The BMI Is Kinda Dumb


So there’s sort of an obesity epidemic in the United States. I don’t deny this at all, it is undoubtedly true and quite a large problem (pun intended). Unfortunately, the manner in which we’ve chosen to measure this problem, namely the Body Mass Index, or BMI, is a mindlessly incoherent, overly simplistic, stupid mess of utter nonsense.

The BMI was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet. It breaks people down into the following categories:

– Underweight (18.4 or less)
– Normal Weight (18.5 to 24.9)
– Overweight (25 to 29.9)
– Obesity Class 1 (30 to 34.9)
– Obesity Class 2 (35 to 39.9)
– Morbidly Obese (40 and above)

OK, a little simplistic, but overall, it’s not bad so far. Mathematically, it’s all based on the following easy-to-remember equation:

BMI = Mass (KG) / (Height(m))^2

OK, now we have a problem. As you can see, there is absolutely nothing about muscle composition, body fat percentage, waist size, body type or gender. I would hope I don’t need to point out that some 120 pound nerd who’s never picked up a dumbbell in his life is not healthier than a 220 pound body builder, which this equation would lead you to believe.

Let’s take a look at some examples using to do our calculations. We’ll start with professional athletes, using ESPN’s player profiles.

– Four Time NBA MVP Lebron James: 6’8″ 250 pounds, BMI: 27.5.

Prognosis: Overweight

– Two-Time NFL MVP quarterback Aaron Rodgers: 6’2″ 225 pounds, BMI: 28.9.

Prognosis: Overweight

– The large, but dominant pitcher C.C. Sabathia: 6’7″ 290 pounds, BMI: 32.67.

Prognosis: Obese, Class 1

– Lean NBA star Russell Westbrook: 6’3” 200 pounds, BMI: 25.0

Prognosis: Overweight

– Elite NFL lineman, and a very big man for sure, Carl Nicks: 6’5″ 343 pounds, BMI: 40.7.Prognosis: Morbidly Obese

Seriously, Carl Nicks is a very big man, but morbidly obese implies he can barely move. A better way to put it is that there’s hardly anyone he can’t move. One would have to guess that proponents of the BMI didn’t know that muscle weighs more than fat.

Indeed, if this Wiki answer is correct, Denzel Washington weighs 216 pounds. He’s 6 foot even, so his BMI is 29.29. In other words, he’s overweight and just a shade under being obese. According to, Arnold Schwarzenegger has a BMI of 30.8, making him obese and Tom Cruise comes in overweight as well. At least Calista Flockhart came in underweight, that’s a token victory for BMI.

And it’s not just a bunch of exceptions that prove the rule, the science is rubbish. As NPR points out that the BMI is a pile of bogus nonsense. They give ten reasons, a small sample:

“1. The person who dreamed up the BMI said explicitly that it could not and should not be used to indicate the level of fatness in an individual.

The BMI was introduced in the early 19th century by a Belgian named Lambert Adolphe Jacques Quetelet. He was a mathematician, not a physician. He produced the formula to give a quick and easy way to measure the degree of obesity of the general population to assist the government in allocating resources. In other words, it is a 200-year-old hack.

“2. It is scientifically nonsensical.

There is no physiological reason to square a person’s height (Quetelet had to square the height to get a formula that matched the overall data. If you can’t fix the data, rig the formula!). Moreover, it ignores waist size, which is a clear indicator of obesity level.

“3. It is physiologically wrong.

It makes no allowance for the relative proportions of bone, muscle and fat in the body. But bone is denser than muscle and twice as dense as fat, so a person with strong bones, good muscle tone and low fat will have a high BMI. Thus, athletes and fit, health-conscious movie stars who work out a lot tend to find themselves classified as overweight or even obese…”

You get the idea. Yes, there is such a thing as obesity, and it is a big problem, but no, the BMI is not a good way to measure it. How this useless measurement of nothing has stuck with us for so long is nothing but a giant mystery. TC mark


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