People who seek medical treatment for obesity or an eating disorder do so with the hope their health plan will pay for part of it. But whether it’s covered often comes down to a measure invented almost 200 years ago by a Belgian mathematician as part of his quest to use statistics to define the “average man.”
What is BMI?
That work, done in the 1830s by Adolphe Quetelet, appealed to life insurance companies, which created “ideal” weight tables after the turn of the century. By the 1970s and 1980s, the measurement, now dubbed body mass index, was adopted to screen for and track obesity.
Now it’s everywhere, using an equation — essentially a ratio of mass to height — to categorize patients as overweight, underweight, or at a “healthy weight.” It’s appealingly simple, with a scale that designates adults who score between 18.5 and 24.9 as within a healthy range.
But critics — and they are widespread these days — say it was never meant as a health diagnostic tool. “BMI does not come from science or medicine,” says Dr. Fatima Stanford, an obesity medicine specialist and the equity director of the endocrine division at Massachusetts General Hospital.
She and other experts say BMI can be useful in tracking population-wide weight trends, but it falls short by failing to account for differences among ethnic groups, and it can target some people, including athletes, as overweight or obese because it does not distinguish between muscle mass and fat.
Still, BMI has become a standard tool to determine who is most at risk of the health consequences of excess weight — and who qualifies for often-expensive treatments. Despite the heavy debate surrounding BMI, the consensus is that people who are overweight or obese are at greater risk for a host of health problems, including diabetes, liver problems, osteoarthritis, high blood pressure, sleep apnea, and cardiovascular problems.
The BMI measure is commonly included in the prescribing directions for weight loss drugs. Some of the newest and most effective drugs, limit use to patients who have a BMI of 30 or higher — the obesity threshold — or a lower level of 27, if the patient has at least one weight-related medical condition, such as diabetes. Doctors can prescribe the medications to patients who don’t meet those label requirements, but insurers might not cover any of the cost.
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BMI and weight loss medications
While most insurers, including Medicare, cover some forms of bariatric surgery for weight loss, they might require a patient to have a BMI of at least 35, along with other health conditions, such as high blood pressure or diabetes, to qualify.
With medications, it can be even trickier. Medicare, for example, does not cover most prescription weight loss drugs, although it will cover behavioral health treatments and obesity screening. Coverage for weight loss medications varies among private health plans.
“It’s very frustrating because everything we do in obesity medicine is based on these cutoffs,” says Stanford.
Critics say that BMI can err on both ends of the scale, mistakenly labeling some larger people as unhealthy and people who weigh