Body Mass Index is used by everyone from insurers to health professionals to determine whether someone is at a healthy weight. According to the index, which is calculated by dividing a person’s weight by the square of the person’s height, someone with a BMI of 18.5 to 24.9 is “healthy,” whereas a BMI of 25 to 29.9 is classed as “overweight” and a BMI of 30 or higher is categorized as “obese.”
But these numbers do not directly correlate with physical health, according to a study of 40,420 people published this week in the International Journal of Obesity.
“This should be the final nail in the coffin for BMI,” Jeffrey Hunger, co-author of the paper and a doctoral candidate at UC Santa Barbara, said in a statement.
UCLA researchers, led by psychologist Janet Tomiyama, used data from the National Health and Nutrition Examination Survey to analyze the connection between participants’ BMI and key signs of health—such as blood pressure and cholesterol, glucose and triglyceride levels. They found that 47.4% of overweight people are, in fact, healthy, as are 29% of those labeled “obese.” Conversely, more than 30% of those within the “healthy” weight range were found to be metabolically unhealthy.
The statistical findings indicate that across the US, an estimated 54 million Americans with high BMIs are in fact healthy. These people do not have an increased likelihood of incurring higher medical expenses and so it would be unfair to charge them higher-insurance premiums.
“There are healthy people who could be penalized based on a faulty health measure, while the unhealthy people of normal weight will fly under the radar and won’t get charged more for their health insurance,” said Tomiyama. She added that employers, policy makers, and insurance companies should focus on “actual health markers.”