Research Suggests BMI Cannot Predict Your Danger of Dying—However This Different Metric Can

One more examine has discovered that physique mass index, or BMI—a measure of physique fats based mostly on peak and weight—is a poor indicator of general well being.

The report, revealed within the Annals of Household Medication in June, discovered that BMI is unreliable at predicting an individual’s threat of dying. However based on the researchers, there’s a more practical measurement that may be simply assessed throughout routine checkups: physique fats share, or the proportion of your physique that is made up of fats.

That metric is set by way of bioelectrical impedance evaluation, a way that sends a painless electrical present by way of the physique to estimate the proportions of physique fats, lean muscle mass, and water.

Right here’s what to know in regards to the rising issues round BMI, and why docs say physique fats share could also be a better metric.

As a result of physique composition is linked to a better threat of sort 2 diabetes, heart problems, and early dying, physicians have historically relied on BMI to judge an individual’s fats, bone, and muscle well being.

Calculated by dividing weight in kilograms by peak in meters squared, BMI can supply some sense of an individual’s well being, stated Wajahat Mehal, MD, DPhil, the director of the Yale Metabolic Well being and Weight Loss Program.

“The upper it’s, the extra possible that will probably be related to metabolic ailments,” he instructed Well being. 

However rising proof suggests BMI is a flawed indicator as a result of it doesn’t account for age, organic intercourse, or the distribution of fats and muscle.  

For instance, elite athletes typically have excessive lean muscle mass and elevated BMIs, based on Shiara Ortiz-Pujols, MD, MPH, the director of weight problems medication at Northwell Well being’s Staten Island College Hospital. “These athletes are wholesome, but when the main focus is solely on BMI, they might be mislabeled as having weight problems,” she instructed Well being. 

On the flip aspect, some folks with “regular” BMIs should have a better threat of diabetes, hypertension, and nonalcoholic fatty liver illness, Arch Mainous, PhD, lead creator of the examine and a professor within the Division of Group Well being and Household Medication on the College of Florida Faculty of Medication, instructed Well being.

“These individuals are typically referred to as ‘regular weight weight problems’ or, colloquially, ‘skinny fats,’” he stated.

With the restrictions of BMI in thoughts, researchers from the College of Florida Well being got down to examine how strongly the measure is linked to mortality. In addition they needed to know whether or not physique fats share—“a straightforward, dependable, and cheap measure of physique composition,” they wrote—may higher predict the danger of dying.

The crew analyzed well being information from 4,252 adults between the ages of 20 and 49. The info, collected between 1999 and 2004, included peak, weight, waist circumference, and physique fats share (BF%). Researchers calculated BMI and tracked mortality by way of 2019 utilizing dying certificates data.

After adjusting for a number of elements, together with age and race, the scientists concluded that:

There isn’t a vital hyperlink between a BMI categorized as overweight—outlined as 25 kg/m2 or larger—and a better threat of dying from any trigger in comparison with these with a “wholesome” BMI. 
BF% provides perception into mortality threat. These with a excessive BF%—27% or larger for males and 44% or larger for girls—had been 78% extra prone to die from any trigger.
Waist circumference is much less predictive than BF% however nonetheless related to a better threat of dying.

In keeping with Mainous, the examine “exhibits {that a} direct measure of physique fats share that’s comparatively cheap and straightforward to acquire in a physician’s workplace is superior in predicting downstream mortality threat versus the oblique measure of physique fats yielded by BMI.”

Nonetheless, the analysis doesn’t recommend that docs ought to by no means use BMI, Mainous stated. It could actually nonetheless function a easy start line to find out whether or not a affected person must shed some pounds or achieve lean muscle mass to stop continual ailments like diabetes or coronary heart illness. However it’s simply that, he stated—“a straightforward first step.”

Ideally, different metrics ought to be measured as properly. “The extra information factors we use—BMI, waist circumference, physique fats, blood strain, blood ldl cholesterol—the extra full an image we may have of affected person well being,” Mehal stated.

Fashionable machines that measure BF% utilizing bioelectrical impedance evaluation can produce leads to lower than a minute, the examine authors wrote.

Mainous hopes extra physicians will start measuring BF%. We have to deal with illness prevention, he stated, and a direct measure of physique fats share may also help us try this.

“We now have nationally consultant proof {that a} technique to do this in a reasonable and viable measure for the physician’s workplace can just do that,” he stated.