal stricture (narrowing) 

  • Leaking of digested foods and digestive juices into the abdominal cavity from the area where organs are sewed together 

  • Malnutrition including vitamin and mineral deficiencies. This can lead to long-term complications, such as osteoporosis, anemia, and permanent nervous system damage

  • Nausea, vomiting, gas and bloating

  • Poor weight loss results or inability to maintain long-term weight loss 

Reducing your risk of complications

You can reduce the risk of certain complications by following your treatment plan and:

  • Following activity, dietary and lifestyle restrictions and recommendations 

  • Notifying your doctor right away of any concerns, such as bleeding, fever, increase in pain, or wound redness, swelling or drainage 

  • Taking your medications and vitamin and mineral supplements exactly as directed

  • Telling all members of your care team if you have any allergies 

How do I prepare for gastric bypass? 

You are an important member of your own healthcare team. The steps you take before surgery can improve your comfort and outcome.

You can prepare for a gastric bypass by:

  • Answering all questions about your medical history and medications. This includes prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times.

  • Getting preoperative testing as directed. Testing will vary depending on your age, health, and specific procedure. Preoperative testing may include a chest X-ray, electrocardiography (ECG), blood tests, and other tests as needed.

  • Losing some weight as directed by your surgeon. Even losing a small amount of weight can help reduce serious risks of gastric bypass surgery.

  • Not eating or drinking before surgery as directed. Your surgery may be cancelled if you eat or drink too close to the start of surgery because you can choke on stomach contents during anesthesia.

  • Stopping smoking as soon as possible. Even quitting for just a few days can be beneficial and help the healing process.

  • Taking or stopping medications exactly as directed. This may include not taking aspirin, ibuprofen (Advil, Motrin), and blood thinners. Your doctor will give you instructions for taking your specific medications and supplements.

Questions to ask your doctor

Facing surgery can be stressful. It is common for patients to forget some of their questions during a doctor’s office visit. You may also think of other questions after your appointment. Contact your doctor with concerns and questions before gastric bypass and between appointments.  

It is also a good idea to bring a list of questions to your appointments. Questions can include:

  • Why do I need gastric bypass? Are there any other options for treating my condition?

  • How long will the procedure take? When can I go home?

  • What restrictions will I have after the surgery? When can I return to work and other activities?

  • What kind of assistance will I need at home?

  • How should I take my medications? 

  • How will you treat my pain?

  • When should I follow up with you?

  • How should I contact you if problems arise? Ask for numbers to call during and after regular hours. 

What can I expect after gastric bypass?

Knowing what to expect can help make your road to recovery after gastric bypass surgery as smooth as possible.

How long will it take to recover?

You will stay in the recovery room after surgery until you are alert, breathing effectively, and all vital signs are stable. You may have a sore throat if a tube was placed in your windpipe during surgery. This is usually temporary, but tell your care team if you are uncomfortable.

You may have a tube that was passed through your nose into your stomach during surgery. This tube will be used to keep your stomach empty. Your surgeon will remove the tube when your stomach has recovered enough from the effects of surgery to work properly. The tube is generally taken out within 24 hours. 

You will stay in the hospital three to five days. Full recovery is a gradual process. Recovery times vary depending on the procedure, your general health, age, and other factors. Full recovery takes four to six weeks. 

Will I feel pain?

Pain control is important for healing and a smooth recovery. There will be discomfort after your surgery. Your surgeon will treat your pain so you are comfortable and can get the rest you need. Call your doctor if your pain gets worse or changes in any way because it may be a sign of a complication.

You will likely have narcotics for the pain. Narcotics will make you feel drowsy. You should not drive while taking this medication. 

When should I call my doctor?

It is important to keep your follow-up appointments after gastric bypass. Contact your doctor for questions and concerns between appointments. Call your surgeon right away or seek immediate medical care if you have:

  • Breathing problems, such as shortness of breath, difficulty breathing, labored breathing, or wheezing

  • Change in alertness, such as passing out, unresponsiveness, or confusion

  • Chest pain, chest tightness, chest pressure, or palpitations

  • Fever. A low-grade fever (lower than 101 degrees Fahrenheit) is common for a couple of days after surgery and not necessarily a sign of a surgical infection. However, you should follow your doctor's specific instructions about when to call for a fever.

  • Inability to urinate or have a bowel movement

  • Leg pain, redness or swelling, especially in the calf, which may indicate a blood clot

  • Nausea and vomiting

  • Pain that is not controlled by your pain medication or severe abdominal pain

  • Uncontrolled or heavy bleeding (hemorrhage)

  • Unexpected drainage, pus, redness or swelling of your incision

How might gastric bypass affect my everyday life?

Gastric bypass is not a quick or easy fix for obesity. It is only one part of a complete obesity treatment plan. A complete plan includes a lifelong commitment to healthy dietary and exercise habits, vitamin supplementation, and regular follow-up care. 

Gastric bypass generally helps people to successfully lose weight, but there are risks. Risk include vitamin and mineral deficiencies that require ongoing supplementation. Left untreated, vitamin and mineral deficiencies can lead to long-term complications, such as osteoporosis and anemia.

Your diet will change drastically after gastric bypass. Your surgeon will give you specific instructions about your diet and activity restrictions. Diets after gastric bypass generally start with very small amounts of liquids and then progress to small amounts of pureed and soft foods. You will slowly transition to solid foods about 10 to 12 weeks after surgery.

Gastric bypass can also cause other significant changes that may affect your everyday life including:

  • Change of body image

  • Changes in social, work and family relationships. As you lose weight, you will probably have an increase in energy and ability to participate in everyday activities, sports, exercise, social activities, and work.

  • Chronic diarrhea may occur in some cases

  • Decreased risk of heart disease and its complications 

  • Improved quality of life

  • Improvement or resolution of many diseases and conditions. These include migraines, depression, type 2 diabetes, metabolic syndrome, polycystic ovarian syndrome, venous stasis disease, gastroesophageal reflux disease (GERD), hypertension, stress urinary incontinence, gout, and high cholesterol.

  • Decreased need for medications that treat chronic conditions related to obesity. You will need to see your primary care provider regularly to adjust your medications.

Was this helpful?
  1. Bariatric Surgery. The Journal of the American Medical Association.
  2. Bariatric Surgery - Following Doctor's Orders Results In 35% More Weight Loss. Medical News Today.
  3. Bariatric Surgery for Severe Obesity. National Institute of Diabetes and Digestive and Kidney diseases (NIDDK).
  4. Benefits of Bariatric Surgery. American Society for Metabolic & Bariatric Surgery.
  5. Pile, JC. Evaluating postoperative fever: A focused approach. Cleveland Clinic Journal of Medicine. 2006;73 (Suppl 1):S62.
  6. Poirier P, et al. Bariatric Surgery and Cardiovascular Risk Factors: A Scientific Statement from the American Heart Association. Circulation. 2011; 123: 1683-1701. Weight Loss Surgery.
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Oct 30
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