Gastric bypass surgery is used to treat severe obesity when techniques such as dietary changes, exercise and other methods have failed to control a patient’s weight. It is the most popular form of weight loss surgery (bariatric surgery) performed in the United States.

This type of surgery typically is performed on patients with a body mass index (BMI) of 40 or more. This measure is a calculation of a person’s height and weight, and a BMI of 40 represents a man who is about 100 pounds overweight, or a woman who is about 80 pounds overweight.

During a gastric bypass procedure, a patient’s digestive anatomy is surgically altered to restrict the amount of food they are physically able to eat at one time. In addition, the digestive tract is altered so that food bypasses part of the stomach and part of the small intestine, resulting in fewer calories being absorbed by the body.

Gastric bypass surgery is performed using general anesthesia, which means the patient is asleep during the procedure and does not feel pain. Gastric bypass can be performed as either traditional open surgery or as less invasive laparoscopy. The latter technique requires smaller incisions and generally has a shorter recovery time than the traditional technique.

Following surgery, patients are placed on a special diet that lasts for several months and progresses from liquids to pureed foods and soft foods. Eventually the patient will be allowed to eat solid foods. However, the changes to the digestive system brought on by surgery result in permanent restrictions on how much patients are able to eat and what kinds of food they can eat.

Gastric bypass surgery is the most commonly performed type of weight loss surgery (bariatric surgery) in the United States. This surgery alters the patient’s digestive anatomy to restrict the amount of food they are physically able to eat at one time. This promotes weight loss by causing the patient to feel full more quickly. The procedure also involves a bypass of part of the stomach and part of the small intestine that results in fewer calories being absorbed by the body.

Physicians generally encourage patients to lose weight through dietary modifications and lifestyle changes, including regular exercise. There are also a few medications that promote short-term weight loss. Bariatric surgery is considered only when these interventions prove insufficient to bring a severely obese patient’s weight to a healthy level. This type of surgery typically is performed on patients with a body mass index (BMI) of 40 or more. BMI is a measure of a person’s height and weight, and a BMI of 40 represents a man who is about 100 pounds overweight, or a woman who is about 80 pounds overweight. A normal BMI is somewhere between 18.5 and 25.

The digestive process begins as soon as a person swallows food. Once the food enters the digestive tract, digestive juices and enzymes digest food and help with the absorption of calories and nutrients. The food moves down the esophagus and into the stomach, where acid continues to digest the food. In the average person, the stomach can hold about 32 ounces (946 milliliters) of food at one time.

As this food is digested, it moves to the first part of the small intestine (known as the duodenum), where bile and pancreatic juices facilitate digestion and absorption. Most of the remaining calories and nutrients are absorbed in the final two segments of the small intestine (jejunum and ileum). Any remaining food moves into the large intestine before it is eliminated from the body.

Bariatric surgery techniques promote weight loss in one of two ways: either by restricting food intake or by interrupting the digestive process. Some procedures (e.g., gastric bypass) combine stomach restriction with partial bypass of the small intestine. Gastric bypass is often the preferred form of weight loss surgery because it is considered to be safer and to have fewer complications than other alternatives.

In this procedure, also known as Roux-en-Y gastric bypass (RGB), the surgeon first creates a small stomach pouch that serves to restrict food intake. A Y-shaped section of the small intestine is attached to the pouch. This allows food to bypass the lower stomach, the duodenum and the first portion of the jejunum, reducing the amount of calories and nutrients the body absorbs.

Gastric bypass can be performed as either traditional open surgery or as less invasive laparoscopy. In the latter technique, a small, tubular instrument called a laparoscope is inserted through a short incision in the abdomen. The laparoscope has a camera at the end that allows the physician to view the interior of the body. Surgical instruments are then passed through other short incisions to complete the surgery.

Patients who undergo the laparoscopic technique usually require a shorter hospital stay than those who undergo open surgery. In addition, laparoscopy usually requires a shorter recovery period, and presents a lesser risk of wound-related complications. However, people who weigh more than 350 pounds (158 kilograms) or have a history of abdominal surgery may not be good candidates for laparoscopy.

Only certain people are considered to be good candidates for gastric bypass surgery, such as those with a BMI of 40 or greater. Physicians may also permit gastric bypass for patients with a BMI of 35 to 39.9 who also have weight-related health problems such as diabetes, heart disease, severe sleep apnea (cessation of breathing during sleep) or high blood pressure (hypertension).

A team of health professionals (e.g., physicians, surgeons, dietitians, psychologists) will work together to help determine if a patient is a good candidate for bariatric surgery. Factors to be considered include potential benefits to a patient’s health, potential risks involved in the surgery and whether or not the patient can comply with the lifestyle changes necessary to ensure that the weight stays off following surgery.

The evaluation will include a thorough physical examination. The patient's medical history will be obtained, including a current list of medications and supplements. Blood tests and imaging tests (e.g., EKG, chest x-ray, upper gastrointestinal x-ray, gallbladder ultrasound) may also be performed.

