Diseases & Conditions


Bariatric Surgery

Bariatric surgery alters the stomach, intestine, or both to produce weight loss.

In the United States, more than 200,000 people have bariatric surgery each year. This number accounts for almost two thirds of the total number of bariatric procedures done worldwide. These procedures result in substantial weight loss. People may lose half or even more of their excess weight and as much as 80 to 160 pounds. Weight loss is rapid at first, and then slows gradually over a period of about 2 years. Weight loss is often maintained for years. The loss greatly reduces the severity and risk of weight-related medical problems (such as high blood pressure and diabetes). It improves mood, self-esteem, body image, activity level, and ability to work and interact with other people.

When obesity is severe (BMI of more than 40), surgery is the treatment of choice. Surgery is also appropriate when people with a BMI of more than 35 have serious weight-related health problems, such as diabetes, high blood pressure, sleep apnea, or heart failure.

To qualify for surgery, people also need to do the following: Understand its risks and effects Be motivated to follow the changes in diet and lifestyle required after surgery Have tried other methods of losing weight Be physically and mentally able to undergo surgery

Whether bariatric surgery is appropriate for people younger than 18 or older than 65 is controversial.


Bariatric surgery is often done using a flexible viewing tube (laparoscope) inserted into a small incision (about 1 inch long) just below the navel. This technique is called laparoscopy. Four to six other surgical instruments are then inserted into the abdomen through similar small incisions. Whether laparoscopy can be used depends on the type of procedure and the person's size. If laparoscopy cannot be used, surgery involves a larger abdominal incision (called open abdominal surgery). Compared with open abdominal surgery, laparoscopy is much less invasive and recovery is much more rapid.

Bariatric surgery may restrict the amount of food people can eat, reduce the amount of food absorbed, or both.

Procedures That Restrict: These procedures include adjustable gastric banding and vertical banded gastroplasty. By restricting the amount of food that people can eat, these procedures make people feel “full” sooner.

Adjustable gastric banding can be done using a laparoscope. A band (sometimes called a lap band) is placed at the upper end of the stomach to divide the stomach into a small upper part and a larger lower part. Food passes through the band on its way to the intestine, but the band slows that passage. Connected to the band is a piece of tubing with a device that allows access at the other end (a port). The port is placed just under the skin so that the tightness of the band can be adjusted after surgery. Fluid can be injected through the port into the band to expand it and make the passageway through the stomach smaller. Or fluid can be removed from the band to shrink it and make the passageway larger. When the passageway is smaller, the upper part of the stomach fills more quickly, sending a message to the brain that the stomach is full. As a result, people eat smaller meals and lose substantial amounts of weight over time.

Banding the Stomach

For this procedure, an adjustable band is placed around the upper part of the stomach. It enables people to adjust the size of the passageway for food through the stomach.

After a small incision is made in the abdomen, a viewing tube (laparoscope) is inserted. While looking through the laparoscope, the surgeon places the band around the upper part of the stomach. On the inside of the band is an inflatable ring, which is connected to tubing with a small port at the other end. The port is placed just under the skin. A special needle can be inserted into the port through the skin. The needle is used to insert a salt water (saline) solution into the band or to remove it. Thus, the passageway can be made smaller or larger. When the passageway is smaller, the upper part of the stomach fills faster, causing people to feel “full” more quickly and thus eat less.

Vertical banded gastroplasty is no longer commonly done. For this procedure, staples are placed vertically down the stomach along about two thirds of its length. Thus, the top two thirds is divided, with one part smaller than the other. A nonadjustable plastic band is placed at the bottom of the staple line, where the divided parts of the stomach join. Food from the esophagus enters the smaller part, and the band restricts and thus delays the movement of food through the stomach. As a result, people cannot eat as much, and they feel full sooner.

Procedures That Reduce Absorption: These procedures include Roux-en-Y gastric bypass and biliopancreatic diversion with a duodenal switch. These procedures reroute food so that it bypasses parts of the stomach and small intestine, where it is normally absorbed. Thus, less food is absorbed. These procedures also restrict the movement of food through the digestive system.

Roux-en-Y gastric bypass accounts for most of the bariatric procedures in the United States, although banding is becoming more popular. Roux-en-Y gastric bypass can often be done through a laparoscope. The part of the stomach next to the esophagus is detached from the rest, creating a small pouch. As a result, the amount of food that can be eaten at one time is drastically reduced. A section of small intestine is used to connect the pouch to a lower part of the small intestine (this arrangement resembles a Y—hence the name). The opening between them is made narrow to further restrict the movement of food. This connection bypasses the lower part of the stomach and upper part of the small intestine, where much of the absorption occurs. However, it allows digestive juices (bile acids and pancreatic enzymes) to mix with the food. This mixing, which is necessary for food to be absorbed, enables vitamins and minerals to be digested and then absorbed and thus reduces the risk of nutritional deficiencies. Most people stay in the hospital overnight or longer.

For many people who have had a gastric bypass, eating foods high in fat and refined sugar can cause dumping syndrome. Symptoms include indigestion, nausea, diarrhea, abdominal pain, sweating, light-headedness, and weakness. Dumping syndrome occurs when undigested food from the stomach moves into the small intestine too quickly. This syndrome usually stops occurring after a short time.

Bypassing Part of the Digestive Tract

For this procedure, part of the stomach is detached from the rest, creating a small pouch. The pouch is connected to a lower part of the small intestine by a piece of small intestine—an arrangement that resembles a Y. As a result, parts of the stomach and small intestine are bypassed. However, digestive juices (bile acids and pancreatic enzymes) can still mix with food, enabling the body to absorb vitamins and minerals and reducing the risk of nutritional deficiencies.

