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BMI: Braindead, Meaningless, Insidious

Debbie says:

Kate Harding at Shapely Prose has put together a slide show which demonstrates the vast stupidity of BMI. It’s quite long (45 slides), but you don’t need to watch the whole thing to get the point.

Meanwhile, The Rotund offered “guess my height and weight,” and then provided really cool graphs of the responses. What she proves without question (which most fat people already know) is that very few people know how big 200, 300, or 400 pounds are–and even when you do know in general, weight distribution makes guessing very complicated.

Even though one picture is worth a thousand words (and thus Kate’s slide show is worth 45,000 words and The Rotund added another thousand), I can’t resist adding a few words of my own.

BMI, which is almost universally accepted in the United States, and much of the rest of the world, has no medical history. It was invented by Adolphe Quetelet, a Belgian statistician, and it was adopted without question or examination by the medical profession. It is in no way a medical concept. In fact, the result of our best existing study on BMI and health caused the CDC to drop its estimates of death caused by obesity from 400,000 per year to 25,000 per year.

BMI is “body weight divided by height squared,” which makes it even less useful for short people than it is for anyone else. As you will see from the slide show, it does not take muscle mass into account. Most professional football players are “morbidly obese” by BMI standards. It is completely blind to measures like exercise levels, heart rate, etc. Some efforts have been made to incorporate age (i.e., to have different measures for children), but they are not especially widely accepted and, like the simple form of BMI, no external factors are included.

Frankly, BMI is roughly as useful a medical concept as “the vapors,” or “hysteria.” It would be funny if it wasn’t so frequently used as a weapon against all of us. Our best hope is that these projects will help drive some much-needed nails into BMI’s coffin.

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10 Responses to “BMI: Braindead, Meaningless, Insidious”

  1. Lynn Kendall Says:

    I had no idea there wasn’t any medical research backing BMI. I knew that it was weighted (Ha!) against very muscular people. I didn’t realize that is was tougher on those of us of the shorter persuasion.

    I swallowed the Kool-Aid they offered me without even checking who had mixed it, or with what purpose. I need to make sure that doesn’t happen any more.

  2. Lizzy L Says:

    Given the vacuousness of the BMI measurement, it’s stunning to me that BMI charts are all over my doctor’s office at the local Kaiser hospital. My dr, who is not a stupid woman, would probably defend the use of BMI as better than nothing — but it isn’t better than nothing! It’s bad information. It’s wrong. It’s like using the medieval theory of humours to diagnosis and treat a condition. *sputter*

  3. Rachel Says:

    The medical journals I read use BMIs. I nearly think they all do. These aren’t fringe publications, either. Weird.

  4. janet Says:

    Wow, that’s a great slide show! I am currently “overweight,” but I have also been “normal” and “obese.”

    I think the reason that medical researchers use BMI is that, stupid as it is, it’s an objective measurement. That doesn’t make it meaningful, but so little in medicine is measurable, especially when it comes to “lifestyle,” that people grasp at anything quantifiable.

  5. Slingshot Says:

    Well apparently I’m too fat for the Navy based on my weight and height… I wonder why.

  6. Laurie Says:

    BMI is truly surreal. In Japan right now the “weight magic” is waist measurement.

  7. Karl Says:

    Well, not meaning to offend anyone, but %90 of the people are in the right category. BMI might not be dead accute but it gives roughly the correct tendency.

  8. Kenneth Says:

    soooo……the 10% of us who don’t fit? irrelevant?

  9. Caitlyn Says:

    There is medical research to back it up, particularly as a research tool. A quick google will bring up all sorts of information. I don’t know where you got such rubbish.

    BMI has its limitations, certainly. It is more useful for researching population health than anything else, and it’s not great for diagnosing individuals as over or underweight. But it can be helpful for giving the average person guidelines as to what their weight should be, and for tracking progress towards a healthy weight.

    Statistically it’s a good predictor of health outcomes, so it’s worth keeping around.

  10. Debbie Says:

    Caitlin, thanks.

    I disagree, and here’s part of why:

    It’s not such a good predictor of health outcomes, at least as it is used, or people with “overweight” BMIs would not live longer than people with “normal” ones. And if it isn’t good with individuals, how can it be helpful for an average person (an individual) to know what their weight should be?

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