Home Challenge!#ScaleFreeSummer Top 10 Reasons Why the BMI is Trash

Top 10 Reasons Why the BMI is Trash

by Erika Nicole Kendall

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.



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.


Photo credit: flickr/Susana Fernandez

You may also like


Kadijah July 16, 2013 - 2:49 PM

I remember learning my BMI about 4 years ago and it depressed me to the max. I’m 5’11, muscular and was 240 lbs at the time. My BMI said I was OBESE, I had never looked at my self as being so, so I began to think I was delusional and began to over work myself. I would workout 3 times a day, before, between and after my classes. I wouldn’t put a morsel in my mouth without measuring and weighing. I even stopped going to social gatherings because I was afraid that if I ate half a slice of cake, I’d gain the weight back. Did I lose weight? Yes, but I gained it all back because It was unhealthy and unrealistic FOR ME. Once I talked to some random women on the street (with a killer body, btw) who heard me talk about my BMI reading I was obese. She advised me to disregard, talk to my doctor and reevaluate my regimen. Best decision, my doctor agreed that I was a little overweight, but not obese by any means.

christine September 3, 2013 - 12:17 PM

smh! If I paid attention to that bmi madness I would look like a crack head! I’m 5’9′ wear a size 12. My doctor told me I needed to lose weight she’s all of 90 pounds soaking wet. I just looked at her and said ok. For me anything over 200 pounds kills my kness, but my frame is kinda small. I know women who are my height and can rock 220. If you’re healthy the scale shouldn’t matter

Clara July 16, 2013 - 3:52 PM

This came up on my bloglovin feed and I nearly skimmed past but so glad I clicked and read! Even at my fittest my BMI did not fall within the “normal” BMI range for my height, and although I try not to get bogged down by these things it always did frustrate me!
It’s another important reminder to not concentrate on scales, or what other people deem as “normal”. Thanks for posting!

Ceej July 17, 2013 - 2:24 AM

Could this be why there’s suddenly an “obesity epidemic”? If the definition of “ideal weight” is narrowed, then more people would fall outside the category, right?

Erika Nicole Kendall July 17, 2013 - 7:25 PM

I don’t know about that, and if that was the initial goal – I suppose some research into the metamorphosis of the BMI couldn’t hurt? – but I do recall reading that the CDC shifted the scale DOWNWARD, meaning that more people would be considered “overweight/obese.” Interesting, how that works.

Annette July 17, 2013 - 1:38 PM

Unfortunately, my health insurance company and many medical professionals don’t keep up and uses it as the end all and be all in terms of weight control.

BMI don’t take into account individual musculature. Serena which is practically all muscle. I wonder if she would be outside the parameters. Since I carry most of my weight in my thighs I need to firm them up. Yet I wonder how much is lose skin, muscle and just fat.

BrainyBabe July 17, 2013 - 4:55 PM

“The BMI was created before slaves were free” and therefore did not include people of African descent. Nor did the calculations include women. I think you’re on to something here. As a member of both those previously discounted groups, I have found that some of the fittest members of my family are never within the “acceptable” BMI limits. I agree with you: focus on those key health numbers (I.e. blood pressure, cholesterol, insulin levels).

Jessi July 18, 2013 - 7:51 AM

Hi just came across your blog, great article. Really great questions and discussion about something that gets thrown around as “gospel” about weight management/obesity. I never really bought into BMI as a gauge for my weight just went off my pant size or how i look in the mirror, but I will have a look at the source info you have linked and the next time I hear someone talking about it a the gym I’ll have a discussion with them and point them this way. thanks!

Kami July 19, 2013 - 8:01 AM

In the future I will focus on more on body fat. My goal is to go from thirty percent boy fat to 19 percent. Another goal is keeping up with this clean eating exercise. Another goal is to workout five days a week. Hopefully these doctors stop being so dependent on this BMI. Maybe they could get rid of it and use another system that will work for all people especially women.

Renee July 20, 2013 - 4:36 AM

Yep you’re right, the BMI is not universally accurate at all. I remember a few years ago when I lost a bunch of weight due to a medication I took for a health issue. My weight fell down to 118 (I’m 5’4”) which is technically in the “healthy” range for someone my height. I looked absolutely emaciated. My doctor was horrified lol. She said I was the first patient she had that was in the healthy range but clearly was no longer healthy upon sight. (Due to the area I live in, I’m willing to bet I’m also her first black patient, which would explain a lot about the BMI “failing” me.)

Disco Diva December 11, 2013 - 9:23 AM

I have a coworker (white male, pretty tall) who lost 130 lbs. He looks GREAT! He is 190 lbs. He did it using Weight Watchers. He was so happy to reach his goal and when he put his weight it he said it said Congratulations you met your goal weight! and then told him he is still overweight. There is so much more to health than lbs.

Comments are closed.