After gastric bypass, large stomach pouches and diabetes make weight loss less effective

After gastric bypass, large stomach pouches and diabetes make weight loss less effective

When individuals have diabetes or have larger stomach pouches, they are less likely to successfully lose weight after gastric bypass surgery, according to an article released on September 15, 2008 in the Archives of Surgery, one of the JAMA/Archives journals.

The most common bariatric procedure in North Amrica is the Rout-en-Y gastric bypass surgery, according to the article. The procedure entails the surgical creation of a smaller stomach pouch, in order to restrict food intake and bypass sections of the digestive system.

However, the authors point out that, while the bypass surgery is often effective, there can be some complications. "When performed in high-volume centers and with a low rate of complications, gastric bypass provides sustained and meaningful weight loss, significant improvement in quality of life, improvement or resolution of obesity-associated comorbidities and extended life span,"write the authors. "However, 5 percent to 15 percent of patients do not lose weight successfully, despite perceived precise surgical technique and regular follow-up."

To investigate this phenomenon, Guilherme M. Campos, M.D., and colleagues at the University of California, San Francisco examined data taken about 361 gastric bypass recipients at one medical institution between 2003 and 2006. Follow-up was performed for 12 months on 310 of the patients, and poor weight loss was defined as losing 40% or less of one's excess body weight at the end of this follow-up. Those showing good weight loss were able to lose more than 40% of this excess body weight.

Before surgery, the subjects' average BMI was 34, and they lost an average of 60% of their excess body weight. In total, 38 of these patients showed poor weight loss. Adjusting for other factors, there were two that independently associated with poor weight loss: a larger stomach pouch size and the presence of diabetes.

There are several biological reasons that could lead to this oucome in diabetics. For instance, diabetes patients may take insulin or other medications that stimulate fat and cholesterol production. The authors point out that diabetes may additionally result be changes in eating habits: "Other factors that may lead to weight gain in patients with diabetes include a 'protective' increase in caloric intake to treat episodes of hypoglycemia [low blood sugar], reduction of urinary glucose losses and sodium and water retention that are a direct effect of insulin on the distal tubule in the kidney."

Regarding the size of the stomach pouch, the authors note that gastic bypass surgery is not well standardized. According to surveys, surgeons estimate the size of the pouch rather than using a balloon for sizing. This parameter may be extremely important, as the restricted dietary intake that the surgery hopes to impose is caused by the decreased stomach pouch side. "As the use of gastric bypass continues to grow, we believe it is critical to stress the importance of and to teach the creation of the small gastric pouch and to better standardize the technique used for pouch creation," write the authors.

The authors conclude that this procedure can be very effective for many patients but must be refined for better effectiveness in all patients. "We conclude that gastric bypass provides good or excellent weight loss for most patients," they say. "However, diabetes mellitus and larger pouch size are independently associated with poor weight loss after gastric bypass. Changes in the use of diabetes medications may reduce the risk of poor weight loss among diabetics undergoing gastric bypass. Detailed attention to the creation of a small gastric pouch is essential for achieving the best results."

Factors Associated With Weight Loss After Gastric Bypass

Guilherme M. Campos; Charlotte Rabl; Kathleen Mulligan; Andrew Posselt; Stanley J. Rogers; Antonio C. Westphalen; Feng Lin; Eric Vittinghoff

Arch Surg. 2008;143(9):877-884.

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