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Debunking BMI ...

Seanb_us
Seanb_us Posts: 322 Member
edited September 2024 in Chit-Chat
Just FYI:

http://www.npr.org/templates/story/story.php?storyId=106268439

Replies

  • DancinSMartiPants
    DancinSMartiPants Posts: 363
    From the website above:
    Americans keep putting on the pounds — at least according to a report released this week from the Trust for America's Health. The study found that nearly two-thirds of states now have adult obesity rates above 25 percent.

    But you may want to take those findings — and your next meal — with a grain of salt, because they're based on a calculation called the body mass index, or BMI.

    As the Weekend Edition math guy, I spoke to Scott Simon and told him the body mass index fails on 10 grounds:

    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.
  • DancinSMartiPants
    DancinSMartiPants Posts: 363
    I just had a personal revelation about BMI a couple weeks ago. According to BMI, my healthy weight range should be 140-155. However, according to a body fat analysis my body currently contains 160 pounds of lean tissue and 100 pounds of fat. at first glance those two seem to jive, but not after considering that NO ONE can be 0% body fat. My goal is to be about 18%-20% body fat--in shape but a little curvy which puts me more like 185 pounds.
  • barbiex3
    barbiex3 Posts: 1,036 Member
    who cares?

    most people can follow the BMI to see if they are overweight or obese. Most people do not have such an outrageous amount of muscle that it throws off the results. If you have that much muscle chances are you are a professional athlete or you are very well aware of your fitness level.

    I think BMI is fairly accurate for the average American. Many Americans are trying to put excuses on why they are overwight, so now they are accusing the BMI of being wrong. It's kind of stupid if you ask me. Sure, there are always exceptions to the rule, but generally only 10% of the population are in the outliers (several of whom are misclasses as UNDERWEIGHT)

    BMI is just a guideline. If you are my height and 180 pounds, and you wanna claim you are not overweight because BMI does not account for muscle, but you cannot even do a push up or sit up or run a mile, then my friend, you are probably overwieight!
  • DancinSMartiPants
    DancinSMartiPants Posts: 363
    who cares?

    most people can follow the BMI to see if they are overweight or obese. Most people do not have such an outrageous amount of muscle that it throws off the results. If you have that much muscle chances are you are a professional athlete or you are very well aware of your fitness level.

    I think BMI is fairly accurate for the average American. Many Americans are trying to put excuses on why they are overwight, so now they are accusing the BMI of being wrong. It's kind of stupid if you ask me. Sure, there are always exceptions to the rule, but generally only 10% of the population are in the outliers (several of whom are misclasses as UNDERWEIGHT)

    BMI is just a guideline. If you are my height and 180 pounds, and you wanna claim you are not overweight because BMI does not account for muscle, but you cannot even do a push up or sit up or run a mile, then my friend, you are probably overwieight!

    Fair enough, but I do note that the majority of your signature has you marking your success in body fat percentage. Just saying.
  • dreanance
    dreanance Posts: 246
    who cares?

    most people can follow the BMI to see if they are overweight or obese. Most people do not have such an outrageous amount of muscle that it throws off the results. If you have that much muscle chances are you are a professional athlete or you are very well aware of your fitness level.

    I think BMI is fairly accurate for the average American. Many Americans are trying to put excuses on why they are overwight, so now they are accusing the BMI of being wrong. It's kind of stupid if you ask me. Sure, there are always exceptions to the rule, but generally only 10% of the population are in the outliers (several of whom are misclasses as UNDERWEIGHT)

    BMI is just a guideline. If you are my height and 180 pounds, and you wanna claim you are not overweight because BMI does not account for muscle, but you cannot even do a push up or sit up or run a mile, then my friend, you are probably overwieight!

    Agreed. It is a TOOL. There are far better tools, sure but BMI is easy. Most people have some idea what their height and weight is and could therefore come up with their BMI easily.
  • barbiex3
    barbiex3 Posts: 1,036 Member
    who cares?

    most people can follow the BMI to see if they are overweight or obese. Most people do not have such an outrageous amount of muscle that it throws off the results. If you have that much muscle chances are you are a professional athlete or you are very well aware of your fitness level.

    I think BMI is fairly accurate for the average American. Many Americans are trying to put excuses on why they are overwight, so now they are accusing the BMI of being wrong. It's kind of stupid if you ask me. Sure, there are always exceptions to the rule, but generally only 10% of the population are in the outliers (several of whom are misclasses as UNDERWEIGHT)

    BMI is just a guideline. If you are my height and 180 pounds, and you wanna claim you are not overweight because BMI does not account for muscle, but you cannot even do a push up or sit up or run a mile, then my friend, you are probably overwieight!

    Fair enough, but I do note that the majority of your signature has you marking your success in body fat percentage. Just saying.

    lol of course. no one can argue that body fat % TRUMPS BMI ANY day. Body Fat % is always the way to go, but BMI is just a super easy way of putting you in a category. It may sound terrible to shove people in a category, but that's why is it used! haha. Body fat % is the way to go tho.
    BMI is useful for those who do not have time or the tools to do a Body Fat % testing.
  • simbatlion
    simbatlion Posts: 2
    Sure BMI has it's problems, as do most things, but the article seems like a copout to the real issue. Especially point number 10, what a joke. Take a walk outside, you don't see a bunch of crazy buff people who defy the BMI scale, you see a plethora of overweight and obese people, you can see it with your eyes, no scientific equations needed. Just another attempt at a scapegoat instead of addressing the real issue.
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