The BMI Is Inaccurate…Which Means You Are Fatter Than You Thought

You know that BMI (body mass index) calculation that said you were overweight? It was wrong. But, before you rejoice, you should know that there’s a good chance it should have said you were obese instead.

Published yesterday in the Public Library of Science’s PLoS One journal, a new study suggests that the BMI formula may be underestimating obesity nearly 40% of the time. That could move a lot of Americans into a dangerous category–one that they were already in, but just didn’t know it.

Instead of BMI, the study says we should rely on something called a dual-energy x-ray absorptiometry (DXA) scan, which provides a more accurate measurement of the amount of fat (and muscle mass and bone density) in a body.

Not that the BMI measurement was ever fully-embraced in the first place, according to study author Eric Braverman, a clinical assistant professor of neurosurgery at Weill Cornell Medical College.

Some people call it the ‘baloney mass index’. People aren’t being diagnosed [as obese], so they’re not being told about their risk of disease or being given instruction on how to improve their health.

All of this is interesting, but it leaves us in a major dilemma. How do we know what category we fall into now? The BMI was pretty easy to calculate–you just look at your height-to-weight ratio. But now we have to get a fancy x-ray to tell us whether we’re overweight, obese or just “big-boned”?

As if that’s not bad enough, the study also found that more women than men were adversely affected by this, with nearly half of the study’s female participants whose BMI numbers originally identified them as “overweight” were actually determined to be obese. According to Braverman, BMI is most misleading for older women, since they lose muscle and bone and replace them with fat faster than men.

So while the CDC says roughly one-third of Americans are obese, this study suggests the actual figure may be closer to 60%. Yikes.

Photo: Thinkstock

 

 

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    • Jennifer

      You may be fatter but not me! Woop Woop! I’m still normal!