Courtesy of instapundit.com and NPR.
Courtesy of instapundit.com and NPR.
From the link:
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.
So? That's the way you do things scientifically. If the formula doesn't fit reality, then you modify the formula.
However, using the square of the height seems to me to be wrong. The volume (and mass) of a body varies as the cube of its linear dimension, not the square, if its proportions stay the same. Obviously, that's not the case with the human body, because the proportions aren't the same for different height people, but using the square is equally obviously wrong.
Consider a 5-foot tall person weighing 110 lbs. That person's BMI calculation comes out 21.5, right in the middle of "normal", which is actually pretty close to being "normal". Now, consider people 6 feet and 7 feet tall... To be equally "normal", the 6-footer would have to be about 158 lbs, and the 7-footer would be only about 216 lbs. Healthy, athletic 7-footers are actually closer to 300 pounds.
The exponent for height needs to be somewhat greater than 2 for BMI to be a meaningful number...perhaps around 2.5?
Let's look at using 2.5 and consider the same people: If a 110 lb. 5-footer is "normal", the equivalent 6-footer would be 174 lbs, and the 7-footer would be 255 lbs.
Don't those look like much more reasonable figures?
Just for fun, let's try the mathematical constant e (the base of the natural logarithm system, 2.71828...).
Again, starting with the 5-foot, 110 lb. person being defined as "normal", an equivalent 6-footer would be 180 lbs., and the 7-footer would be 275 lbs.
I think that would be a far more realistic standard than what is now used.
This is the reason that doctors do not use BMI for anything other as an additional parameter. Since most insurance companies DO want the BMI (especially when dealing with bariatric issues), the MDs are forced to continue to use it.
Although I have to point out that the tenth reason on that list is assinine.
It's a load of bravo sierra, but it's a lot easier for providers and others in the industry to use than actually measuring health.
''On a bicycle you're not insulated. You're in contact with the landscape and all manner of people you'd never meet if you were in a car. A fat man on a bicycle is nobody's enemy.''
Statistics are full of this kind of thing, which is why when you look at a statistic as reported by a statistician the wording that describes the number is very exact.
It's the mass media that interprets the number to mean something it doesn't in order to sell a story.
I think the intent was to give individuals a "quick and dirty" answer to a complex question: Would you be materially healthier if you lost weight?
Such formulas often break down at the extremes (wookies, oompa loompas, oddly shaped people, in this case). To get an accurate answer requires more inputs. But, like knowing that teenagers are high risk drivers, on the whole, it's easier for insurers than learning about individuals.
Campione Del Mondo Immaginario
I think it just needs a tolerance factor.
12 years ago, when I was 6'-2" and 260 I was really fat.
10 years ago, when I was 6-2 and 205 (quite ripped mind you) I was still fat.
Now I'm 220 (less ripped) but still fat and borderline obese.
According to the BMI chart, the last time I had a good weight I was a sophomore in High School
Reskins fans can come out of the basement now? I didnt expect to see any of you guys until you win a game.....
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But, someone like the Beaner would be getting hosed. He might fall on the low side of overweight, but could outride all of us. He should have some kind of appeals proccess available. Let him take some insurance reps up a mountain, and see if they still think he's not fit.
I'm not sure how teen drivers could prove they are not high risk; I know I was!
Campione Del Mondo Immaginario
If you want a pretty accurate assement of your body composition and your level of fitness, I highly recommend getting a Bod Pod test done. It is pretty inexpensive and gives you tons of useful info pertaining to your body make-up and things like how many calories you actually burn while resting, doing light, moderate and heavy activity. I get it done once a year at the same time in order to get a good eval. of where I am, and where I need to be.
Regarding BMI.. _Some_ doctors use it as part most I personally have been to or my wife has been to use it as the only piece. Some have even gone so far as to run blood tests and prescribe me medicine because my cholestorol was above average, but not near their "limit", but since I was off the BMI chart I'm an extreme risk and anything above average needs to be treated with medicine.
er... well next doctor please.
Last edited by evblazer; 07-10-09 at 03:07 PM.
your picture failed.
oops. teach me to not preview it was a link not a pic.
Of course it's bogus. BMI doesn't take muscle mass into consideration. The only number that you should pay attention to is bodyfat percentage. Being 200 pounds in single digit bodyfat is WAY different than being 200 pounds with 30 percent bodyfat. But BMI treats both the same. It's stupid. It's not designed for athletic people. It's designed for couch potatoes.
"When I'm on a bike, it's like I'm 14 again, racing off to the arcade with a pocket full of quarters."
The key is to realize that anythign over 50% (a majority) is not necesarily statistically relavent. I can say nickels, dimes and pennies will come out of a random coin machine and quarters will not. And if i bet on it (aka what insurance companies do) I will ultimatly come out ahead, but that doens't mean quarters aren't there.
One MORE reason BMI is bogus -- as it pertains to the 'electrical impedance test' -- your hydration level can skew the results of the test! Seen it, done it, been there.
Is there any scientific evidence to support your contention that being 200 pounds because you have extra muscle is a lot healthier than being 200 because you have extra fat? The stress on your organs, your joints, etc. is exactly the same, isn't it? And for what? Unless you need that muscle for work, why eat all that extra food? Why have that extra carbon footprint? Can anyone legitimately justify it?
The whole BMI thing is not necessarily good for thinner people either. How many of us know people who haven't exercised in years and think they don't need to because they're already thin? They probably get told "keep up the good work on maintaining your weight!" when they go for an annual physical. Yet the Cooper institute has found that sedentary thin people aren't any healthier than sedentary overweight people.
Remember Covert Bailey, that fellow who ran around North America dunking people in underwater weighing tanks back in the '80s? He found chunky people who were very lean and slender people with surprisingly high body fat %. One woman he weighed was 110 pounds and around 40% fat. She never exercised, just "maintained" her weight by going on a drastic crash diet every time it crept up, so her muscle mass just kept shrinking.
I just wish these experts would stop focusing on numbers and focus on fitness. I shudder when I see young women smoking, knowing what it's doing to their bones, hearts and lungs. People have gotten the idea that it doesn't matter how you get thin, just as long as you get thin.
Can you prove that having a lot of muscle stresses organs and joints? Strong muscles and strong joints go together. I can't think of any possible way that having a lot of muscle is going to stress organs. How on earth would it?
I don't know. I asked the question: and you're answering that question by throwing another question back at me? Gee, that's cute. I was reading lots of justifications for being bigger than we need to be, as long as that size comes from carrying extra muscle, but no evidence that that is a lot healthier in the long run than being fat. I was asking for some justification for that idea.