Gastric Bypass Surgery: Overview

Gastric bypass weight loss surgery

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In This Article

Gastric bypass surgery, also known as Roux-en-Y gastric bypass surgery (RYGB), is a type of bariatric (weight loss) surgery. The surgery works by restricting the amount of food a person can eat, as well as limiting their gut absorption of nutrients. Learning everything you can about gastric bypass (if considering it) is a good idea. In addition to careful preparation, patients must be willing and able to make permanent lifestyle adjustments pertaining to diet and exercise after the surgery.

What Is Gastric Bypass Surgery?

Gastric bypass surgery is performed by a bariatric surgeon in a hospital or surgical center under general anesthesia. This scheduled surgery requires a two to five-day hospital stay and is performed in adults and occasionally, adolescents.

In gastric bypass surgery, the surgeon creates a small pouch (about the size of an egg) out of the patient's existing stomach. With a much smaller stomach, patients cannot eat as much food. The surgeon then connects the new stomach pouch to a lower part of the small intestines. By bypassing the upper part of the small intestines, fewer calories and nutrients are absorbed from any ingested food.

Various Surgical Techniques

In the majority of cases, gastric bypass is performed laparoscopically. This means that the surgeon uses long instruments to operate through tiny incisions. Less commonly, the surgery is performed as open surgery. This means that the surgeon accesses the stomach and small intestines through a large incision in the abdomen.

According to the American Society for Metabolic and Bariatric Surgery, gastric bypass is considered the "gold standard" of weight loss surgery. While a complex operation, when compared to other weight-loss surgeries—such as adjustable gastric banding and sleeve gastrectomy—gastric bypass is associated with a greater and more sustained weight loss.

Criteria and Contraindications

While there are multiple benefits associated with gastric bypass surgery, not everyone is a candidate. The indications for undergoing gastric bypass include a patient who:

Moreover, due to a higher prevalence of abdominal obesity, weight loss surgery may be considered for Asian patients who have uncontrolled type 2 diabetes and a BMI as low as 27.5. 

Relative contraindications to undergoing gastric bypass surgery include patients with the following medical conditions:

A patient undergoing treatment for cancer, as well as a patient who cannot undergo general anesthesia, are additional contraindications.

Potential Risks

Besides the risks that go along with any surgery—blood clots, pneumonia, or bleeding—some of the specific risks associated with gastric bypass surgery include:

  • Dumping syndrome: Dumping syndrome is a condition where food moves very quickly from the stomach into the small intestine. It may cause feelings of nausea, cold sweats, light-headedness, and often severe diarrhea.
  • Malnutrition: Various protein and vitamin/mineral deficiencies may occur since this surgery changes the body's ability to absorb nutrients.
  • Leakage: A gastrointestinal leak of digestive juices and partially digested food may occur either where the small intestines is connected to the stomach, or where it is connected to the lower end of itself.
  • Small bowel obstruction: An obstruction of the small bowel is most commonly caused by an internal hernia, which is when the bowel protrudes through a defect created surgically within the abdominal cavity.
  • Marginal ulcer formation: A marginal ulcer resembles a peptic ulcer. It is located near the site where the stomach pouch and small intestines are connected.
  • Gastrogastric fistula: This complication refers to an abnormal tract that forms between the new stomach pouch and the old stomach remnant.
  • Anastomotic stenosis: Sometimes the connection (called the anastomosis) between the stomach pouch and the small intestines narrows, which can eventually lead to a patient's inability to swallow liquids.

Purpose of Gastric Bypass Surgery

Weight loss is the primary purpose of gastric bypass surgery. With this weight loss comes the potential benefit of reversing or improving various obesity-related health conditions, such as:

Other possible benefits of gastric bypass include improved health-related quality of life and a reduction in all-cause mortality (death).

How to Prepare

Once your gastric bypass surgery is scheduled, your surgical team will give you instructions on how to prepare for the operation:

These instructions may include:

  • Stopping smoking several months prior to surgery.
  • Consuming a low-calorie diet for about two weeks prior to surgery (this reduces liver volume, which can help the surgeon during the operation).
  • Stopping certain medications for a period of time before surgery (for example, non-steroidal anti-inflammatory medications, or NSAIDs).
  • Not eating or drinking anything after midnight on the eve before surgery.
  • Packing personal items (e.g., toothbrush) for your hospital stay.

