Gastric bypass tied to better metabolic outcomes

Last Updated: 2017-04-19

By Marilynn Larkin

NEW YORK (Reuters Health) - Roux-en-Y gastric bypass is associated with greater metabolic improvements, independent of weight loss, than adjustable gastric banding, researchers in France say.

Although both gastric bypass and gastric banding restrict the stomach, gastric bypass “alters the physiology of the retained and bypassed parts of the small intestine,” which may explain why studies have shown greater weight loss following bypass, according to the authors.

To investigate whether the interventions confer improvements in glucose control beyond weight loss alone, Dr. Brandon Kayser of the Institute of Cardiometabolism and Nutrition in Paris and colleagues conducted lipidomic analyses, analyzing fasting sera from obese women (mean age, 36; body mass index, 37 to 51) who underwent the procedures.

Specifically, they looked at circulating phospholipids and sphingolipids (fatty acid derivatives of sphingosine that occur mainly in the cell membranes of central nervous system tissue), which are lipid markers implicated in obesity-related comorbidities such as insulin resistance and cardiovascular disease.

Sera were available before surgery from 37 women who underwent bypass and 22 who underwent banding; at one month after surgery, from 21 women who had gastric bypass and 12, banding; and at three months followup, from 19 who had gastric bypass and 12, banding.

Both procedures induced weight loss and improved clinical profiles, the team reports in the International Journal of Obesity, online April 4.

However, gastric bypass produced greater improvements in certain parameters. For example, gastric bypass patients went from a mean BMI of 46.5 at baseline to 38.3 post-surgery, whereas BMI in gastric banding patients decreased from 43.6 to 38.3.

At three-month follow-up, the percent fat mass decreased by 3.4% with gastric bypass and 2.4% with banding. Serum total cholesterol, low-density lipoprotein-cholesterol (LDL-C) and orosomucoid also showed greater improvements with gastric bypass (false discovery rate less than 10%).

Ninety-three of 131 lipids were affected by surgery, with the majority decreasing. A total of 29 lipids were differentially affected by gastric bypass, and the differences remained statistically significant for 20 of these lipids after adjustment for differences in weight loss between surgery types.

“The most significant finding,” according to the authors, is that gastric bypass patients had decreases in a number of phosphatidylcholine, sphingomyelin and longer-chain ceramides species by one and three months after surgery, whereas most of these lipids returned to baseline within three months after gastric banding.

In addition, most of the gastric bypass-specific changes were independent of weight loss.

Dr. Yulia Zak, a bariatric surgeon at Mount Sinai Beth Israel Medical Center in New York City, told Reuters Health, “The lipids preferentially affected by the Roux-en-Y gastric bypass have been previously shown to be associated with coronary artery disease and nonalcoholic fatty liver disease.”

“Based on the results of this study, gastric bypass is likely a better bariatric procedure for obese patients with these conditions,” she said by email, “both because it leads to better weight loss and . . . may result in more favorable alterations in lipid metabolism.”

Dr. Zak added, “Only women were included in this study, with a relatively small sample size, which makes it difficult to generalize the results to the entire population.”

“It is also unclear whether this is a long- or short-term effect, as the authors measured lipid levels only up to three months post-operatively,” she noted. “Further research will have to examine whether these differences persist after the patients’ weight stabilizes.”

Dr. Jon Schram, Medical Director, Bariatric Surgery at Spectrum Health in Zeeland, Michigan, told Reuters Health by email, “This study further validates previous research that has shown that the metabolic effects of gastric bypass and sleeve gastrectomy have a dramatic and measurable impact on type 2 diabetes, hypertension, and hyperlipidemia, making these the operations of choice for patients with morbid obesity.”

Dr. Michael Russo, a bariatric surgery specialist at MemorialCare Center for Obesity at Orange Coast Memorial Medical Center in Fountain Valley, California, added, “A large reason the gastric band has fallen out of favor is that it does not induce many of these changes on a hormonal level and therefore has less effect.”

The study “further emphasizes the metabolic benefits of gastric bypass,” he told Reuters Health by email, “and solidifies the national trend of offering the gastric sleeve and gastric bypass in favor of the band.”

The authors did not reply to requests for a comment.

SOURCE: http://bit.ly/2pChUxw

Int J Obesity 2017.