AMA doesn’t like body mass index; now what?
The American Medical Association announced in mid-June that the body mass index is an imperfect measurement and should not be used alone to determine a patient’s overall health.
The association, at a Chicago conference and as part of the AMA’s Council on Science and Public Health report, stressed the importance of acknowledging the racist and outdated origins of the BMI metric, which measures a patient’s height and weight and provides a number to determine whether a patient is overweight or obese.
Local experts said this statement is a step in the right direction for reducing weight stigma and pushing research toward a more comprehensive direction.
For many, the AMA declaration was not a surprise.
“This issue has been talked about forever,” said George Eid, an AHN physician and chair of the AHN Bariatric and Metabolic Institute. “What came as a surprise was it being recognized officially.”
Evolution of the BMI
The BMI metric was created in the 1800s not by a physician but by a mathematician, Belgian Adolphe Quetelet, for the purpose of defining the “ideal man” as a representation of a social ideal.
His subjects were non-Hispanic white men. The metric was not intended to be used in health but was taken up later by insurance companies to more easily determine coverage.
“[BMI] is a very accessible, affordable and objective piece of information,” said Katrina Han, a UPMC endocrinologist specializing in weight management and obesity medicine, and a clinical assistant professor of medicine at Pitt. “It can maybe give you a sense for what a patient might be at risk for, but it’s important to recognize its limitations.”
Namely, the BMI does not analyze fat distribution, which both Eid and Han say can impact health outcomes.
“It’s really hard to measure where the fat is,” said Eid. “That’s where the confusion comes in, and that’s why insurance companies have stuck with it.”
In the news release, the AMA notes that the BMI also fails to account for differences in age, race and gender when it comes to weight and health.
“There are numerous concerns with the way BMI has been used to measure body fat and diagnose obesity, yet some physicians find it to be a helpful measure in certain scenarios,” Jack Resneck, AMA’s president through June, said in the release. “It is important for physicians to understand the benefits and limitations of using BMI in clinical settings to determine the best care for their patients.”
Variable BMI?
Katrina Han is a UPMC endocrinologist specializing in weight management and obesity medicine.Katrina Han is a UPMC endocrinologist specializing in weight management and obesity medicine.
Both Eid and Han mentioned that the Asian population seems to experience adverse health outcomes at lower BMIs compared to other races.
The doctors chalked this up to possible genetic and lifestyle differences that can lead to metabolic changes and differences in fat distribution on the body — more abdominal fat compared to other body regions seems to be associated with worse health outcomes.
BMI also does not differentiate between lean muscle and fat.
A 2014 article in New Scientist found many Olympic athletes to be classified as overweight or obese. And one 2016 study by UCLA researchers found that BMI misidentified 47% of study participants as overweight and 29% of people as obese when they were seen as healthy by other metrics.
The participants were part of the longitudinal U.S. National Health and Nutrition Examination Survey; the study examined more than 40,000 people between 2005 and 2012.
Anti-fat bias advocates and physicians have long known of BMI’s problematic history, but Han said this is not always taught to medical students.
“I wouldn’t say this is wellknown by all physicians,” she said. “This could come as a surprise to some.”
She’s seen physicians’ lack of knowledge about BMI’s baggage impact patients.
“I have had patients come to me and express gratitude that I actually listen,” said Han. “They don’t really feel like they’ve gotten the help they need.” She’s had multiple patients tell her that previous physicians have requested they lose weight or eat less even when patients visit the doctor for symptoms unrelated to their weight.
Social standards
A 2008 study by a public health researcher at Columbia University found that those with higher BMIs were more likely to suffer stress related to stigma.
The biggest predictor of early mortality in this study was a larger gap in someone’s actual weight versus their target weight — signaling that social standards were negatively impacting a person’s body image, and thus their health.
The AMA has called for better education on BMI and its history for physicians, as well as the use of alternative metrics when determining a patients’ health. Han thought waist measurement could be one tool, because of the findings that fat around the abdomen seems to carry more health problems.
“While screening [BMI] might be a tool, it’s not the beall-end-all, and doesn’t give a clear picture of a patient’s overall health,” she said.
Hsin-Chieh “Jessica” Yeh, an associate professor of medicine, epidemiology and oncology at Johns Hopkins University with specialities in obesity and diabetes research, said that while the AMA successfully drew the public’s attention to the BMI metric, “it is important that we strike a balance between medicalizing too many people and failing to provide screening or treatment in those who are deemed to have a ‘healthy’ BMI.”
Eid agreed: Someone who has diabetes with a “normal” BMI should still receive treatment, he said.
But the fat-activist community saw the association’s statement as an empty promise.
Vinny Welsby, a consultant, author and activist for fat liberation, said “it’s mildly satisfying that the AMA is finally, very tardily, recognizing what fat liberationists and scientists have known for decades.”
Welsby worries that the policy change doesn’t meaningfully address the harm caused by BMI and pushes alternatives that continue to pick apart people with bigger bodies.
“Fat liberationists don’t want bodies to be measured in a medical setting at all,” Welsby said in an email statement. “We want health to be looked at with actual health markers. We want the correlations between fatness and health conditions to be clearly seen as a mark of weight stigma and not that adipose tissue is the cause. … We want fat people to be treated as humans and not pathologized just for existing.”
Eid said it was good to see the imperfections of BMI being acknowledged by one of the main governing bodies and hopes this is a step toward reducing stigma.
“We really need to focus on treatment beyond somebody’s size,” he said. “This shows we are catching up to realities that science already knew existed.”