The other side of the math coin

“Lambert Adolphe Jacques Quetelet (22 February 1796 – 17 February 1874) was a Belgian astronomer, mathematician, statistician and sociologist.” — Wikipedia

Quetelet is elsewhere referred to as a polymath – a common catchall for ancient geniuses who worked across disciplines that often hadn’t yet been formally-categorized. Any polymath dining hall would probably have some Da Vinci in the decor.

Why am I talking about some clever-but-dead Belgian? Because Quetelet created the Body Mass Index – BMI for short – the number derived from a comparison of weight-to-height and popularly-used as a shorthand to categorize people as underweight, normal, overweight, or obese. If you hear someone talking BMI, you will probably, eventually, hear them say that you need to hit a certain number for optimum health – 22 is usually the number given.

You will note, at this point, that none of Quetelet’s wide-ranging interests involved medicine or biology.

According to Wikipedia, the BMI made it to prime-time in our health parlance due to a paper published in the early 70’s that suggested it was the most accurate proxy number for measuring the average body fat in a population. The paper explicitly stated that the number was not useful for individual diagnosis, and a number of studies since have confirmed this point, because the number unnaturally skews people towards seemingly-unhealthy numbers the taller they are, and doesn’t account for muscle content in more-athletic bodies. Since modern Americans are, on average, significantly taller than Belgians were 150 years ago, that ought to raise red flags right there.

And yet it is used constantly – by doctors, by insurers, on the Nintendo WiiFit, as THE signifying number of your health as determined by your weight. Why is that? Why is a formula created by a 19th century Belgian statistician with no knowledge of medical science, never intended for individual use, and with a demonstrated tendency towards inaccurate results in people who are tall or muscular, so ubiquitous?

I would suggest two reasons, related to profit-motive:

1) It is easy to compute, even for people who hate math.
2) It makes the majority of people feel fat.

If you are trying to close a sale to someone of something that will putatively improve their life/well-being, the first thing a good salesperson will do is give you reason to worry about leaving things as they are. That’s why a car mechanic will speak some dire technobabble at you while waving a part from your car which, if you understood the workings of it, you wouldn’t be going to a car mechanic. It’s why chiropractors will never, EVER say that you are fixed and never need to see them again. It’s why the free Scientology personality test has an uncanny way of telling you that you are deeply-disturbed, and in need of Scientology. So the fitness industry in America, obviously, LOVES the BMI.

I am slightly-taller than average (about 6′ even), and after losing 15+ pounds so far this year, my BMI is currently around 27.8. In America, that was considered to be right on the upper threshold of “normal” weight – until 1998, when the National Institutes of Health elected to conform to the World Health Organization’s guidelines, which set the upper limit at 25. Overnight, 25 million more Americans were suddenly, officially, fat. Or were they? Both numbers, it has been admitted – are ARBITRARY. There is no documentation to suggest that, when you pass a BMI of 25, such-and-such diseases become such-and-such percentage more likely. It is actually better for determining such disorders as anorexia and bulimia in underweight people than things like cardiovascular health in overweight people – in fact, one study demonstrated that people in the “normal” range had a HIGHER risk of dying from cardiovascular disease than their “overweight” brethren. “Obese” people, it must be admitted, were demonstrably unhealthy, but you don’t need a BMI to know that.

As I’ve said before, I have involved a lot of numbers in my quest to shave some fat off my physique and feel more energetic and healthy. But not all numbers are created equal. And a number that is designed to make you feel bad, and soften you up for people to sell you things, is not a number I want around.

So, with apologies to Mr. Quetelet, I will be disregarding his number.

(*It seems fair to admit that I have no medical education/experience whatsoever, and the information I am presenting here comes from Wikipedia. If there are legitimate medical studies out there contradicting what I have said (and not just “some guy on the Internet says so”) – I’d happily amend this post. But honestly, if you’re coming to a hack screenwriter’s blog for authoritative information about health and fitness, then you are really going about this wrong.)