Body mass index or BMI is not a completely correct measure of health, and may be wrongly labelling millions of people as ‘unhealthy’, a new US study has found.
Over the past few years, body mass index (BMI), a ratio of a person’s height and weight, has effectively become a proxy for whether a person is considered healthy.
However, scientists at the University of California, Los Angeles (UCLA), 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. But the data show there are tens of millions of people who are overweight and obese and are perfectly healthy,” said lead author A Janet Tomiyama, an assistant professor at UCLA.
The scientists analysed the link between BMI which is calculated by dividing a person’s weight in kilogrammes by the square of the person’s height in metres and several health markers, including blood pressure and glucose, cholesterol and triglyceride levels, using data from the most recent US 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 per cent, 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 health care premiums, Tomiyama said.
The researchers also found that more than 30 per cent of those with BMIs in the ‘normal’ range about 20.7 million people are actually unhealthy based on their other health data.
About 15 per cent of Americans who are considered “very obese” by virtue of having a BMI of 35 or higher are actually healthy, researchers said.
Previous research shows no clear connection between weight loss and health improvements related to hypertension, diabetes, and cholesterol and blood glucose levels, they said.
“There are healthy people who could be penalised 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.
Jeffrey Hunger, a co-author of the paper and a doctoral candidate at UC Santa Barbara, said the research shows that BMI is a deeply flawed measure of health.
Hunger said that people should focus on eating a healthy diet and exercising regularly, rather than obsessing about their weight, and strongly opposes stigmatising people who are overweight.
A BMI between 18.5 and 24.99 is considered normal, but the study emphasises that normal BMI should not be the primary goal for maintaining good health.
The findings were published in the International Journal of Obesity.