BMI or BS?


bad-science1

 

We’ve all seen it-what is your BMI or body mass index?  And we have all cringed when we were told the numbers.  But you might not know that BMI is basically BS.

To quote this webpage Cut the waist:

The concept of BMI – a simple ratio of weight in relation to height, was the work of a Belgian statistician, Adolphe Quetelet who published his “Quetelet Index” in 1832. It is important to emphasize that Quetelet had no interest in studying obesity when he developed this index.

That’s right.  He had no interest in studying obesity.  His studies have been bastardized to penalize people not only at the doctors office, but in insurance rates and even employment.

It was Quetelet’s interest in applying probability calculus to human physical characteristics which led him to develop an index of relative weight. He used this index to study the growth of normal man, having established that during normal growth, weight tends to increase in relation to height in meters squared1.

How BMI describes various levels of body fat

After World War II, following reports of increased mortality and morbidity of overweight and obese life insurance policy holders, the validity of the Quetelet Index was confirmed as a practical index of relative body weight. Renamed the Body Mass Index, it was adopted by the World Health Organization in 1995 as a tool to quickly and easily determine level of obesity.

According to npr.org: Ten top reasons why the BMI is bogus:

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.

5. It’s bad statistics.

Because the majority of people today (and in Quetelet’s time) lead fairly sedentary lives and are not particularly active, the formula tacitly assumes low muscle mass and high relative fat content. It applies moderately well when applied to such people because it was formulated by focusing on them. But it gives exactly the wrong answer for a large and significant section of the population, namely the lean, fit and healthy. Quetelet is also the person who came up with the idea of “the average man.” That’s a useful concept, but if you try to apply it to any one person, you come up with the absurdity of a person with 2.4 children. Averages measure entire populations and often don’t apply to individuals.

6. It is lying by scientific authority.

Because the BMI is a single number between 1 and 100 (like a percentage) that comes from a mathematical formula, it carries an air of scientific authority. But it is mathematical snake oil.

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.

9. Continued reliance on the BMI means doctors don’t feel the need to use one of the more scientifically sound methods that are available to measure obesity levels.

Those alternatives cost a little bit more, but they give far more reliable results.

10. It embarrasses the U.S.

It is embarrassing for one of the most scientifically, technologically and medicinally advanced nations in the world to base advice on how to prevent one of the leading causes of poor health and premature death (obesity) on a 200-year-old numerical hack developed by a mathematician who was not even an expert in what little was known about the human body back then.

With all of this scientific evidence, why do doctors and dietitians still insist on calculating this number? And it is still all over the internet.  It’s almost as bad as the whole cholesterol is bad for you nonsense.  It isn’t-in fact, you need it to live.  But it’s a multi-billion dollar business, like weight loss.  Shhh….they don’t want you to know that it’s BS. In fact, a nutritionist on a recent diet show said “eat all the egg whites you want.  Egg yolks have a lot of fat and cholesterol”.  What nonsense!  Eggs are good for you and short of eating a dozen a day, won’t hurt you or your heart.  Cholesterol studies were funded by the drug companies that make cholesterol drugs.  Get the picture?

There is a better measurement for overall health.  Using your waist circumference is a better indicator of internal fat-which is just where you don’t want it to be.  That means your organs are fatty too and that could lead to heart disease, diabetes and all kinds of nasty health issues.  Just cause your thighs are big doesn’t mean you are unhealthy.  A waist circumference of less than 35 inches in women, and 40 inches in men is considered healthy.  Also, your waist to hip ratio comes into play.  For more detailed information on these measurements and how to measure accurately, read this article.

So embrace those chubby thighs, ladies and gentlemen.  And as always, think for yourself!

2 thoughts on “BMI or BS?

  1. BMI never takes into account muscle weight! Grrrrrrrr!!!!! As a competitive dancer who danced 12+ hours a week, I was extremely tiny because I was constantly exercising! You couldn’t even pinch any fat on me. However, I had a ton of muscle (especially in my legs) and for my height, my BMI was close to “overweight.” My gym teacher (horrible woman) even told me that my BMI was too high as a teenager. Like I said, I was super tiny. But had so much muscle. I personally resent BMI measurements!!

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