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Weight Loss & Bariatric Surgery

Gastric Bypass

Roux-en-Y Gastric Bypass (RNY)

Gastric Bypass

The Roux-en-Y Gastric Bypass – often called gastric bypass – is considered the ‘gold standard’ of weight loss surgery.

The Procedure

There are two components to the procedure. First, a small stomach pouch, approximately one ounce or 30 milliliters in volume, is created by dividing the top of the stomach from the rest of the stomach. Next, the first portion of the small intestine is divided, and the bottom end of the divided small intestine is brought up and connected to the newly created small stomach pouch. The procedure is completed by connecting the top portion of the divided small intestine to the small intestine further down so that the stomach acids and digestive enzymes from the bypassed stomach and first portion of small intestine will eventually mix with the food.

The gastric bypass works by several mechanisms. First, similar to most bariatric procedures, the newly created stomach pouch is considerably smaller and facilitates significantly smaller meals, which translates into fewer calories consumed. Additionally, because there is less digestion of food by the smaller stomach pouch, and there is a segment of small intestine that would normally absorb calories as well as nutrients that no longer has food going through it, there is less absorption of calories and nutrients.

Most importantly, the re-routing of the food stream produces changes in gut hormones that promote satiety, suppress hunger, and reverse one of the primary mechanisms by which obesity induces type 2 diabetes.


Gastric bypass produces significant long-term weight loss (60 to 80 percent of excess weight) by restricting the amount of food that can be consumed, and by limited the absorption of some calories and nutrients. It has been shown to result in favorable changes in gut hormones that reduce appetite and enhance satiety. Typically, patients of this procedure will maintain a 50 percent weight loss long term.


It is technically more complex than the Sleeve Gastrectomy and has the potential for greater complication rates. Due to the mal-absorptive element, it can cause long-term vitamin/mineral deficiencies, particularly deficits in vitamin B12, iron, calcium, and folate. This procedure requires strict adherence to dietary recommendations, life-long vitamin/mineral supplementation, and a commitment to follow-up compliance