The American Medical Association’s recent warning against the use of body mass index may be a step in the right direction — but longtime critics of the metric worry it won’t fix bias in health care assessments.
It has been criticized for years because of its racist history, and many advocates and dietitians have questioned its effectiveness for Black Americans. They say the assumptions and treatment plans made by doctors based on BMI can have a harmful impact on Black folks who are otherwise healthy.
The index entered the medical field about 200 years ago by Adolphe Quetelet, a Belgian mathematician and statistician, who was looking to define the “normal man” using the Quetelet index that would eventually be used by Charles Davenport during the eugenics movement, said Sabrina Strings, an associate professor of sociology at the University of California, Irvine.
Then, starting in the 1970s, it was used to estimate body fat. The tool — which is weight in kilograms divided by height in meters squared — was ultimately renamed body mass index, or BMI. That number is then checked against thresholds, or “cut points.” A number of organizations used it to define obesity, including the World Health Organization and National Institutes of Health, and its use is widespread in the United States health care system.
The AMA’s new policy suggests using BMI with other measures, such as body composition, visceral fat levels and genetic or metabolic factors. The association did not propose to remove it completely from health assessments.
“I don’t treat to a target BMI or a target weight, ever,” said Dr. Fatima Cody Stanford, an obesity medicine and physician scientist at Massachusetts General Hospital. Instead, she looks at cholesterol, blood pressure, and insulin levels as well as liver function to determine the status of a patient’s health. “Health does not equal a particular size.”
Some experts say the recommendation is on par with how they’ve been using the metric for years. Others say medicine could go further in getting rid of the tool because of its racist history.
Capital B recently spoke separately with Strings, author of Fearing the Black Body: The Racial Origins of Fat Phobia, and Stanford, who teaches at Harvard University, about how BMI has caused harm and what the future of health care could look like. The conversation has been lightly edited for length and clarity.
In what ways do you think that BMI has been harmful or discriminatory?
STANFORD: When patients fixate on these numbers, it creates heightened anxiety, increased depression, and it may create disordered eating. A 74-year-old patient of mine underwent surgery and was using medications, but she wasn’t comfortable with the BMI number. Unfortunately, she started to restrict her eating. She told me she’d only been eating celery and onions for the last week because those were the lowest calorie foods. That is harmful. Yet her health parameters are phenomenal. It broke my heart.
STRINGS: When American doctors started to use it, they wanted to try to create these biomarkers, which are different classifications for determining what was so-called normal weight, underweight, or overweight. They conducted a very limited number of studies using almost exclusively white people. This should tell you just how problematic BMI is, especially for BIPOC people.
Black people, on average, tend to be heavier than white people, but we are frequently also healthier at the same weight. It could be because of slavery. We were bred to be bigger and stronger. We might have a higher muscle ratio — muscle to fat and muscle to lean tissue ratio — than other groups. The mechanisms behind this are not entirely clear. Medicine is relying on a white standard to tell Black people what we must weigh to be “healthy.”
Are there other metrics that clinicians should be using? What alternatives are there?
STANFORD: What I have always done with my patients is use weight status, and look at where that weight is carried. That tissue in the central region, which means in the abdominal region, is deleterious to our health. What I like about using something as simple as a tape measure is that it’s not cost prohibitive. We can use this in low-income environments, and we can use this in high-income environments. Some of the gold standard metrics and measures like a DEXA scan require a bit more time, and a lot more money. I see BMI as a screening tool, but not as a diagnostic tool. We’ve been using it as a diagnostic tool, which I think has been a significant error.
STRINGS: When I first saw this report about the AMA changing their guidelines, I was pretty excited. They are taking notice of contemporary researchers and contemporary activists’ work. Then, I looked closely at what they were proposing, and their solution was to put another tool on top of BMI. The solution to racism is to eradicate it. If the medical industry is serious about racism and its relationship to health outcomes — because we know that racism contributes to worse health outcomes for BIPOC folks and fat people — the solution would be to simply remove BMI.
We don’t actually need some other tools that can be used to stigmatize. We can have a holistic way of assessing health that does not rely on a one size standard.
Does this move by the American Medical Association create any real changes in practice?
STRINGS: I hope so, but it doesn’t mean that there aren’t still plenty of reports of people going to the doctor and the doctor telling them to lose weight immediately based on BMI. The doctor might exhibit various forms of fat bias. It means that fat people may not go back to the doctor, and that in itself could be harmful. Weight loss is a losing game, which is why the diet industry is a multibillion-dollar industry.
If I’m someone who’s looking at my own BMI, what should I do with that? How should we be thinking about BMI?
STANFORD: Do a deeper dive with a doctor to figure out what your overall health status looks like. BMI doesn’t tell us what the health status is. Do we have evidence of diabetes, hypertension, high blood pressure? Take all of these things together to determine what would be an appropriate treatment strategy. If there has been some weight gain, what is this associated with? Is it something that’s healthy? Is it something that’s unhealthy? You don’t know that until you actually investigate the issue.
STRINGS: We are so used to having to rely on this tool. It’s difficult sometimes for us to remove ourselves from it, but ideas that promote health, life, joy, and vitality don’t have to vary based on your size. If you are a person who does go outside and walk, when they are able to do so, it’s good to figure out ways to get your heart rate going and activate your muscles. If you are capable of accessing fruits and vegetables, have them in your diet with lean protein. If you’re capable of seeing friends and family, you might enjoy a piece of pie or cake. Live your life with health-driven behaviors where possible, and things that bring and spark joy.