Biliopancreatic diversion with a duodenal switch is rarely used. Part of the stomach is removed. In contrast to the Roux-en-Y bypass, the part of the stomach that is left connects normally to the esophagus and the small intestine. Also, the valve between the stomach and small intestine is left intact and can function normally. Thus, the stomach empties normally. The small intestine is divided. The part that connects with the stomach (duodenum) is cut and attached to the lower part (ileum), bypassing much of the small intestine. As a result, digestive juices (bile acids and pancreatic enzymes) cannot mix with food as well, and absorption is reduced. Nutritional deficiencies often result.


Before surgery, people are evaluated to determine whether they are able to withstand the stress of surgery. A physical examination and tests are done. Tests may include the following: Tests that are routinely done before surgery to check how well vital organs are functioning (see Surgery: Preparing for the Day of Surgery ) Blood tests, including liver function tests, blood sugar levels, and lipid levels (after fasting) Ultrasonography of the abdomen, including the gallbladder Echocardiography (ultrasonography of the heart) Pulmonary function tests Evaluation of the digestive tract (with ultrasonography or endoscopy) Thyroid function tests Sleep evaluation (including polysomnography) and testing for sleep apnea

Psychiatric and nutritional evaluations are also done. People should tell their doctor about any drugs or medicinal herbs they are taking. Some drugs, including anticoagulants (such as warfarin Some Trade Names COUMADIN ) and aspirin Some Trade Names ECOTRIN ASPERGUM , may be stopped before surgery.

After Surgery

After surgery, pain relievers are prescribed.

After Bariatric Surgery: When to Call the Doctor

After bariatric surgery, some symptoms are common and do not indicate a problem. However, the following symptoms require a call or visit to the doctor: Signs of infection at the incision site, such as redness, severe pain, swelling, a bad odor, or oozing Separation of stitched edges of the incision Continued or increasing abdominal pain Persistent fever or chills Vomiting Persistent bleeding Abnormal beating of the heart Diarrhea Dark, tarry, foul-smelling stools Shortness of breath Sweating Sudden paleness Persistent chest pain

For the first 2 weeks, the diet is liquids only. People are asked to drink small amounts frequently throughout the day. They should drink as much fluid as prescribed and should take a liquid protein supplement. For the next 2 weeks, people should consume a soft diet. After 4 weeks, they can start eating solid foods. The following can help people avoid digestive problems and discomfort: Taking small bites of food Chewing food thoroughly Avoiding high-fat and high-sugar foods, such as “fast food,” cakes, and cookies Eating only small amounts at each meal

Usually, people can resume taking their routine drugs after surgery, but tablets may have to be crushed.

People should start walking or doing leg exercises the day after surgery. To avoid blood clots, they should not stay in bed for long periods of time. They can return to their usual activities after about 1 week and to their usual exercises (such as aerobics and strength training) after a few weeks. They should consult their doctor before doing any heavy lifting and manual labor.

Possible Problems: Most people lose their appetite after surgery. People experience pain, and some have nausea and vomiting. Constipation is common. Drinking more fluids and not staying in bed too long at a time can help relieve constipation.

Serious complications, such as problems with the incision, infections, and lung problems, can occur after any operation (see Surgery: After Surgery ). In addition, the following complications can occur after bariatric surgery. However, when surgery is done at specialized centers, they occur in fewer than 10% of people. Most can be treated. Blockage of the intestine: In about 2 to 4% of people, the intestine becomes blocked because it becomes twisted or scar tissue forms. A blockage can develop weeks to months to years after surgery. Symptoms include severe abdominal pain, nausea, and vomiting. Leakage: In about 1% of people, the new connection between the stomach and intestine leaks. Leakage usually occurs within 2 weeks of surgery. As a result, the stomach's contents can leak into the abdominal cavity and cause a serious infection (peritonitis). Symptoms include a fast heart rate, abdominal pain, fever, shortness of breath, and a general sick feeling. Bleeding: Bleeding may occur at the connection between the stomach and intestine, elsewhere in the digestive tract, or in the abdominal cavity. People may vomit blood or have bloody diarrhea or dark, tarry stools. Gallstones: Many people who successfully follow a diet aimed at quick weight loss develop gallstones. To reduce this risk after bariatric surgery, people are given supplemental bile salts, but these supplements do not always prevent gallstones. About 7% of people who have bariatric surgery need to have their gallbladder removed later. Nutritional deficiencies: If people do not make a concentrated effort to eat enough protein, a protein deficiency may develop. Vitamins and minerals (such as vitamins B 12 and D, calcium, and iron) may not be absorbed as well after the surgery. Taking supplements, including a multivitamin, can help. Death: Up to 0.5% of people die after surgery. Usually, the cause is a blood clot that travels to the lungs or a severe infection from leakage of one of the connections in the stomach or intestines along with a preexisting heart or lung disorder. Risk is higher for older people and for people who have had open surgery, or who are very obese.

Follow Up: Visits to the doctor are scheduled every 4 to 6 weeks during the first several months after surgery—the time when weight loss is most rapid. Then visits are scheduled every 6 to 12 months. Weight and blood pressure are measured, and eating habits are discussed. People should report any problems they are having. Blood tests are done at each visit.

Last full review/revision August 2008 by Asish C. Sinha, MD, PhD

Source: The Merck Manual Home Edition