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This procedure is considered the “gold standard” of weight loss surgery.  There are multiple steps in this procedure.  First, the stomach is divided, and a small stomach pouch, about the size of 2 small medicine cups (about 30 milliliters), is created.  Second, the first portion of the small intestine is then cut/divided.  The lower portion of the divided intestine is then brought up and attached to the small stomach pouch.  This allows food eaten to pass through the stomach pouch into the intestine.  The final step is completed by attaching the upper part of the divided small intestine to a portion of existing intestine lower down.  This upper portion of the intestine, also known as the duodenum, then empties stomach acids and other digestive enzymes from the unattached (bypassed) stomach into the intestine.  These fluids then mix with food and aid in digestion.  

Weight loss occurs following this procedure through several mechanisms.  First, it is known as a restrictive procedure.  This means that the small stomach pouch will only hold a tiny amount of food at any given time, thus reducing the number of calories consumed.  Secondly, it is known as a malabsorptive procedure.  This occurs because the first part of the small intestine (duodenum) and the main portion of the stomach are now being “bypassed.”  They no longer have access to the food and therefore cannot participate in absorbing macro and micronutrients, thus resulting in fewer calories being absorbed.  Finally, and most importantly, the procedure facilitates changes in hormones produced by the gut, which promote the reduction in appetite and improved glycemic control. This frequently results in a rapid reversal of Type 2 Diabetes, as well as improves other metabolic disorders.  


  • Results in significant weight loss (60-80% of excess weight).
  • Produces positive changes in gut hormones that lead to reduced appetite and increased energy expenditure.
  • May lead to complete remission of Type 2 Diabetes.
  • Long-term maintenance of weight loss is typical >50% of excess weight.  


  • Is a more complex operation than Sleeve Gastrectomy and may result in higher complication rates.
  • May lead to long-term complications with vitamin and nutritional deficiencies, due to lack of absorption in the bypassed portions of the stomach and small intestine.
  • Commonly results in a longer hospital stay.
  • Requires strict adherence to dietary modifications for the rest of one’s life.
  • Typically requires long-term vitamin and mineral supplementation.
  • May result in post-gastric bypass hypoglycemic episodes.
  • May result in increased absorption of alcohol, rapid onset and prolonged intoxication, chronic alcoholism, and alcohol toxicity.