Over the past few years, body mass index (BMI) effectively has become a proxy for whether or not a person is considered healthy, and many U.S. companies use their employees’ BMIs as a factor in determining workers’ healthcare costs. But a new UCLA study has found that using BMI to gauge health incorrectly labels more than 54-million Americans as “unhealthy,” even though they are not.
“Many people see obesity as a death sentence,” says A. Janet Tomiyama, PhD, assistant professor of psychology and director of UCLA’s Dieting, Stress and Health Laboratory. “But the data show there are tens of millions of people who are overweight and/or obese and are perfectly healthy.”
The scientists analyzed the link between BMI — which is calculated by dividing a person’s weight in kilograms by the square of the person’s height in meters — and several health markers, including blood pressure and glucose, cholesterol and triglyceride levels, using data from the most recent National Health and Nutrition Examination Survey. The study found that close to half of Americans who are considered “overweight” by virtue of their BMIs (47.4 percent, or 34.4-million people) are healthy, as are 19.8 million who are considered “obese.”
Given their health readings other than BMI, the people in both of those groups would be unlikely to incur higher medical expenses, and it would be unfair to charge them more for healthcare premiums, Dr. Tomiyama says.
Dr. Tomiyama found in previous research that there was no clear connection between weight loss and health improvements related to hypertension, diabetes and cholesterol and blood-glucose levels, and she was surprised at the magnitude of the numbers in the latest study. “There are healthy people who could be penalized based on a faulty health measure, while unhealthy people of normal weight” — more than 30 percent of those with BMIs in the “normal” range, or some 20.7-million people, according to the study — “will fly under the radar and won’t get charged more for their health insurance,” she says. “Employers, policy makers and insurance companies should focus on actual health markers.”
Jeffrey Hunger, a doctoral candidate at UC Santa Barbara and co-author of the study, says the research shows that BMI is a deeply flawed measure of health. “This should be the final nail in the coffin for BMI,” he says. Hunger recommends that people focus on eating a healthy diet and exercising regularly, rather than obsessing about their weight.
A proposed Equal Employment Opportunity Commission rule would allow employers to charge higher insurance rates to people whose BMI is 25 or higher. A BMI between 18.5 and 24.99 is considered normal, but the study emphasizes that normal BMI should not be the primary goal for maintaining good health.
Misclassification of Cardiometabolic Health when Using Body Mass Index Categories in NHANES 2005 – 2012,” International Journal of Obesity, February 2016