Well, they didn’t say “trash,” but I did. Who gon’ check me?
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.
4. It gets the logic wrong.
The CDC says on its Web site that “the BMI is a reliable indicator of body fatness for people.” This is a fundamental error of logic. For example, if I tell you my birthday present is a bicycle, you can conclude that my present has wheels. That’s correct logic. But it does not work the other way round. If I tell you my birthday present has wheels, you cannot conclude I got a bicycle. I could have received a car. Because of how Quetelet came up with it, if a person is fat or obese, he or she will have a high BMI. But as with my birthday present, it doesn’t work the other way round. A high BMI does not mean an individual is even overweight, let alone obese. It could mean the person is fit and healthy, with very little fat.[…]7. It suggests there are distinct categories of underweight, ideal, overweight and obese, with sharp boundaries that hinge on a decimal place.
That’s total nonsense.
8. It makes the more cynical members of society suspect that the medical insurance industry lobbies for the continued use of the BMI to keep their profits high.
Insurance companies sometimes charge higher premiums for people with a high BMI. Among such people are all those fit individuals with good bone and muscle and little fat, who will live long, healthy lives during which they will have to pay those greater premiums.[…] [source]
I [obviously] didn’t quote the entire article, but I’d like to add a few reasons, myself:
11. The BMI was created before the slaves were freed.
The man who is responsible for our heavy reliance on the BMI, Ancel Keys, created a resource in the 1970s that used the BMI as its standard, and the practice spread rapidly because it was a quick and inexpensive means of classifying bodies.
The BMI, itself, was created by someone between 1830 and 1850, before slaves were even considered human beings. There is no reason to believe that the originators of the BMI would check their metric against multiple varieties of bodies, to ensure that certain body types or body sizes would cause the metric to give unanticipated figures.
12. The BMI was created before the slaves were freed.
No, seriously. And, if talking about slavery makes you somehow uncomfortable – probably not as uncomfortable as being a slave, but I digress – we don’t even have to talk about slaves. The BMI was created before World War I… before the sinking of the Titanic.
The BMI is older than the Klan.
It is older than the FBI, the USDA, and the Washington Monument. The BMI has been in existence longer than at least 20 of these United States have been members of the Union.
How many medical relics like this do we keep around and base public policy on, while remaining so unamended and unchecked?
13. In Keys’ study where he legitimized the BMI, he studied close to 7,500 men. Not women.
Any variances in the statistics that allowed (?!) for women to be included came well after Keys’ study, well after the BMI had been embraced as a standard. Women, and the varieties of ways in which our bodies differ from our male counterparts, were not given the opportunity to counter the metric to prove that maybe, just maybe, all bodies – regardless of gender – aren’t just “variations on a man’s body” and can’t be statistically valued as such.
14. The BMI penalizes those who are muscular.
When I was consistently training for fat loss, I had a flurry of emotions when my weight dropped into the “normal” range for BMI.
And, when I started training exclusively for muscle, I remember having a serious wtf?! moment when, even as my body fat percentage was dropping and my fitness was improving, my BMI crept back into the overweight range. Why? Because it merely accounts for height… and weight. There is no delineation between qualities of said weight – since the difference between “normal weight” and “underweight” are determined by a mere decimal point, everything from a bad liver to osteoporosis can be responsible for someone being classified as underweight; and everything from an enlarged heart to “I haven’t pooped in days” can be responsible for an “overweight” classification.
At that point, I knew it was a wrap. I just couldn’t be bothered any more.
I’d sooner learn my body fat percentage and pay more attention to my physical fitness and appearance than I would hang my hat on the damn BMI.