Quizzes & Puzzles29 mins ago
Does The Bmi Need Fixing?
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I'd say it's been complete Balearics for most of the last half century, so this is well overdue.
I'd say it's been complete Balearics for most of the last half century, so this is well overdue.
Answers
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Yes. 9 reasons it is flawed // 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 mathematicia
12:17 Tue 29th Jan 2013
Well that's because people tend to forget the caveat that accompanies it
A BMI of over 30 is considered obese *provided your waist measurement is over 40" for a man or 35" for a woman*
This proviso is often ignored which leads people to make the simplistic comparison to top athletes and draw the erroneous conclusion that it must therefore be complete rubbish
A BMI of over 30 is considered obese *provided your waist measurement is over 40" for a man or 35" for a woman*
This proviso is often ignored which leads people to make the simplistic comparison to top athletes and draw the erroneous conclusion that it must therefore be complete rubbish
Yes. 9 reasons it is flawed
// 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.
//
// 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.
//
Well how can I not give that Best answer! Thanks Gromit for a very thorough explanation. I note in the artical that the new calculation isn't much different from the old so I guess most of Gromits's post applies their too. I think we need a more relevant body composition test but that is not as easy to carry out asd an arithmetic based test.
It is well known it is a rough guide and has to be considered with other known information. I think it is just fashionable to criticise its shortcomings, but that's ridiculous. Sure if one has something else one wishes to use, then go ahead, but I don't see any real issue so long as one has the intelligence to interpret the result sensibly.
Not much change for me
Old BMI=22.04, New BMI=22.30.
Is this your source Gromit - Keith Devlin?
http://
Old BMI=22.04, New BMI=22.30.
Is this your source Gromit - Keith Devlin?
http://
Most people who use BMI regard it as a rough screening test, and faced with a athletic young man with a highish BMI wouldn't dream of advising him to lose weight (as Keith Devlin's doctor seems to have done).
Not sure what all the alternative methods to measure obesity are, but am pretty sure they would be time consuming and/or costly.
Interesting article from the Wall Street Journal here..
http://
Not sure what all the alternative methods to measure obesity are, but am pretty sure they would be time consuming and/or costly.
Interesting article from the Wall Street Journal here..
http://
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