The Roux-en-Y gastric bypass remains the gold standard to which other weight loss operations are compared. It is one of the most frequently performed weight loss surgery procedures in the United States. The gastric bypass takes advantage of both restriction and malabsorption to work. The restrictive part of the procedure is the creation of the small stomach pouch with a very small outlet. The malabsorptive part of the procedure involves re-arranging of the small intestine to reduce how much of the intestine is involved in absorbing the small amount of food that is eaten.

The entire procedure is performed laparoscopically. The small stomach pouch is created by stapling. The pouch is created to be small – about 30cc in size. The remaining stomach is not removed, but simply stapled shut and separated from the stomach pouch. The small intestine is then rearranged - one cut end of the bowel is connected to the pouch, while the other cut end, is reconnected to the small bowel about 100 to 150cm from the pouch. The result is a "Y" shaped re-connection that gives the technique its name. The length of either segment of the intestine can be increased to produce lower or higher levels of malabsorption.

The operation restricts food intake very effectively, particularly during the first year, the time of maximum weight loss. Ultimately, a bypass patient will be able to eat about 4 ounces of food per meal 3 to 4 times a day while experiencing prolonged satisfaction and fullness from that small amount of food. Hunger and cravings are controlled, particularly if the patient is compliant with the rules. This is a profound experience for many, being released from a prison of hunger.

The average expected weight loss with the gastric bypass procedure is around 70% of excess weight. About 50% of the expected weight loss will be lost in the first 6 months after the operation. The remaining half is lost slower over the remaining half to one year. With good compliance, an 80% chance of maintaining the weight loss long-term can be expected, and 80% to 90% of patients have at least improvement and/or resolution of their medical problems.

Proceeding with weight loss surgery is a very personal and often difficult decision. Educating yourself about weight loss surgery is a very important first step. Although the information presented here may be very helpful, patients have repeatedly told us that attending the free weight loss surgery seminar played an important role in their education and decision-making.


Supplied by BMI Calculator USA

To be a candidate for any type of weight loss surgery, the individual must be severely (BMI > 35) or morbidly (BMI > 40) obese. Morbid obesity is usually defined as being about 100 pounds over your ideal body weight. A better way of defining morbid obesity is by using the Body Mass Index (BMI). BMI is a calculated number that takes weight and height into consideration. A person weighing 300 pounds who is 5ft tall will have a higher BMI than a person weighing 300 pounds but is 6ft tall.

To determine if you are severely or morbidly obese and thus potentially a candidate for the Roux-en-Y gastric bypass enter your height and weight into the BMI calculator.

Most insurance companies will have additional criteria to qualify for weight loss surgery. Below you will find the basic criteria most insurance companies use:

A Body Mass Index (BMI) > 40, regardless if medical problems or co-morbidities are present or not.

A Body Mass Index (BMI) > 35 and experiencing severe negative health effects or co-morbidities, such as high blood pressure, diabetes, and/or sleep apnea.


The gastric bypass operation is performed laparoscopically. Five small incisions are required to perform the operation. The first part of the operation is the creation of the small new stomach or “pouch”. With modern stapling devices, pouches are made as small as the size of your thumb. The pouch is created from the very top portion of your stomach and it is completely separated from your old stomach. The old stomach is not removed. It remains a viable organ, but it does not see food anymore. By leaving your old stomach inside, the bypass operation can be reversed if the need should arise.

Once the pouch is created, the second step is to perform the bypass. This means the intestine is rearranged to reduce the amount of intestine involved in absorbing food without removing any intestine. The point where the digestive enzymes mix with the food is delayed or moved further downstream. The point is approximately 100 cm from the pouch. To accomplish this the intestine is divided in one place and two connections need to be made to allow the digestive enzymes to meet with the food. The name Roux-en-Y gastric bypass comes from the way the anatomy appears when completed. The bowels are arranged in a Y shape, and approximately 150 cm of intestine are no longer involved in true digestion, or in other words, bypassed from food.


