Are you still using BMI to measure your health? Don’t, docs say

Are you using BMI to measure your health?. Getty Images

You go to the gym and watch what you eat, but when you plug in your height and weight, a body mass index calculator labels you as overweight or obese.

U.S. doctors suggest BMI is incorrectly categorizing millions of people as unhealthy in a study they say puts the “nail in the coffin” for the health measurement.

Scientists out of the University of California in Los Angeles say BMI is labelling 54 million Americans as “unhealthy” even though they aren’t.

“Many people see obesity as a death sentence,” Dr. Janet Tomiyama, a UCLA psychology professor and the study’s lead author, said in a university statement.

“But the data shows there are tens of millions of people who are overweight and obese and are perfectly healthy,” she explained.

The researchers looked at BMI – which is calculated by dividing a patient’s weight in kilograms by the square of the person’s height in metres – along with other health factors, such as blood pressure and glucose, cholesterol and triglyceride levels in the population.

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Turns out, 47 per cent of Americans who are “overweight” according to their BMI are actually pretty healthy based on the other markers of health. That’s 34.4 million people.

Another 19.8 million people who were “obese” under the BMI’s standards were actually healthy.

But 30 per cent – or 20.7 million people – who fell under the “normal” BMI had poor results when it came to blood pressure, glucose and fat levels.

BMI is used by some U.S. companies to determine workers’ health care costs and it’s even a tool in deciding health insurance premiums. The researchers warn that healthy people with a poor BMI could be paying penalties for the allegedly outdated measurement.

“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.

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In Canada, doctors don’t think BMI holds much value when looking at a single person’s health, too.

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“BMI is a measure of bigness. While useful when considering a population, it’s virtually meaningless when considering the patient sitting across from you in your office,” Dr. Yoni Freedhoff, a physician at the University of Ottawa and the Bariatric Medical Institute, told Global News.

“Assuming a person’s lifestyle is unhealthy because their BMI is high is as unwise as assuming a person’s healthy just because they’re skinny. I know plenty of skinny people with awful lifestyles, and plenty of people with obesity whose habits are healthier than mine,” Freedhoff said.

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Dr. Sean Wharton, who runs a weight management clinic and is an internal medicine specialist at Toronto East General Hospital, says where BMI holds value is gathering large-scale snapshots.

“It does have some merit when we’re doing bigger epidemiological studies. We still use BMI when talking about populations,” he explained.

In a doctor’s office, however, it doesn’t hold as much clout.

“If a doctor sees someone with a high BMI but is an active person with no medical problems, they aren’t going to spend time working on that person’s weight. I believe the majority of family doctors actively talk to patients with health problems and not just looks at their BMI to give them advice,” he said.

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