Understanding Gastric Bypass Weight Loss Surgery

Gastric bypass weight loss surgery

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Gastric bypass is a mixed weight loss surgery, utilizing both a decrease in stomach size and a partial bypass of the small intestine to limit calorie intake. Gastric bypass is also commonly referred to as "roux-en-y" weight loss surgery and is one of the most successful weight loss surgeries for sustained, long-term weight loss. 

Gastric bypass patients feel full much faster and stay that way much longer than is typical. This is because a pouch is created to isolate only a small section of the stomach for the processing of food. In addition, a section of the small intestine is bypassed to reduce the amount of food, and therefore calories, that can be used by the body.

If you undergo this procedure, you must make radical changes in your food intake and lifestyle in order for the procedure to have the maximum effect. Meals after surgery must be limited to approximately one ounce each; drinking fluids with meals can fill the pouch, too, so you should be mindful that doing so may prevent the intake of solid food. But, because the stomach has the ability to stretch to accommodate food, you can consume larger portions than that over time.

The Gastric Bypass Surgery Procedure

The gastric bypass surgery is typically performed in a hospital or a surgery center, using General Anesthesia. Most of the time, the procedure is performed laparoscopically, which means the surgeon uses long instruments to operate through tiny incisions. In rare cases, the surgery will be "Open," performed through a larger, traditional incision. A surgery that begins laparoscopically may also be converted to an open procedure if the surgeon determines it is necessary.

The surgeon makes multiple incisions in the upper abdomen. The instruments are inserted through these incisions, and the surgeon begins by creating a pouch from the area of the stomach closest to the esophagus. The pouch is completely detached from the rest of the stomach, which is stapled closed and remains in the body (although it will no longer digest food). The sphincter muscle, which holds food in the stomach, remains attached to the unused portion of the stomach; the upper stomach sphincter becomes the entrance to the pouch.

Once the pouch is formed, the small intestine remains attached to the portion of the stomach that does not process food. An incision dividing the small intestine into a lower and upper section is made, with the upper section being stapled closed. The lower section of the stomach is then attached to the newly made pouch. The upper part of the small intestine remains in the body, attached to the unused stomach, but it, too, no longer processes food.

After the surgeon determines that the staples and sutures do not leak, the instruments are withdrawn and the incisions are closed, typically with absorbable sutures and sterile tape.

The Typical Outcome of Gastric Bypass Surgery

This procedure is more successful than restrictive procedures, such as gastric banding, because it does not rely solely on behavior modification. While the pouch helps create a feeling of fullness and does not allow for large meals to be consumed, the calories that are consumed are not fully used by the body due to the bypass of part of the small intestine.

Because weight loss is not totally dependent upon the continuation of eating very small meals alone, patients typically lose at least 60% of their excess weight after surgery; over a third lose 80%. Most patients reach their lowest weight of about two years after surgery. One recent study showed that 90% of patients maintain a loss of half their original body weight ten years after having surgery, a result that has only been shown with Roux-en-Y and a similar surgery, biliopancreatic diversion. Unfortunately, the biliopancreatic diversion--and sometimes the roux-en-y--cause difficulties with obtaining adequate nutrition and absorbing enough vitamins and minerals.

Potential Drawbacks of Gastric Bypass Surgery

Of course, there are negatives to this, and any, procedure. Many patients experience dumping syndrome, a condition where food moves very quickly from the stomach into the small intestine, causing feelings of nausea, cold sweats, chills, and often severe diarrhea and chest pain. Most patients find that limiting meal size and sugar consumption prevents dumping syndrome.

Malnutrition is also a risk, as this procedure decreases the body's ability to absorb nutrients, and most patients need vitamin and mineral supplementation for the rest of their lives.

The surgery is not reversible, but the restrictive nature of the surgery can be eliminated by consistent overeating, which can stretch the pouch until the amount of food able to be digested and used by the body is far less restricted than intended by the surgeon. If you desire this change, speak with your doctor so you can devise a plan to help you do this comfortably and safely.

Overall, gastric bypass is the most commonly performed weight loss surgery, with 140,000 procedures performed in the United States annually. While it is a complex surgery with significant risks, patients have historically had better results with total weight loss, long-term weight maintenance and improved overall health than those who have opted for any other type of weight loss surgery.


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Article Sources
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  • Bariatric Surgery for Severe Obesity. Consumer Information Sheet. National Institute of Diabetes and Digestive and Kidney Diseases. March 2008.
  • Jones,NicolasV. Christou, MD,PhD, Didier Look, MD, and Lloyd D. MacLean, MD,PhD. Weight Gain After Short- and Long-Limb Gastric Bypass in Patients Followed for Longer Than 10 Years. Annals of Surgery2006 November; 244(5): 734–740.