Diabetes Blunts Weight Loss Effect of Bariatric Surgery

Kari Oakes

April 02, 2020

People with diabetes may benefit less from bariatric surgery, compared with those without the disease, according to a retrospective review of patients receiving both sleeve gastrectomy and gastric bypass.

The difference was particularly pronounced and persistent for patients who had gastric bypass, Yingying Luo, MD, said during a virtual news conference held by the Endocrine Society. The study was slated for presentation during ENDO 2020, the society's annual meeting, which was canceled because of the COVID-19 pandemic.

"Our findings demonstrated that having bariatric surgery before developing diabetes may result in greater weight loss from the surgery, especially within the first 3 years after surgery and in patients undergoing gastric bypass surgery," said Dr. Luo.

More than a third of U.S. adults have obesity, and more than half the population is overweight or has obesity, said Dr. Luo, citing data from the Centers for Disease Control and Prevention.

Bariatric surgery not only reduces body weight, but also "can lead to remission of many metabolic disorders, including diabetes, hypertension, and dyslipidemia," said Dr. Luo, a visiting scholar at the University of Michigan's division of metabolism, endocrinology, and diabetes. However, until now, it has not been known how diabetes interacts with bariatric surgery to affect weight loss outcomes.

To address that question, Dr. Luo and her colleagues looked at patients in the Michigan Bariatric Surgery Cohort who were at least 18 years old and had a body mass index (BMI) of more than 40 kg/m2, or of more than 35 kg/m2 with comorbidities.

The researchers followed 380 patients who received gastric bypass and 334 who received sleeve gastrectomy for at least 5 years. Over time, sleeve gastrectomy became the predominant type of surgery conducted, noted Dr. Luo.

At baseline, and yearly for 5 years thereafter, the researchers recorded participants' BMI as well as their lipid levels and other laboratory values. Medication use was also tracked. Patients with a diagnosis of diabetes also had their hemoglobin A1c levels recorded at each visit.

Overall, patients in the sleeve gastrectomy group were more overweight, and those in the gastric bypass group had higher HbA1c and total cholesterol levels. The mean baseline weight for the sleeve gastrectomy recipients was 141.5 kg, compared with 133.5 kg for those receiving gastric bypass (BMI, 49.9 vs. 47.3 kg/m2, respectively; P < .01 for both measures). Mean HbA1c was 6.5% for the gastric bypass group, compared with 6.3% for the sleeve gastrectomy group (P = .03).

At baseline, 149 (39.2%) of the gastric bypass patients had diabetes, compared with 108 (32.3%) of the sleeve gastrectomy patients, but the difference was not statistically significant.

About two-thirds of the full cohort were tracked for at least 5 years, which is still considered "a good follow-up rate in a real-world study," said Dr. Luo.

Total weight loss was defined as the difference between initial weight and postoperative weight at a given point in time. Excess weight was the difference between initial weight and an individual's ideal weight, that is, what their weight would have been if they had a BMI of 25 kg/m2.

"The probability of achieving a BMI of less than 30 kg/m2 or excess weight loss of 50% or more was higher in patients who did not have diabetes diagnosis at baseline. We found that the presence of diabetes at baseline substantially impacted the probability of achieving both indicators," said Dr. Luo. "Individuals without diabetes had a 1.5 times higher chance of achieving a BMI of under 30 kg/m2, and...[they also] had a 1.6 times higher chance of achieving excess body weight loss of 50%, or more." Both of those differences were statistically significant on univariate analysis (P = .0249 and .0021, respectively).

The researchers conducted further statistical analysis – adjusted for age, gender, surgery type, and baseline weight – to examine whether diabetes still predicted future weight loss after bariatric surgery. After those adjustments, they still found that “the presence of diabetes before surgery is an indicator of future weight loss outcomes,” said Dr. Luo.

The differences in outcomes for those with and without diabetes tended to diminish over time in looking at the cohort as a whole. However, greater BMI reduction for those without diabetes persisted for the full 5 years of follow-up for the gastric bypass recipients. Those trends held when the researchers looked at the proportion of patients whose BMI dropped to below 30 kg/m2, and those who achieved excess weight loss of more than 50%.

Dr. Luo acknowledged that an ideal study would track patients for longer than 5 years and that studies involving more patients would also be useful. Still, she said, "our study opens the door for further research to understand why diabetes diminishes the weight loss effect of bariatric surgery."

The research will be published in a special supplemental issue of the Journal of the Endocrine Society. In addition to a series of news conferences on March 30-31, the society will host ENDO Online 2020 during June 8-22, which will present programming for clinicians and researchers.

Dr. Luo reported no outside sources of funding and no conflicts of interest.

SOURCE: Luo Y et al. ENDO 2020, Abstract 590.

This story originally appeared on MDedge.com.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.