Doctors and U.S. companies alike have long relied on the body mass index (BMI) as a proxy for an individual’s health. However, new research published in the International Journal of Obesity suggests using BMI to gauge health miscategorizes more than 54 million Americans as "unhealthy."
Using data from the Centers for Disease Control and Prevention's (CDC) National Health and Nutrition Examination Survey, lead researcher A. Janet Tomiyama and her colleagues studied the link between BMI and several other health markers, including blood pressure, glucose, and cholesterol and triglyceride levels. They found that nearly half of individuals who are considered overweight by way of BMI were actually metabolically healthy, as were 19 million people with a BMI associated with obesity. For reference, the CDC cites a normal BMI falls between 18.5 and 24.9.
"Many people see obesity as a death sentence," Tomiyama said in a statement. "But the data show there are tens of millions of people who are overweight and obese and are perfectly healthy."
To boot, researchers found more than 30 percent of individuals in the normal or healthy BMI range were metabolically unhealthy. Overall, they believe using BMI as a proxy for health has led to nearly 75 million U.S. adults being misclassified as metabolically unhealthy or healthy.
For those who are overweight and metabolically unhealthy, simply losing weight may not improve their health. Tomiyama cited previous research that suggests weight loss has a slight impact on diastolic and systolic blood pressure, fasting blood glucose, cholesterol, and triglyceride levels, indicating no "clear connection" between weight loss and health improvements related to hypertension, diabetes, and cholesterol and blood glucose levels.
"This should be the final nail in the coffin for BMI," said study co-author Jeffrey Hunger.
The findings come on the heels of a recent proposal from the U.S. Equal Employment Opportunity Commission (EEOC) that would allow employers to charge employees who fail to meet health criteria up to 30 percent more for health insurance. This would mean individuals with higher BMIs could pay higher insurance premiums based on what more experts believe to be a flawed measure of health.
"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," Tomiyama said, referring to the proposed EEOC rules. "Employers, policy makers and insurance companies should focus on actual health markers."
A great example of people who are considered overweight, but are actually healthy are professional athletes. According to NPR, the Denver Broncos' average BMI falls in the overweight or obese range.
"Their muscle mass can boost them into the obese range, even though they're healthy and physically fit," NPR reported. "Based on players' height and weight on the NFL website, there is no Denver Broncos player with a normal BMI, calculated at 18.5 to 24.9." (This feels like a good time to remind you of these healthy recipes for your Super Bowl party).
Instead of focusing on BMI, which could lead to people obsessing over their weight, researchers recommend people focus more on eating a healthy diet and getting regular exercise.
Source: Tomiyama AJ, Hunger JM, Nguyen-Cuu J, Wells C. Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005–2012. International Journal of Obesity. 2016.