Chasing The BMI

This is a tale of woe. I went in for my annual check-up awhile back. I thought I was fit, lean. I lift weights. Although it may be a struggle, I can run a half-marathon at a moment’s notice (this is a life skill). Yet, after getting my height checked and using the doctor’s scale the Body Mass Index (BMI) chart told a far different story. I was lumped into the overweight category. And I needed to work on it. This was Mr. Doctor talking.

My first thought: How in the hell could this be possible? Let me leave you with this rule of advice. If you’re not ready for criticism, don’t ask for feedback. Also, if a person is not ready for feedback don’t give it. Mr. Doctor walks a fine here. There is an art to the annual checkup. Some got it. Most don’t. With little time to make an impact, I guess you have to be blunt. It’s a job hazard.

I’d like to think I’m always open for critique now and then. According to most self-help blogs, magazines and life coaches, it is how you get better. But when it comes to weight … Sometimes, that’s a tough pill to swallow. To be brutally honest, it’s damn hard.

Of course, the denials came. I ran a half marathon. It was a solid time even, a good 15 minutes less than my goal. And you’re not exactly fit and trim, Mr. Doctor. Have you looked at your mid-section lately? It’s hard to make the bad thoughts go away. At least the words didn’t leave my mouth, they can’t come back once that happens. Yeah, I was told I ate too much but that’s not an excuse. Personal attacks aren’t cool. Sorry, Mr. Doctor.

And my key question, who created the BMI? What could they possibly know? With medical science these days (we’ve mapped the genome), something this old has no business being used in conjunction with modern medicine. And there is no reason it should be calling me overweight.

If you’re curious (otherwise, skip a ahead), Adolphe Quetelet developed the BMI from 1830 to 1850. The BMI, or Quetelet index, is a value defined by an individual’s weight and height.

I’m going to get technical here (it’s boring but important). The BMI is defined as body mass divided by the square of the body height. It is universally expressed in units of kg/m2, weight in kilograms and height in meters. If pounds and inches are used, a conversion factor of 703 (kg/m2)/(lb/in2) must be applied. Yeah, this doesn’t make sense. I haven’t taken math in years. With the internet these days, does anyone figure anything out by hand anymore? Just go here, it does the calculation for you. However, the calculation is important. I’ll get to that in a bit.

The BMI became popular back in the 1970s as prosperous western societies started to, ugh, swell. When I say western society, that’s the good ole US of A. This has to do with our diets. Our consumption habits have drastically changed. Today, fruits and vegetables are more expensive compared to processed foods. You can get a frozen pizza for the same cost as a head of lettuce. And it’s far easier to make a pizza than a salad. We get what we incentivize.

But I like my processed foods. The BMI has to be wrong. Some scientists agree and feel the BMI is appropriate for population studies and inappropriate for individual evaluation (Nevertheless, due to its ease of use and low-cost, it has come to be widely used for preliminary diagnosis).

In my research, I took all criticisms of the BMI to heart. I was determined not to be classified as overweight. Here are a few and why I thought the BMI doesn’t apply to me:

Math: I always thought the BMI didn’t make sense for short people. Based on my height and weight, I’m supposed to weigh less than 158 pounds. That’s crazy ridiculous. I weighed 158 pounds in Junior High. Maybe. However, the BMI ignores the basic scaling law, which states that mass increases to the 3rd power of linear dimensions. I read this on Wikipedia. I wasn’t smart enough to come up with it on my own. Hence, taller folks always have a larger BMI. Unfortunately, it works for short people. Damn it.

Ignores variation in physical characteristics: The BMI doesn’t account for body frame size. Since I have broad shoulders and played football, I must be ginormous. Actually, this doesn’t fit either. Damn it again.

The Arbitrary Denominator: The exponent of 2.0 in the denominator for BMI is arbitrary. This is why understanding the math is important. For my weight, height and age, I should technically be using a factor of 1.9. So, I did the calculation by hand. Yes, I really did, but this makes the problem worse. I should weigh 155 pounds. Damn it times three now.

BMI is particularly inaccurate for people who are very fit or athletic: This is me. I can’t be overweight. I ran that half marathon. Runners are a curious lot, they talk about their feats all the time. It’s a badge of honor. Most people just don’t care. Have I mentioned I ran a half marathon?

Yes, athletes look at body fat, determined by such techniques as skinfold measurements, underwater weighing (Archimedes Principle). But in reality, the daily jog and occasional weight lifting session doesn’t put me in the athletic category. I’m not trying out for the Olympics, nor do I play professional baseball. Damn it. Four strikes and you are really out.

I know the BMI metric is quick and arbitrary. It is flawed. But it is a good guide for simple goals. Simplicity always beats complexity.

Like most, it appears I swelled after high school. Apparently, there is a reason why people in the 50s and 60s look so tiny. So, I’m going to chase BMI 24. For me, that’s 155 or 160 (sigh) depending on the denominator I choose to use. Seemingly impossible goals are the ones worth chasing. Or, maybe I should make a dumb bet with someone. Or, better yet, I can work on a few more excuses on why I can’t get there.

Other Notes:

BMI calculators are fairly easy to find. This is another one.

Information on the BMI history. It’s amazing that Wikipedia has destroyed Encyclopedia Britannica. Remember using these? They were glorious.

And yes, I am going to chase BMI 24, even if it kills me.