What to Expect on the Day of Surgery

On the day of your surgery, you can expect the following:

  • Upon arrival at the hospital, you will go to a pre-operative room where you will change into a hospital gown.
  • A nurse will place a small tube (an IV catheter) in a vein in your arm, and an antibiotic will be given.
  • You will be taken into an operating room and given medication to put you to sleep.
  • The surgeon will make multiple incisions in the upper abdomen through which various surgical instruments will be inserted (if performed laparoscopically).
  • Using these surgical instruments, the surgeon will create a 30-mL pouch from the area of the stomach closest to the esophagus. The pouch will be completely detached from the rest of the stomach, and the remaining stomach will be stapled closed.
  • Once the pouch is formed, an incision will be made in the small intestines, dividing it into an upper and lower section.
  • The upper part of the small intestines (called the duodenum) will be bypassed, while the lower part (called the jejunum) will be pulled up and connected to the newly formed pouch.
  • The end of the bypassed duodenum will then be re-connected to the jejunum to allow food and digestive enzymes to mix.
  • The incisions will then be closed with dissolvable sutures or surgical staples.
  • Anesthesia will be stopped and you will be taken to a recovery room.


While recovering in the hospital after gastric bypass surgery, your surgical team will monitor your vital signs carefully and help control common post-surgical symptoms like pain, nausea, and vomiting.

Your nurse will teach you breathing exercises, as well as how to open up your lungs using a device called an "incentive spirometer."

In addition, a physical therapist will come to visit you in your hospital room to teach you leg exercises. Your therapist will eventually help you get out of bed and walk around (usually by the first day after surgery).

Upon discharge, your surgeon will give you specific instructions about recovering at home. Some of these instructions may include:

  • Keeping the incision site(s) clean and dry.
  • Avoiding strenuous activities for three to six weeks after surgery.
  • Avoiding heavy lifting for three months after surgery.
  • Gradually increasing your activity every day (by six weeks, you should be walking two miles or more a day).
  • Drinking two liters of water a day by taking small, frequent sips.
  • Taking any medications as directed (all medications will need to be crushed, or taken in liquid or chewable forms for the first six months after surgery).

When to Seek Medical Attention

As you recover from surgery, it's important to reach out to your surgeon if you develop any of the following symptoms:

  • Fever
  • Signs of a wound infection (e.g., redness, swelling, increased pain, or abnormal drainage)
  • Chest pain or trouble breathing
  • Nausea or vomiting that lasts more than 12 hours
  • Leg or calf pain, redness, or swelling
  • Urinating fewer than four times in 24 hours
  • Pain that is not eased with medication

Long-Term Care

After laparoscopic gastric bypass surgery, 80% of patients lose more than 70% of their excess body weight over two years, and 70% achieve greater than 50% over three years.

The key to maintaining this weight loss in the long-term includes the following practices:

  • Adhering to a well-balanced diet
  • Ensuring proper hydration
  • Exercising regularly (30 minutes, five to seven days a week)
  • Taking your vitamin supplements as advised (complex multivitamin, calcium, vitamin D, iron, vitamin C, and vitamin B12)
  • Following specific meal guidelines (e.g., no liquids at meals and avoiding carbonated drinks)

It's also important to attend all of your follow-up appointments with your surgeon and bariatric dietician. The purpose of these various appointments is to:

  • Evaluate for and manage potential complications or symptoms related to the surgery (e.g., dumping syndrome, vomiting, and fatigue)
  • Monitor health conditions that now may have reversed or be improved (e.g., type 2 diabetes)
  • Keep track of your weight loss progress
  • Identify any emotional or psychological needs after the surgery

A Word From Verywell

Undergoing gastric bypass surgery is a lifelong decision. If you or a loved one is considering gastric bypass (or any weight loss surgery), remain diligent in gaining knowledge about this operation. Seek out opinions from trusted and well-qualified medical professionals, as well, to ensure the surgery is the right decision for you.

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