Diabetes and Weight-loss Surgery

Diabetes is better cut-off for weight-loss surgery than body mass index (BMI)

Although obese women are the most common recipients of weight-loss (bariatric) surgery, men—particularly those with diabetes and who smoke—are at highest risk for mortality risk from obesity and may be the best candidates for surgery, according to a study published online ahead of print in JAMA Surgery. Diabetes, in particular, was linked to the highest risk for mortality from obesity.

“If we have to decide who should get the surgery first, it should be based on who has the highest risk of mortality,” said co-author Arya Sharma, MD, PhD, Professor of Medicine and Chair in Obesity Research and Management at the University of Alberta, Edmonton, Canada. “We looked at thousands of patient files and many different parameters, and surprisingly enough it came down to three things—if you’re male, you’re a smoker, and you have diabetes, you have the highest risk,” he said.

“If you’re a female non-smoker without diabetes—which, incidentally, is who is being operated on in general around the world—you have the lowest risk,” Dr. Sharma said. “Bariatric surgery is most often offered to younger, female non-smokers who don’t have diabetes,” he added.

Large-Scale Trial

The researchers examined data from 15,394 obese patients (ages 18 to 65 years) with a body mass index (BMI) of ≥35.0 alone or 30.0-34.9 with an obesity-related comorbidity. The patients were enrolled in the United Kingdom General Practice Research Database.

The all-cause mortality rate was 2.1%. The strongest risk factors for mortality were age (odds ratios [ORs], 1.09 per year) and type 2 diabetes (OR, 2.25) followed by smoking (OR, 1.62) and male gender (ORs, 1.50). BMI was the weakest predictor of mortality (OR, 1.03 per unit) of the factors included in this study.

Simple Tool to Calculate Mortality Risk Created

The researchers used the data to establish a simple 4-variable prediction rule for 10-year mortality from all causes based on age, sex, smoking, and diabetes mellitus. They noted that further research is needed to further delineate risk thresholds and to validate the findings. 

“These surgeries are being done, but are the wrong people getting them? The current BMI cut-off is missing the boat on those who need it most. Having diabetes is more important than BMI as a risk factor,” Dr. Sharma said. “Our research showed BMI didn’t really matter—so size alone isn’t a good way to decide who should get the surgery,” he said.

BMI Does Not Account For Age, Fitness Level, or Ethnicity

While BMI is an excellent tool for epidemiological studies, it does not always tell the whole story, said Walter Pories, MD, Professor of Surgery and Director of the Bariatric Surgery Research Group at the Brody School of Medicine, East Carolina University (ECU), Greenville, North Carolina. BMI does not account for fitness level, fails to recognize the differences in adiposity between the genders, and overlooks the increased adiposity that comes with aging, Dr. Pories told DiabeticLifestyle.com

“Most serious, however, is the discriminatory effect when imposed as a gateway to surgery. At similar levels of BMI, Asians and African American women are significantly more likely to be hypertensive and diabetic than Caucasians. To deny these racial groups the benefits of bariatric surgery based on a faulty metric is not justified,” Dr. Pories said.

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