How it works to help you lose weight
The gastric bypass surgical technique, which limits food and keeps it from being absorbed completely, is the most frequently performed bariatric and metabolic procedure in the United States. This technique alters the complex relationship your body has with food and its metabolism. This positive change helps reset your body’s ability to effectively manage weight. The surgery allows the body to establish a new, lower, healthier body fat set point.

  • The surgeon creates a stomach pouch that significantly reduces overall stomach size and the amount of food it can hold.

  • The pouch is surgically attached to the middle of the small intestine, thereby bypassing the rest of the stomach and the upper portion of the small intestine (duodenum).

  • The smaller stomach size helps patients feel full more quickly, which reduces food intake.

  • Bypassing part of the intestine limits calorie absorption.

  • Gastric bypass also produces positive metabolic changes in many organs as a result of surgical anatomic manipulation.

The procedure
The surgeon creates a small stomach pouch using staples, then attaches a section of the small intestine directly to the pouch. The remaining stomach area is stapled shut and divided from the smaller pouch. This allows food to bypass a portion of the small intestine where calories and nutrients are normally absorbed.


  • Limits the amount of food that can be eaten at a meal and reduces the desire to eat.

  • Allows the body to adjust to its new, healthier set point.

  • Average excess weight loss is generally higher than with gastric banding or sleeve gastrectomy.

  • No postoperative adjustments are required.

  • An analysis of clinical studies reported an average excess weight loss of 62% in 4204 patients.

  • Shown to help resolve type 2 diabetes (68%), high blood pressure (66%), obstructive
    sleep apnea (76%), and to help improve high cholesterol (95%).

  • In a study of 608 gastric bypass patients, 553 maintained contact for 14 years; the study reported that significant weight loss was maintained at 14 years.


  • Because the duodenum is bypassed, poor absorption of iron and calcium can result in the lowering of total body iron and a predisposition to iron deficiency anemia. Women should be aware of the potential for heightened bone calcium loss.

  • 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 managed through proper diet and vitamin supplements.

  • Chronic anemia due to vitamin B12 deficiency can occur. This can usually be managed with vitamin B12 pills or injections.

  • When removing or bypassing the pylorus, 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 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.

  • In some cases, the effectiveness of the procedure may be reduced if the stomach pouch is stretched and/or if it is initially left larger than 15cc to 30cc.

  • Rerouting of bile, pancreatic and other digestive juices beyond the stomach can cause intestinal irritation and ulcers.

  • The lower stomach pouch 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.


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