Don’t Rely on BMI (Body Mass Index)

My BMI, or “Body Mass Index,” is 26.9 – well into the “overweight” category. It’s right there on my medical chart every time I visit the doctor, and my weight tracking and food logging apps display it ominously in red to alert me that I’m in trouble. Too heavy! Lose weight! I get nagged about it from several directions.

The only problem is, the BMI can’t be correctly used to determine whether a person needs to lose weight or not. In fact, “losing weight” is the wrong issue to be thinking about entirely. Instead, if we need to be thinking about losing anything, we should be thinking about fat, not weight.

A few days ago, on Saturday, August 29, 2015, I did a DEXA (or DXA) body composition scan – the most accurate kind of body composition test available. My results showed I have a perfectly healthy body fat percentage, excellent fat distribution (less belly, more hips/legs), great Relative Skeletal Muscle Index (RSMI), and right-at-the-top-of-the-chart bone density. As the gentleman explaining the charts and graphs on my printout said, “You got all A’s!”

So the BMI can go suck an egg.

People who have lots of muscle and “good bone” (as horse people put it) will often have a high BMI, while they are actually quite healthy. And, probably a more widespread problem, others will have low body weight, and a “healthy” BMI, but they have little muscle mass (that’s called being “skinny-fat”). They are not healthy and lean, just small. Either way, don’t trust the BMI to tell you how you’re doing. Sure, it can indicate something that needs further investigation, but it cannot definitively determine whether you are “fat” or not.

That’s not even what it’s for – it’s being applied incorrectly. Here’s more about why you should not be relying on the BMI as a measure of your health or fitness:

Read or listen to “Top 10 Reasons Why The BMI Is Bogus,” from NPR’s Weekend Edition Saturday, 4 July, 2009.

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