Patients with certain preexisting conditions (e.g., alcoholism, hepatic cirrhosis with impaired liver function) may not be good candidates. Individuals with correctable hormonal causes of obesity may also not qualify.

A psychologist may help determine if a patient is able and willing to make the dietary and lifestyle adjustments necessary to ensure that the weight stays off, and to reduce the risk of complications. Patients with certain serious psychiatric conditions may be ruled out.

Gastric bypass surgery takes place in a hospital. Prior to the surgery, patients should follow all preparatory steps recommended by their physician. These may include modifications to diet, engaging in an exercise program and limiting or stopping use of alcohol and nicotine products. Patients may also be asked to refrain from taking certain medications, such as anticoagulants (e.g., aspirin) which inhibit the ability of the blood to clot. Fasting will also be necessary on the day of the procedure.

Patients are placed under general anesthesia, which means they are not awake for the procedure and feel no pain. A tube is inserted through the nose and into the upper stomach and connected to a suction machine, which will help in the healing process following surgery.

During the procedure, the stomach is made smaller by dividing it into a smaller upper section and a larger lower section. The surgeon uses surgical staples to seal off the upper part of the stomach from the remainder of the stomach. This creates a small pouch at the top of the stomach that is about the size of a walnut and is able to hold about 1 ounce (30 milliliters) of food.

The surgeon then cuts the small intestine and sews part of it onto the pouch. This arrangement allows food to bypass most of the stomach and the first section of the small intestine, known as the duodenum. Instead, the food travels from the surgically created pouch through the new connection (known as a Roux limb) and directly into the second segment of the small intestine, known as the jejunum. This limits the amount of calories absorbed into the body.

In rare cases, the gallbladder may also be removed (cholecystectomy) during a gastric bypass to prevent formation of gallstones that sometimes result from rapid weight loss. However, this is more often achieved through medications that dissolve these stones.

Gastric bypass surgery usually takes about four hours to complete. The incisions will be closed with stitches or surgical staples and then covered with a sterile bandage. The patient will have the stitches or staples removed at a later time during a follow up visit.

Following surgery, the patient will awaken in a recovery room and will be monitored for any post-surgery complications. Patients are typically required to remain in the hospital for three to five days. The tube that was inserted through the nose into the upper stomach before the procedure will help keep the new stomach pouch empty so that the staple line can heal. In some cases, a second tube will have been inserted into the bypassed stomach during surgery. This tube is usually removed four to six weeks after surgery.

Pain medication will be administered as needed, either intravenously or orally. Patients will be encouraged to move around as much as possible while in the bed, and ultimately to get up and walk around as they recover. It may take several weeks before a patient displays the same level of stamina they exhibited before the procedure.   

Patients typically cannot eat solid foods for a day or two after surgery. Once their stomach has had some time to heal, patients will be placed on a special diet. This will last for several months and begins with two to three days of clear liquids (e.g., water, juice, broth), followed by three or four weeks of thicker liquids (e.g., pudding, cream soups) and pureed foods (which have the consistency of a smooth paste) and then eight weeks of soft foods (e.g., finely diced meats, canned fruits, cooked vegetables).

Eventually, patients return to eating some regular foods, avoiding those that are high in fats and sugar. Patients will initially find that they need to eat very small meals through the day, although the stomach will stretch a bit over time. Gastric bypass patients must also drink plenty of liquids, but liquids cannot be consumed at mealtimes because the stomach is so small. For the first six months following surgery, patients often find that they may vomit or feel pain under the breastbone if they eat too much or eat too fast.

Aching may also occur at the incision site and within the abdominal muscles, particularly with deep breathing, coughing or exertion. In general, patients should refrain from strenuous activity, such as lifting heavy items, for several months after surgery to prevent strain on the abdominal muscles and incision site.

Patients may experience other signs and symptoms during this period as well, including:

• Nausea
• Body aches
• Feeling of tiredness similar to flu
• Feeling cold
• Dry skin
• Hair thinning or hair loss
• Mood changes
• Changes in bowel movements
• Constipation
• Loss of muscle mass

Patients should contact their physician if they experience any of the following:

• Fever
• Chills
• Redness or swelling at the incision site
• Bleeding or other drainage from the incision site
• Increased pain at the incision site

Physicians monitor gastric bypass patients closely for several years after surgery. Continued attention to weight loss and diet is essential for a successful outcome, and the patient is likely to consult with a registered dietitian or other dietary expert in planning appropriate meals. Patients may participate in support groups or use other methods to help adjust to their new lifestyle.

As people lose weight over the next one to two years they may develop excess skin. These patients may benefit from plastic surgery aimed at correcting the condition.

Patients who have gastric bypass surgery often lose more weight, lose weight more quickly and keep more weight off for longer periods of time than those who have other forms of bariatric surgery. However, individual results depend on many factors, including the type of procedure performed and the commitment of the patient to making the necessary dietary and lifestyle adjustments. Age, gender and initial weight at the time of the surgery may also play a role in the outcome.

