Encumbered by Obesity, BMI, and Medical Groupthink
The scientific understanding of obesity is progressing with impressive speed. But the translation of scientific insight into clinical benefits is slow by comparison. Most clinicians (along with the public) are stuck. We’re encumbered by an inadequate definition of obesity, overreliance on BMI, and medical groupthink.
Straining for a Clinical Definition
In an excellent essay for the New York Times, Julia Belluz describes the challenge of coming up with an adequate clinical definition for the disease of obesity. She even questions whether the present way clinicians define obesity is adequate for calling it a disease:
“The more I know about obesity, the more the D-word gives me pause. Excess fat is the defining characteristic of obesity, linked to sickness and death since antiquity. But modern science tells a more nuanced story. Excess fat can be a symptom of illness, a disease itself or a risk factor – an on-ramp – for other health problems. The ills of excess fat can manifest in people with larger bodies and high B.M.I.s, and in people who aren’t large at all but harbor abnormal body fat – what’s referred to as ‘normal weight obesity’ or ‘thin fat obesity.’”
Thus, Francesco Rubino is working with a Lancet commission to publish an objectively better clinical definition of obesity. He says the clinical definition of a disease should objective, not based on any purpose, no matter how good the intent might be:
“This is crucial because if one defines a disease inaccurately, everything that stems from there – from diagnosis to treatment to policies – will be distorted and biased.”
Down with BMI?
All of this leads to the very popular impulse to throw BMI (body mass index) onto the trash heap. It’s an old, imperfect measure cooked up by some old White guy and sometimes held to be racist, sexist, and a prime cause of weight bias. A recent paper in JAMA Network Open even suggests replacing it with the BRI – the body roundness index.
Diana Thomas, who first published on the BRI more than a decade ago, says this kind of thinking is flawed:
“Some of this conversation misses the point. That is, why are we using thresholds and indices? We need to be using all the data we have, including the clinician’s assessment. Three dimensional body shape is another assessment tool that has potential.
“People want it to be easy, but humans are complex.”
Medical Groupthink
Since forever, health professionals – as well as the public – have been stuck on a framework for understanding obesity exclusively in terms of diet and exercise. Calories in and calories out. Obesity scientists know better, but medical groupthink is resistant to change. This is the same phenomenon that made 19th-century physicians resistant to washing hands before delivering babies to prevent deaths from “childbed fever.” It led pediatricians to make peanut allergies more common by advising mothers to avoid exposing their infants to peanuts.
Just as medical groupthink harmed those women and infants, it has long harmed people living with obesity. But experience tells us that we can do this. We can indeed discard the flawed groupthink around obesity that favors simple answers and blame on diet and exercise.
It’s taking time. But adopting better options for obesity care, putting BMI into perspective, and actively resisting medical groupthink will move us ahead.
Click here for the Belluz essay, here for more on BMI, and here for perspective on medical groupthink.
Coiled Rope, photograph by Nevit Dilmen, licensed under CC BY-SA 3.0
Subscribe by email to follow the accumulating evidence and observations that shape our view of health, obesity, and policy.
September 22, 2024
