A gastric bypass procedure (GBP) or Roux-en-Y is any operation in which the stomach is divided into two sections: a small upper pouch and a much larger lower portion. This prevents the person from eating large portions of food since the upper pouch is very small and can only hold a small amount at the time. This surgery is different from the lap banding surgery.

Next, a small portion of the intestine is connected to the small stomach pouch, limiting the body’s ability to absorb calories. The Roux-en-Y surgery is named after the French doctor Roux who first did it and it is restrictive and malabsorptive.

Gastric bypass procedure – The Roux-en-Y gastric bypass

According to the American Society for Bariatric Surgery and the National Institutes of Health, the most common weight loss surgery performed in the U.S. is the Roux-en-Y gastric bypass which is considered the gold standard procedure for weight loss surgery.

The surgery is performed by non-too invasive techniques named “laparoscopy”. Laparoscopic surgery is performed using several small incisions. A surgical telescope connected to a video camera allows the surgeon to view his operation on a video screen.

The Laparoscopic Gastric Bypass, Roux-en-Y was first performed in 1993. It basically consists on:

Dividing the stomach in two parts with staples, making the upper pouch very small to restrict the volume of food which the person can eat.
Re-constructing the gastrointestinal tract to allow both parts of the stomach to drain. This technique has several variations based on the length of the intestine used.

Variations of gastric bypass Roux en Y

Roux-en-Y – Proximal

This variant is by far the most commonly bariatric surgery performed in the United States and is the operation which is least likely to result in nutritional difficulties. The small bowel is divided about 18 inches (45 cm) below the lower stomach outlet, and is re-arranged into a Y-configuration, to allow the passage of food from the small upper stomach pouch, via a “Roux limb”.In the proximal version, the Y-intersection is formed near the upper (proximal) end of the small bowel. The Roux limb is constructed with a length of 31 to 59 inches (80 to 150 cm), preserving most of the small bowel for absorption of nutrients.

Roux-en-Y – Distal

Here the Y-connection is placed farther down in the intestine which reduces the amount of bowel necessary to absorb nutrients. This procedure causes malabsorption primarily of fat and starches, but also various vitamins and minerals.The Y-connection is formed much closer to the lower (distal) end of the small bowel, usually 100 to 150 cm (39 to 59 in) from the lower end of the bowel, causing reduced absorption (mal-absorption) of food, primarily of fats and starches, but also of various minerals, and the fat-soluble vitamins.The unabsorbed fats and starches pass into the large intestine, where bacterial actions may act on them to produce irritants and malodorous gases. These increasing nutritional effects are traded for a relatively modest increase in total weight loss.

Loop Gastric bypass – Mini gastric bypass

The Mini-Gastric Bypass, which uses the loop reconstruction, has been suggested as an alternative to the Roux en-Y procedure, due to the simplicity of its construction, which reduced the challenge of laparoscopic surgery.


Any major surgery involves the potential for complications, including mortality. Some complications are common to all abdominal operations, while some are specific to bariatric surgery. A person who chooses to undergo bariatric surgery should know about these risks:

Mortality is affected by complications caused by risk factors that existed before surgery such as diabetes, heart disease, the degree of obesity and sleep apnea. Mortality is also affected by the experience of the surgeon who operates. If you are considering this type of surgery make sure you do your research and ask for references.
Other complications can be due to the release of bacteria from the bowel during the operation. Possible infections include pneumonia, bladder or kidney infections or sepsis (infection of the blood).
Hemorrhage due to the cutting of blood vessels in order to divide the stomach and move the bowel.
An internal hernia may result from surgery and re-arrangement of the bowel although with laparoscopic surgery this risk is very much decreased.
Bowel obstruction.
Formation of blood clots, mainly in the legs. A clot can travel to the lungs and cause a pulmonary embolus, a very dangerous occurrence.
Nutritional deficiencies due to poor absorption of calcium and iron. Calcium and iron are mainly absorbed in the duodenum, a part of the intestine that is bypassed by the surgery. The patient needs to supplement these two minerals.
Deficiencies of zinc, vitamin B1 and B12 which leads to anemia.
Protein malnutrition. Restriction of protein intake will cause a loss of muscle mass resulting in weakness in the months following surgery.
Depression. This is a result of a change in the role food plays in the emotional well-being of the patient; strict limitations on the type and amount of food allowed can place great emotional strain on the person.
Some of these complications will require a second surgery.

Benefits of gastric bypass procedure

Patients who undergo Roux-en-Y surgery typically lose about 65 to 80% of their excess body weight. A dramatic reduction of he following health conditions is also achieved:

Hyperlipidemia (high cholesterol and high triglycerides levels) is corrected in over 70% of patients.
Essential hypertension is reduced in over 70% of patients, and medication requirements are usually reduced in the remainder.
Sleep apnea improves substantially in most patients.
Diabetes type 2 is reversed in up to 90% of patients usually leading to a normal blood sugar without medication, sometimes within days of surgery.
Low back pain and joint pain are typically relieved or improved in nearly all patients.
Patients are able to enjoy greater social participation.
What you can expect from an Roux-en-Y surgery as far as losing weight

On average, after this type of surgery, patients lose about 60 to 75 percent of their excess weight. So, let us say you are 100 pounds overweight, you will lose about 60 to 75 pounds. If you are highly motivated in the diet and exercise department, you can lose even more. The opposite is also true: if you are not sufficiently committed to exercise and eating healthier, you may lose less.

Final words

The first months following the surgery can be very difficult, an issue not often mentioned by physicians suggesting the surgery. The benefits and risks of this surgery are well established; however, the psychological effects are not well understood, and potential patients should ensure a strong support system before agreeing to the procedure. It is important for patients to start changing their outlook on food and diets before surgery to avoid the shock after.


I am Andy Carpenter and I would start by saying that I have a Bachelor Degree in Nutrition Science conferred by California State University, Los Angeles and that I am certified as a Registered Dietitian.

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