Patients often report higher self-esteem and better general health, including having more endurance to carry out daily tasks. Gastric bypass surgery may also lengthen a patient’s lifespan and help improve symptoms of conditions related to obesity, including:

• Gastroesophageal reflux disease (GERD)
• Type 2 diabetes
• High cholesterol
• High blood pressure (hypertension)
• Obstructive sleep apnea (breathing cessation caused by enlarged tonsils)

Even when patients fail to reach their ideal weight, these medical conditions are usually improved following surgery.

Although gastric bypass surgery can create many health benefits for patients, it also includes some serious health risks. Patients are at risk for complications associated with all surgeries, such as infection or allergy to anesthesia.

Gastric bypass procedures are more difficult to perform than some other forms of bariatric surgery and are more likely to cause long-term nutritional deficiencies, particularly in regard to iron and calcium. This means that menstruating women are more likely to develop anemia. Osteoporosis and other bone diseases may result from calcium deficiency. Recent research also shows that nutritional deficiencies related to gastric bypass surgery may result in serious neurological conditions. To guard against nutritional deficiencies, patients may be given nutritional supplements such as a multivitamin, vitamin B-12 and minerals such as calcium and iron.

Patients who have gastric bypass surgery may also suffer from dumping syndrome, which occurs when a meal high in simple carbohydrates moves too quickly through the small intestine, leading to nausea, bloating, abdominal pain, weakness, sweating, faintness and diarrhea. Patients may also develop an infection such as peritonitis, in addition to abdominal hernia, dehydration, gallstones or stomach ulcer. Research also shows that patients may be at increased risk of developing kidney stones following gastric bypass surgery. Some of these complications may require additional surgery.

Other risks associated with bariatric surgery include:

• Death. Patients have died as a result of these surgeries. Risk levels vary depending upon a person’s age, general health and other medical conditions. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the risk of death from gastric bypass surgery is less than 1 percent.
  
  
• Blood clots in the legs. These clots may form in the legs before traveling to the lungs and into the arteries found there. This can cause a pulmonary embolism, which can be fatal. Walking and wearing leg wraps can reduce this risk. Leg exercises may also be recommended.
  
  
• Leaking from a staple line. This severe complication is usually treated with antibiotics, and some cases may require emergency surgery.
  
  
• Narrowed opening connecting the stomach and small intestine. This complication is rare and often can be corrected by an outpatient procedure in which a tube (endoscope) is inserted through the mouth to widen the opening. In some cases, corrective surgery may be necessary.
  
  
• Pneumonia. Patients may have a higher risk of this disease after surgery.

The changes to the digestive system brought on by surgery result in permanent restrictions on how much patients are able to eat and what kinds of food they may eat. Although the average stomach can hold 32 ounces (946 milliliters) of food, a stomach that has undergone gastric bypass surgery holds only 4 to 8 ounces (118 to 236 milliliters) of thoroughly chewed food.  Eating too much food can result in pain, nausea, vomiting, abdominal cramps, bloating and diarrhea.

The dietary restrictions required after gastric bypass surgery may present problems for some patients. Most postsurgical diet problems are caused by foods high in fats and sugars, which may have represented a large part of the diet that caused patients to gain weight before surgery. Following surgery, patients will likely be urged to eat foods that are high in protein and low in fat, fiber, calories and sugar.

Patients must learn to eat and drink extremely slowly, taking at least 30 minutes to consume a meal and 30 to 60 minutes to drink a cup of liquid. Chewing food thoroughly can help prevent blockages that can otherwise form at the new opening from the stomach to the intestine.

By eating and drinking small amounts slowly, patients can also reduce the risk of dumping syndrome, which occurs when a meal high in simple carbohydrates moves too quickly through the small intestine, leading to nausea, bloating, abdominal pain, weakness, sweating, faintness and diarrhea. This is especially important when consuming high-sugar foods and drinks, such as ice cream and soda. Drinking beverages between meals rather than with them can reduce the risk of dumping syndrome and other symptoms.

Patients may lose as much as 50 to 60 percent of their excess weight within the first two years after surgery. However, there is no guarantee that patients will keep the weight off over the long term. A healthy diet, regular exercise and making other physician-prescribed lifestyle changes will increase a patient’s chances of maintaining a healthy weight level.

It is important to note that women should not become pregnant in the first year following the surgery. The rapid weight loss associated with gastric bypass can pose a risk to the fetus.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to gastric bypass:

1. Am I a good candidate for gastric bypass surgery?
   
   
2. What form of gastric bypass surgery to you recommend for me and why?
   
   
3. Can you explain the procedure to me in detail?
   
   
4. What are the risks associated with gastric bypass surgery?
   
   
5. How long will it be before I can eat solid foods following surgery?
   
   
6. How will my long-term eating habits change following gastric bypass surgery?
   
   
7. How can I avoid nutritional deficiencies that are sometimes associated with gastric bypass surgery?
   
   
8. How much weight might I lose? Is there a chance I will gain back the weight later?
   
   
9. How can I increase my chances of keeping off the excess weight?
   
   
10. How many gastric bypass procedures have you performed?
    
    
11. What complications have you seen in your surgical patients?
    
    
12. What type of follow-up care do you provide?