The scales are formally shifting on Body Mass Index, a measurement that has been the source of much scorn in recent years. The American Medical Association has now weighed in to say that doctors should look at factors beyond BMI to determine whether a patient is unhealthily obese.
Finally, medical science is looking beyond this nearly 200-year-old formula. It was devised not by a doctor, but by an astronomer. He used it to define what was “normal” — a normal based on White, 19th-century European men.
Now comes the tricky part: Shifting the way doctors and society define a healthy size — and ensuring people trying to lose weight can get the interventions they need.
BMI is someone’s weight in kilograms divided by the square of their height in meters. That mathematical approach has been used to stigmatize and even misdiagnose a swath of the population. It’s meant a skewed view of our nation’s health. And it has meant slapping an “overweight” or “obese” label on some people who are perfectly healthy, while overlooking others whose BMI is considered normal, but could use better guidance on exercising or eating healthy foods.
Everyone has had personal experiences that illustrate the problems with BMI. I still can’t shake the visceral reaction I had some years ago when a pediatrician began talking about her concerns about my kindergartner’s BMI. My daughter had stepped on the scale at the end of a summer where she treated mastering the monkey bars as her full-time job. The kid was ripped. Could the doctor not see that?
Yet pediatricians have leaned on BMI more and more over the years. A survey published last year found that by 2017, 95% of pediatricians were calculating BMI for their patients over the age of 2, compared to less than 40% of doctors in 2006. Many schools even added the measurement to report cards, despite no evidence that it influenced children’s weight.
Doctors’ time and energy would be better spent on other approaches to improving our nation’s health. As the AMA guidelines reiterate, BMI shouldn’t be looked at in isolation. The data are murky around when BMI is and is not an indicator of someone’s chances of developing diseases like diabetes and heart disease, or their risk of dying younger.
That doesn’t mean those health risks don’t exist, but it does mean that doctors should be using BMI alongside a more comprehensive list of health indicators. They should consider things like someone’s waist circumference, genetic risks for disease, body composition and their amount of visceral fat, or the fat that sits not just beneath the skin, but behind your muscles (people with an apple rather than pear shape typically have more visceral fat). The AMA’s new position should help shift the conversations between doctors and their patients.
But we do need to consider that releasing ourselves from the confines of the dreaded calculation could also further complicate people’s ability to access interventions. BMI is often used as a cutoff for access to certain treatments, and we can’t allow it to get even harder for people to access care they want and need, whether that’s weight-loss drugs like Ozempic and Wegovy, bariatric surgery or behavioral interventions. Indeed, the AMA also stressed that given differences in body shapes and fat distribution across people of different races, ages and genders, “BMI should not be used as a sole criterion to deny appropriate insurance reimbursement.”
Given the increasing prevalence of obesity and the projected astronomical cost to the economy (with the caveat that these numbers are calculated based on BMI!), it makes perfect sense for doctors to discuss healthy habits. But the conversation should be focused on health, not math.
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(Lisa Jarvis is a Bloomberg Opinion columnist covering biotech, health care and the pharmaceutical industry. Previously, she was executive editor of Chemical & Engineering News)
