Medical Group says BMI alone is not enough to assess health and weight
The American Medical Association voted Tuesday for a new policy that encourages doctors not to rely solely on body mass index, a long-used but potentially misleading measure, when assessing weight and health. Policy officially recognized the “historical damage” of BMI and states that the metric has been used “for racial exclusion”.
“It’s a pretty big shift,” said Dr. Cynthia Romero, director of the M. Foscue Brock Institute for Community and Global Health at Eastern Virginia Medical School, who was involved in developing the new policy. “Now we really need to be more aware and holistic when it comes to patient care.”
The policy could be a first step toward moving away from a drug model that urges people above a certain BMI to lose weight, without considering the toll these weight loss measures can take, said Dr. Scott Hagan, an assistant professor of medicine at the University of Washington who has studied obesity and was not involved in the decision. “It’s a really big deal,” he said. While the AMA is influential in the medical community, the new recommendation is just a suggestion for doctors, not a strict rule for them to follow.
The association, one of the largest medical groups in the country, will now advise doctors not to use BMI alone to assess whether a patient is at a healthy weight. The AMA suggested that doctors also consider factors such as someone’s visceral fat (the fat stored in the abdominal cavity and around the organs), body fat index (a calculation that uses hip circumference and height), the percentage of fat, bone, and muscle in a person’s body, and genetic and metabolic factors, such as abnormal blood sugars or thyroid tests.
The body mass index is one simple calculation with a complicated past. You generate it by taking your weight in kilograms and dividing it by the square of your height in meters. Critics have long argued that the metric is an inaccurate measure of health, since someone high in muscle and low in fat can have the same BMI as someone who is obese.
“BMI is just a very poor measure of overall health,” said Dr. Hagan. “Someone with an elevated BMI can be perfectly healthy.”
And where you carry weight matters, said Leslie Heinberg, director of the Cleveland Clinic’s Enterprise Weight Management Center. Belly fat is associated with higher rates of type 2 diabetes and cardiovascular disease, compared to fat around the hips, she said, a nuance the metric can’t capture.
“There are many concerns about how BMI has been used to measure body fat and diagnose obesity, but some physicians find it a useful measure in certain scenarios,” Dr. Jack Resneck Jr., who stepped down as president of the AMA, wrote in a statement this month, adding that doctors need to understand both the benefits and limitations of the metric.
At the population level, BMI is “probably the best thing we can do” when assessing large groups of people, said Iliya Gutin, a program associate at the National Academies of Sciences, Engineering and Medicine and a research affiliate at the University of Texas at Austin who is also the has studied metrics and said he welcomes the new policy. It is also cheap and efficient.
But BMI is “not this magic or powerful number that determines how healthy or sick you will be,” said A. Janet Tomiyama, a professor of psychology at the University of California, Los Angeles, who has studied BMI and said she was “in shock” about the new policy. “For the longest time I’ve been in this emperor-has-no-clothes situation where I just couldn’t understand why really smart doctors continue to rely on something so obviously flawed.”
The new policy also highlights that BMI is based primarily on data from previous generations of non-Hispanic white people, making it difficult to apply the measure to a wider population.
Despite opposition to the metric, it has remained widely entrenched.
“A lot of our standards and guidelines are built around it,” said Dr. Gutin. “Once that happens, it’s very hard to shift the inertia.”