The bypass maintains the principles of restriction and malabsorption with metabolic effects. The small pouch and narrow outlet restrict food intake and maintain satiety, while the re-arranging of the small intestines allows for less digestion time. The combination of these two procedures results in additional weight loss compared to a restrictive operation alone, for example, the Lap-Band. Restriction remains the key to major weight loss.

The size of the pouch limits how much food you can eat, while the size of the outlet controls how quickly it can empty. The smaller the outlet, the longer it will take for food to leave the pouch. The longer the pouch is full, the longer you experience satiety and no hunger. Once the food exits the pouch into the small intestine, the malabsorptive component begins. By bypassing parts of the intestine, food is now delayed from mixing with the digestive enzymes. The food may not be digested completely and the food that is digested has less time to be absorbed because there is less bowel to absorb it. The digestion of food starts at a later point than normal. The point where the biliopancreatic limb is connected to the food conducting limb can vary to produce more or less malabsorption. More bypassed bowel increases risk and side-effects.

Surgery alone will not ensure long-term weight loss and disease management success. Surgery is a great tool to help patients do the work to reach their health and weight loss goals. The operation will help, and to a degree, force patients to change their eating habits and lifestyles. Patients are not able to eat normally anymore. This can be a profound experience for many, being released from a prison of hunger. The success in keeping the weight off strongly relies on patient education and compliance with the rules. Failure to follow these guidelines can defeat the purpose of the bypass. The amount of weight that you will lose will depend on how well the patient is using their tool or following the rules.

The rules are the key to success with all weight loss operations. Proper education and compliance with the rules are key to any patients success. The operation to a significant degree will force many patients to change their eating habits but we do not want patients to rely on that solely. The bypass is only a tool to help patients with the necessary work to reach their health and weight loss goals.


The medical and emotional benefits of the gastric bypass procedure begin almost immediately after surgery, and the cosmetic benefits follow their wake. Over time, the benefits of gastric bypass surgery may include:

  • Significant sustained weight loss

  • Blood sugar levels that become completely normal within one year of surgery

  • Lower or normal blood pressure

  • Lower or normal cholesterol levels

  • Lower dosages of medications

  • Relief from sleep apnea, acid reflux and urinary stress incontinence

  • Less arthritis pain and improved mobility

  • Increased energy and ability to exercise

  • Improved mood and self-esteem

  • Arrested progression of heart disease

  • Improvement of many lung conditions

  • Exercise endurance

  • The co-morbidities of clinically severe obesity begin to resolve before complete weight loss even occurs. Patients can expect:

  • Better control or cure of diabetes

  • Lowered or normalized blood pressure and cholesterol

  • Relief from sleep apnea, severe acid reflux, and urinary stress incontinence

  • Eased lower back, knee and hip pain

  • Enhanced mobility

  • Arrested or slowed progression of evolving heart disease

Your need for medications will decrease while your medical problems improve. With the bypass, patients lose around 2/3 of their excess weight within one and a half years. The average weight loss is 70% of excess weight. Half of that weight is lost in the first 6 months. In most patients, 80% are able to maintain their weight loss long-term. Some weight regain is common, approximately 10-15% after five years.


As with all surgery, there are risks. Patients considering surgery must weigh the risks and benefits of surgery against the severity of their obesity. The decision to proceed is based on the premise that the treatment should be less harmful than the disease being treated. Please read the obesity section of our website to learn about the disease, and the benefits weight loss surgery can offer to morbidly obese patients.

Complications can occur as with any type of surgery. Below is a list of some general and specific complications that are unique to the Roux-en-Y gastric bypass procedure:

  • Perforation/injury of stomach/intestine

  • Leakage from a connection or staple line causing infection

  • Spleen injury (requiring removal) and/or other injury to organ(s)

  • Gastric pouch outlet narrowing/stretching

  • Small bowel obstruction

  • Blood clots in legs

  • Pulmonary embolism (blood clot in the lung)

  • Inability to eat certain foods

  • Development of gallstones or gallbladder disease

  • Inflammation of pouch, pouch ulcer, marginal ulcer

  • Dumping syndrome - intolerance to refined sugar, possibly fat

  • Weight gain, failure to lose satisfactory weight

  • Instrumentation failure may or may not result in additional surgery

  • Pregnancy is not recommended during the first one and a half years of active weight loss

  • Other potential complications:

  • Anemia, vitamin/ mineral deficiency, protein malnutrition

Bypassing the duodenum can cause poor absorption of iron and calcium and result in lowering of total body iron and a predisposition to iron deficiency anemia. This is a particular concern for patients who experience chronic blood loss during excessive menstrual flow or bleeding hemorrhoids.

