There’s a Better Way to use BMI
Body Mass Index – better known by its handy acronym BMI – has been around for a long time. It estimates body fat by using an individual’s weight, dividing that by the person’s height, and then squaring that number. In other words, it’s a relatively simple math computation.
“It’s an easy tool that helps us tell the cardiovascular health [of a patient],” says Kristopher J. Paultre, M.D., a family and primary care sports medicine specialist with the University of Miami Sports Medicine Institute. “It’s a good indicator of your heart health.”
However, it should not be the only metric used, he adds. Rather, BMI should be one tool in a toolbox of other health metrics.
Any doctor worth his salt is looking beyond BMI. It’s just one piece of a bigger picture.
Dr. Kristopher Paultre
This belief underscores the recent decision by the American Medical Association to adopt a new policy on the BMI index.
In early summer, the AMA told its members they should pay less attention to BMI as a measure of healthy weight.
They should incorporate other metrics, such as body composition, waist circumference, and measure of visceral fat.
The AMA acknowledged that the BMI metric didn’t consider the differences in body composition and demographic groups. It was, the organization noted, “based primarily on data collected from previous generations of non-Hispanic white populations.”
Designed by Belgian mathematician Adolphe Quetelet in 1830, BMI helps explain the amount of fat mass in the general population, but it “loses predictability when applied on the individual level.”
An athlete is the perfect example of just such an exception, Dr. Paultre says. A football player, for example, will have a lot of muscle, which, in turn, will make him weigh more. This “extra” weight automatically throws off the BMI equation, though, as an athlete, he is likely to have good cardio-health.
BMI doesn’t differentiate between lean and fat body mass and doesn’t account for another factor: where fat is stored.
Where people carry their fat, like that spare tire in the midsection, is important, especially for men.
Dr. Paultre
The fat that surrounds internal organs raises the risk of heart disease, diabetes, sleep apnea, high blood pressure, fatty liver, and even certain cancers.
The debate over BMI is not an inside-baseball discussion by any means. Imperfect as it is, BMI is used in studies on obesity and insurance companies have traditionally employed it to determine eligibility for treatment of several conditions, including joint-replacement surgery and weight loss medication. What’s more, as obesity rates continue to climb, having accurate measurements of body fat and cardiovascular health is increasingly important.
In 2020, almost 42% of Americans were obese, a jump from 30.5% in just three years, according to the CDC.
Severe obesity nearly doubled in the same period. Because obesity-related diseases lead to preventable, premature death — and cost society hundreds of billions of dollars in medical costs — it is vital for both clinicians and the general population to have a firm understanding of the condition.
Dr. Paultre favors “first and foremost” the lipid panel blood test, which is a reliable screen for an individual’s risk of cardiovascular disease. The panel measures your cholesterol levels and triglycerides. He also uses an exercise stress test, which shows how your heart responds when it’s forced to pump at its hardest, and a body fat analysis, which can show a person’s total body water, protein, minerals, and fat mass content. Also important: tracking blood pressure and understanding what a person eats and how much he or she exercises.
He points out that Some of those tests are “more labor intensive” and require more time on the part of both physician and patient. That may be why he believes that BMI, for all its shortcomings, is here to stay.
“It’s not going anywhere,” he says. “People are very familiar with it, and it’s still a great tool when used with the others we have.”
Ana Veciana-Suarez is a regular contributor to the University of Miami Health System. She is a renowned journalist and author who has worked at The Miami Herald, The Miami News, and The Palm Beach Post. Visit her website at anavecianasuarez.com or follow @AnaVeciana on Twitter.
