Friday, August 19, 2011

This I Disbelieve: BMI

This I Disbelieve is a recurring piece I do on pieces of common knowledge I just can’t accept.  It’s my reaction to the old NPR piece: This I Believe.

I’ve always had toothpick arms.  If you were a geek like me who had a tendency to sweat a lot when you exercised, you would understand why.  I used to stand, shirtless, in front of the mirror and swing my arms back and forth and marvel at the fact that they didn’t just fall off.  My arms looked like they barely connected to my torso.
Worse than this.  Honest.
My wife, concerned about my lack of exercise, eventually convinced me to start working out by signing me up at a 24 Hour Fitness and getting me a personal trainer (Hi Daniel!).  At the beginning of the sessions, he took my weight and height, and used a pair of calipers to decide how much fat I had.  Those three pieces of information gave him my Body Mass Index, or BMI.  BMI is a better metric of your fitness than weight alone, giving you a number to shoot for.
"I'll be waiting for you in your nightmares, Matthew."
Then came the exercise.  At first, he just had me exercise with an inflated balloon, which was incredibly embarrassing.  It became more embarrassing when I nearly collapsed with exhaustion after one balloon session.  However, eventually I became fit.  My shoulder and arm muscles became larger and more defined and I went back to the mirror: this time marveling at the fact I had muscles.
Only, you know, with lots of body hair.
At the end of the first set of sessions, Daniel took my measurements again.  My weight had gone down.  I was evidently more muscular.  My BMI had gone up.

That’s right; according to BMI, I had gained fat when I lost weight.  I must have lost it in my bones, nerve tissues, and… I don’t know, organs?

Chalking it up as some kind of mistake, I signed up for more sessions.  I got more fit.  At the end, we took measurements and again, my BMI went up as my weight went down.

So I decided I didn’t believe in BMI any more.  Neither should you.

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