Women are already at risk for osteoporosis, particularly after menopause. Bypassing the duodenum has caused metabolic bone disease in some patients, resulting in bone pain, loss of height, humped back and fractures of the ribs and hip bones. All of the deficiencies mentioned above, however, can be easily prevented and managed through proper diet and vitamin supplements.

A chronic anemia due to Vitamin B12 deficiency may occur. The problem can usually be managed with Vitamin B12 pills or injections.

A condition known as "dumping syndrome " can occur as the result of rapid emptying of stomach contents into the small intestine. This is sometimes triggered when too much sugar or large amounts of sweet food are consumed. While generally not considered to be a serious risk to your health, the results can be extremely unpleasant and can include nausea, weakness, sweating, faintness and, on occasion, diarrhea after eating. Some patients are unable to eat any form of sweets after surgery. This is considered a beneficial side effect - it helps patients reduce sugar consumption.

The bypassed portion of the stomach, duodenum, and segments of the small intestine cannot be easily visualized using X-ray or endoscopy if problems such as ulcers, bleeding or malignancy should occur.

Operative mortality and morbidity: Operative (30-day) mortality for gastric bypass when performed by skilled surgeons is about 0.5%. Operative morbidity (e.g. pulmonary embolism, anastomotic leak, bleeding, wound infection) is about 5%. Compared with open procedures, the laparoscopic gastric bypass has a higher rate of intra-abdominal complications; whereas duration of hospitalization is shorter, wound complications are lower, and postoperative patient comfort is higher.

Long-term complications: gastric bypass can be associated with the dumping syndrome, stomal stenosis, marginal ulcers, staple line disruption, and internal hernias. Life-long oral or IM vitaminB12 supplementation, iron, vitamin B, folate, and calcium supplementation is recommended to avoid specific nutrient deficiency conditions, such as anemia. Ventral hernia formation is more prevalent after open gastric bypass than after the laparoscopic approach. A unique complication of gastric bypass is dilation of the bypassed distal stomach in the event of a small bowel obstruction, which can lead to rupture and death if not rapidly managed by distal gastric decompression.

Reversal and revision: gastric bypass can be functionally totally reversed, though this is rarely required. For all bariatric procedures, pure reversal without conversion to another bariatric procedure is almost certainly followed by a return to morbid obesity. A standard Roux-en-Y gastric bypass with failed weight loss can be revised to a very long-limb Roux-en-Y procedure.


  1. Produces significant long-term weight loss (60 to 80 percent excess weight loss) 

  2. Restricts the amount of food that can be consumed 

  3. May lead to conditions that increase energy expenditure 

  4. Produces favorable changes in gut hormones that reduce appetite and enhance satiety 

  5. Typical maintenance of >50% excess weight loss 


  1. Is technically a more complex operation than the AGB or LSG and potentially could result in greater complication rates 

  2. Can lead to long-term vitamin/mineral deficiencies particularly deficits in vitamin B12, iron, calcium, and folate 

  3. Generally has a longer hospital stay than the AGB 

  4. Requires adherence to dietary recommendations, life-long vitamin/mineral supplementation, and follow-up compliance 


The decision about which operation is best for you is a complicated one. The decision to proceed is based on the premise that the treatment should be less harmful than the disease being treated. Please read the obesity section of our website to learn about the disease, and the benefits weight loss surgery can offer to morbidly obese patients. Although the information presented throughout our website may be helpful, you will be able to learn substantially more about the benefits and risks of the Bypass operation during your visit with our bariatric surgeon at our free weight loss surgery seminar.