Is BMI an Appropriate Qualifier for Bariatric Surgery?

Weight-loss (bariatric) surgery was found to be more effective than diet and exercise at controlling blood glucose for overweight patients with diabetes

Bariatric surgery was found to be more effective than nonsurgical interventions at controlling blood glucose for patients with diabetes at the low end of the obesity spectrum (body mass index [BMI], 30-35), according to a systemic review of short-term trials. However, the evidence in this population currently is insufficient to draw definite conclusions and larger, longer-term trials are needed, the authors noted in the June 5 issue of JAMA.

Use of BMI As a Cutoff Is Discriminatory, Expert Says

Use of surgery in patients with diabetes with a BMI <35 is controversial. While the FDA approved gastric banding for patients with a BMI of 30 to 40 and an obesity-related illness, the Centers for Medicare & Medicaid Services does not cover this procedure in patients with a BMI <35. 

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, argues that use of BMI as a cutoff for surgery in type 2 diabetes is discriminatory. He noted in an interview with DiabeticLifestyle.com that while the BMI (kg/m2) is an excellent tool for epidemiological studies, it does not always tell the whole story.

For example, “the BMI does not account for fitness,” he said, citing one of his volunteer subjects who met every requirement for bariatric surgery (5’8”; 307 lbs; BMI = 48.1), but “we couldn’t catch him; he was the fastest running back at ECU.” The unigender BMI also fails to recognize the differences in adiposity between the genders and overlooks the increased adiposity that comes with aging. “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.

Accordingly, Dr. Pories recommended that waist diameter, sagittal diameter, and severity of the comorbidities of obesity (eg, hypertension, diabetes, hyperlipidemia) would be far better measures for determining eligibility for bariatric surgery.

Beneficial Effects on Glucose Control in Non-Morbidly Obese
The current study review included 32 surgical studies, 11 systematic reviews of nonsurgical treatments, and 11 large nonsurgical studies published more recently than the systematic reviews, said lead author Melinda Maggard-Gibbons, MD, a surgeon at the David Geffen School of Medicine at the University of California, Los Angeles.

Of the 3 head-to-head studies included in the analysis, patients randomized to surgery had a greater weight loss (range, 14.4-24 kg) and glycemic control (range, 0.9-1.43 point improvements in hemoglobin A1c levels) over 1 to 2 years after surgery compared with patients who received nonsurgical treatment. Similar benefit was found in indirect comparisons of data from observational studies of bariatric procedures and meta-analyses of nonsurgical therapies at 1 to 2 years.

The findings “are something that surgeons who take care of these patients know because you see it anecdotally, but to bring the data together was really important,” said Dr. Maggard-Gibbons.

While long-term data on adverse events are needed, adverse events in the surgical group were low (eg, hospital deaths of 0.3%-1.0%). However, many of the studies enrolled a small number of patients and involved surgeries performed by a single surgeon at one academic institution. Thus, the data may not be applicable to other settings, according to the study authors.

How Is Surgical Success Defined?

Regarding the sustainability of the surgical approach to treatment, Dr. Maggard-Gibbons wondered, “Do we need to completely cure diabetes following surgery? Is it still beneficial if diabetes returns after a sustained period of time? Likewise, is achieving longstanding, but partial improvement still worthwhile? These discussions are critical to the debate on weighing the benefits to the risks.”

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