When Diets Fail: Bypass Surgery

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This is a continuation of yesterday’s piece titled “When Diets Fail”


Reduction/malabsorptive surgeries alter the way food flows through the intestines, sometimes forcing the food to bypass entire sections—which is why these procedures are sometimes called “gastric bypass.”

When a portion of your intestine is bypassed, some calories are lost in the feces accelerating the rate of weight loss. In addition, these types of surgery change the hormonal environment of the intestine. Levels of hormones such as GLP-1 and PPY are increased, which helps with insulin action and makes you feel full faster.

In a Roux-en-Y procedure, a small section of the stomach is separated from the rest of the organ and connected directly to the middle of the small intestine (a section called the jejunum).

When ingested, food will go straight from the esophagus, through the new tiny stomach, and into the jejunum, completely bypassing the duodenum (the first section of the intestine). The rest of the stomach and the bypassed duodenum are reconnected into the lowest portion of the small intestine to allow stomach contents to drain.

This procedure reduces stomach size over five-fold. One top of this smaller stomach size, patients who get this surgery lose more calories because there is less surface area to absorb the nutrients from the food passing through your system.

Also, because food never travels through the duodenum, that part of the intestine can’t absorb the calories and nutrients needed to create energy. This can lead to feelings of lethargy in patients who don’t follow the dietary modifications that follows the surgery.

The most complicated of the bariatric surgeries is also a mouthful—the Biliopancreatic diversion with duodenal switch. Only those with extremely high BMIs for whom no other procedure would work are eligible for this surgery, since the procedure also comes with the most potential complications.

As in the Roux-en-Y procedure, it induces weight loss through both calorie restriction and by nutrient malabsorption. While much of the stomach remains intact, the small intestine is divided into two sections. One section connects the lower third of the small intestine (called the ileum) to a short piece of the duodenum attached to the pyloric valve (the valve that lets broken-down food pass from the stomach through to the small intestine). The other end connects the pancreas and gall bladder to the large intestine.

This method effectively bypasses a large portion of the area where nutrients are absorbed.

Because such a large expanse of the intestine is circumvented, patients who elect this surgery experience greater nutrient deficiencies such as iron, calcium and B12 and have more side effects such as nausea, sweating, weakness and severe diarrhea after eating (especially after eating sugary foods) a condition known as dumping syndrome.

When parts of the bowel are circumvented like they are in these bypass surgeries, there is less opportunity for nutrients to be properly absorbed. Because of this possibility, patients of this procedure are required to follow a special high protein, low sugar diet that progress from liquids through soft solids to regular foods while taking several vitamin supplements.

Over time the rest of the intestines adapt and compensate for the missing sections. The stomach can also be stretched by eating large portions of food. Initially this will cause vomiting but if overeating continues, it is possible to regain the weight.

These surgeries are now being accepted as a mainstream way to control diabetes for people who are not responsive to medical management. Both the American Diabetes Association and the International Diabetes Federation both include these procedures as options for the obese.

And surgeons are always perfecting their craft. Although not available yet, newer procedures (with odd sounding names such as Transpyloric shuttles and Intragastric Balloons) are in the works and researchers are looking to find the lowest BMIs where the benefits outweigh the risks.

Visit us next Wednesday for a look at the complications and life style changes associated with these types of surgeries.

One Response to When Diets Fail: Bypass Surgery

  1. Pingback: Operation or Modification?: Weight Loss and Diabetes | Joslin Diabetes Center Blog

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