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Time to Rethink BMI Cutoff for Bariatric Surgery?

— The point isn't weight loss, researcher argues, but treatment for diabetes, hypertension, and other comorbidities

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LAS VEGAS -- Patients with BMI values below the usual eligibility threshold for bariatric surgery got significant benefits from the procedure, a researcher said here -- with weight loss perhaps the least important.

People with BMI under 35 -- the standard cutoff for severe obesity -- who underwent sleeve gastrectomy saw high resolution rates for several comorbidities, reported Oliver Varban, MD, of Michigan Medicine in Ann Arbor, at ObesityWeek 2019, the joint annual meeting of the Obesity Society and the American Society for Metabolic and Bariatric Surgery (ASMBS).

Compared with those with BMI of 35 or higher who underwent sleeve gastrectomy, patients with BMI under 35 on the day of surgery had similar rates for stopping several types of medication, indicating improvement or resolution of underlying conditions:

  • Hypertension medications: 59.7% for BMI <35 vs 54.1% for BMI ≥35
  • Hyperlipidemia medications: 54.3% vs 52.2%
  • Oral diabetes medications: 79.2% vs 78.1%
  • Insulin: 64.2% vs 62.2%
  • Proton pump inhibitors: 65.8% vs 68.9%

"We believe with this data we can start the conversation of changing some current guidelines for bariatric surgery to consider the focus to be more on metabolic disease, rather BMI alone as the only cutoff," Varban suggested during his oral presentation.

Another benefit of bariatric surgery that lower BMI patients experienced -- similar to that seen in conventional patients -- was improvement in quality of life. Nearly 90% of lower BMI patients said they were "very satisfied" with their quality of life, as did nearly 85% of higher BMI patients following surgery. Both BMI groups also had similar depression scores and psychological wellbeing scores subsequent to surgery.

Patients with lower BMI prior to surgery did have higher aggregate scores for body image versus the higher BMI patients, however (51% vs 43%).

As expected, patients with BMI under 35 at surgery, having less excess weight to lose, showed less weight loss 1 year after the procedures compared to standard patients:

  • Weight loss: 46 lbs for BMI <35 vs 78 lbs for BMI ≥35
  • Total body weight loss: 22% vs 27%

But with the lower BMI starting point, more of the BMI <35 group achieved normal weight (BMI <25) after surgery, at 36% vs 6% for the BMI ≥35 group.

For the study, Varban and colleagues analyzed records for some 46,000 patients who underwent primary sleeve gastrectomy at 43 teaching or non-teaching hospitals in Michigan from 2006 to 2018. These included more than 1,000 patients with BMI <35. Among the standard patients, mean BMI was 46.7.

Prior to surgery, those with BMI under 35 were significantly older (50.7 vs 45.4). Lower BMI patients also had significantly higher rates of comorbidities including diabetes (36.7% vs 30.9%), hypertension (54.2% vs 51.0%), hyperlipidemia (57.1% vs 44.8%), and reflux disease (55.7% vs 49.2%).

Similar 30-day risk-adjusted complication rates were seen in the low and high BMI groups, with total complication rate of 5.9% and 5.3%, respectively. Medical complications, surgical complications, rates of emergency department visits, readmission rates, extended length of stay, and mortality rate within 30 days of the operation also did not significantly differ between the groups.

Calling the study "fantastic," invited discussant Mona Misra, MD, of Cedars Sinai Medical Center in Los Angeles, asked about the best way to bring the option of bariatric surgery to patients with sub-35 BMI, observing that "it is challenging enough to even convince physicians to refer morbidly obese patients for these clearly much-needed and life-saving procedures."

Varban replied, "I think the way the messaging should be moving forward is not to call it weight loss surgery, not call it bariatric surgery, but call it surgery to treat specific conditions that we know it can -- things like diabetes, high blood pressure, hyperlipidemia, metabolic disease."

"I think the idea there will be to really reframe the conversation with the patient about what success looks like," he continued. "If they come to clinic and they want a certain amount of pounds to lose, that can certainly be a side effect of the operation, but really if they come to the clinic because they want to resolve their diabetes, then we have more and more data to show the likelihood of that happening."

"And that really is the endpoint we should look at with some of these operations."

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    Kristen Monaco is a senior staff writer, focusing on endocrinology, psychiatry, and nephrology news. Based out of the New York City office, she’s worked at the company since 2015.

Disclosures

Varban reported no disclosures.

Primary Source

ObesityWeek

Varban O, et al "Is it Worth it? Determining the Health Benefits of Sleeve Gastrectomy in Patients with a Body Mass Index Less than 35 kg/m2" ObesityWeek 2019; Abstract A105.