A new study is calling body mass index (BMI) into question. BMI has long been considered a measure of a person's health. It's derived from dividing a person's weight in kilograms by their height in meters, and is used to classify someone as underweight, overweight, normal, or obese. More and more research has appeared in the past few years, suggesting that BMI is not all that useful in judging a person's individual health. And this latest study, published in the International Journal of Obesity, found that in many cases, BMI misses the mark.
Researchers used data from the most recent National Health and Nutrition Examination Survey to compare people's BMI measurements to other indications of cardiovascular health like blood pressure, cholesterol, and glucose levels. In the end, they found that almost half of overweight people, 29% of those classified as obese, and even 16% of people with BMIs that signal more severe obesity, were actually "metabolically healthy," meaning they didn't show the signs of poor health that we normally associate with being heavy. Moreover, more than 30% of the normal weight individuals did exhibit these risk factors for health problems.
This means that by "using BMI categories as the main indicator of health, an estimated 74,936,678 U.S. adults are misclassified as cardiometabolically unhealthy or cardiometabolically healthy," the researchers conclude in the study's abstract.
The bottom line: BMI shouldn't be the go-to measurement for general health. Alternatives to this flawed measurement are already being explored by scientists. But for now, it's much better to look at all measures of your health — including the traditional ones like blood pressure and physical fitness, but also your happiness and mental clarity.