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BMI -- Valid, or CW

by (4258)
Updated about 2 hours ago
Created October 03, 2011 at 4:38 PM

Paleo lifestyle challenges a lot of CW, especially on diet and fitness regimen. That understood, is BMI still a valid rubric, or are there better ways to understand ratios of bone, muscle, and fat when wanting to improve fitness?

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376 · October 04, 2011 at 11:06 AM

Very thorough explanation, and I agree with you on the BMI's limitations. I have been the same height, age and weight as another women 2 dress sizes larger. BMI equates us. Density can a good thing; muscle is much denser than fat.

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5242 · October 04, 2011 at 8:32 AM

+1 - I was going to come here and answer the question with "BMI is probably a good metric for populations but not necessarily individuals".

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2889 · October 04, 2011 at 5:05 AM

And here's a steroid-free oldie-but-goodie. Mike Tyson in 1986. Probably just under 5'10" (not 5'11.5", that was theatrical padding), 217lbs. BMI=@31: http://youtu.be/87sAdIWWT_I Hell, Tyson at this point didn't even lift weights...

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4258 · October 04, 2011 at 3:11 AM

Firestorm, I used to use a wheelchair myself. I understand where you are coming from. That said, I still want to be as fit as I can, and be as healthy as I can under the circumstances.

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5477 · October 04, 2011 at 2:38 AM

thhq: I don't disagree with you at all. BUT, in this particular response, he is only focused on the "numbers" being asked about in the OP's question that relate to BMI. So, he's saying, in my interpretation, that there are much more meaningful measures than BMI and a scale. And given the focus, I agree! In different words, he is saying what you said here: "Not the best of all predictors, but not useless, especially if you need a number to tell you you're obese. That's what most people are in denial over, too." – thhq This poster makes VERY clear he is NOT in denial!

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18635 · October 04, 2011 at 1:28 AM

But that is the point thhq...this is a factor that health care professionals are now required to keep track of for all their patients, even though we KNOW it is extremely limited and means next to nothing without taking into account other measurements. WAY to much emphasis on this faulty method of body analysis.

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15976 · October 04, 2011 at 1:25 AM

For the ratios you specifically refer to in the question yes it's valid. For a measure of actual health is another question. Still though I'd say that for the bulk of the US population I'd say it's decent. I know all about the outliers like lifters who will have more muscle and still be labeled inaccurately by bmi etc. But those that fall into that category generally know it already. I'd still say a mirror is the best for personal reasons. For statistics and doing reporting the bmi is prolly the best thing at the moment.

Medium avatar
10176 · October 03, 2011 at 10:57 PM

Not the best of all predictors, but not useless, especially if you need a number to tell you you're obese. That's what most people are in denial over, too.

Medium avatar
10176 · October 03, 2011 at 9:48 PM

mem the consequence of having 35 BMI, 200BG or 200 systolic blood pressure is a heart attack. Being able to go on a hike, or feeling great with high blood pressure, doesn't offer any clues about a person's CD risk. I don't see a need for overtesting, but I don't see a point in throwing out useful tools either.

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5477 · October 03, 2011 at 7:25 PM

Eek! *experiential* *flexibility* I type to fast and am having keyboard problems as well...^^^

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5477 · October 03, 2011 at 7:24 PM

@thhq: Talking about functional fitness is quite different that talking about measurements of body health that often are not eperiential, such as degrees of strength, fleibility and mobility are. Having a very high blood pressure feels great for alot of people. Most ppl would not eperience symptoms with a 200BG, but what Firestorm is describing is quite measureable, eperiential and observable as well.

Medium avatar
10176 · October 03, 2011 at 7:11 PM

I'm not good at intuitive judgement, especially with investments and health. My body didn't tell me that my blood glucose was 200 fasting. I'm glad I got a blood test and avoided a stroke.

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10176 · October 03, 2011 at 7:06 PM

If the problem is obesity there's no need to pay to have body fat tested. Simple things like a scale and a tape measure tell you what you need to know. Some people need numbers because they don't believe their mirrors.

Medium avatar
10176 · October 03, 2011 at 6:59 PM

Paleo challenges a lot of conventional wisdom , but BMI wasn't even on my obese radar. It's a standard metric by which I was defined as obese. Maybe scale and waistline are just as good. But BMI defined both problem and goal. Incidentally all the other healthy metrics - from waistline to blood pressure to A1C - came into line as BMI came down.

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5477 · October 03, 2011 at 5:44 PM

+1- On an individual level, as the truly *most* meaningful individual progess "yardstick," I *love* your way of thinking about this. It's REAL - it's what truly matters! Thanks for taking the time to share it here. Important perspective!!!

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0bc6cbb653cdc5e82400f6da920f11eb
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19220 · October 03, 2011 at 10:05 PM

Wikipedia has a good discussion of the drawbacks and limitations of use of the BMI.

Body Mass Index correlates with body fat percentage quite well across the population however there is a great deal of variability between individuals particularly at the intermediate ranges of the BMI.

This study is discussed in the Wikipedia article: Accuracy of Body Mass Index to Diagnose Obesity In the US Adult Population. The discussion is worth reading.

bmi----valid,-or-cw

Their main findings were that for a BMI of above 30 almost everyone had too much body fat. At BMIs below 30 the variability is much greater. As you can see from the graph above many men with a BMI of 25-30 have low body fat while many men with a healthy BMI of 20-25 have unhealthily high levels of body fat.

They state that in men the BMI correlates better with lean body mass than with fat. This could explain the findings that people with a BMI of 25-30 seem to live longer than those with a BMI of 20-25. Having more lean body mass like muscle is a good predictor of health. The BMI also became less accurate as people got older.

This figure below is Figure 3. from the paper shows the variation in body fat percentage among men and women with a BMI of 25. As you can see there is a wide range of measured body fat levels at the same BMI.

bmi----valid,-or-cw

You could have a BMI of 28 and have a healthier level of body fat than someone else with a BMI of 22.

Personally I think it is useful as a population measurement. It is the only really simple measure of body fat that can look at trends over time, height and weight measurements have been taken for a long time.

It is understandable that people want a simple measure to put people into categories with but I think using it to measure individuals is arbitrary and can be unhelpful especially when people are miss-classified. Simply lowering your BMI a few points is unlikely in itself to show that you have improved your health unless you know that your body fat % has also lowered and not your lean body mass. I think too much emphasis is placed upon it now with out enough discussion of its limitations.

7b11ed525ffa23bc7257684e27488a6a
376 · October 04, 2011 at 11:06 AM

Very thorough explanation, and I agree with you on the BMI's limitations. I have been the same height, age and weight as another women 2 dress sizes larger. BMI equates us. Density can a good thing; muscle is much denser than fat.

B3e7d1ab5aeb329fe24cca1de1a0b09c
5242 · October 04, 2011 at 8:32 AM

+1 - I was going to come here and answer the question with "BMI is probably a good metric for populations but not necessarily individuals".

3846a3b61bc9051e4baebdef62e58c52
18635 · October 04, 2011 at 1:28 AM

But that is the point thhq...this is a factor that health care professionals are now required to keep track of for all their patients, even though we KNOW it is extremely limited and means next to nothing without taking into account other measurements. WAY to much emphasis on this faulty method of body analysis.

Medium avatar
10176 · October 03, 2011 at 10:57 PM

Not the best of all predictors, but not useless, especially if you need a number to tell you you're obese. That's what most people are in denial over, too.

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12540 · October 03, 2011 at 5:27 PM

I'm not sure that this is going to provide any kind of an answer at all -- but from my perspective, whether it's pounds on a scale, or BMI, etc., I think that what is -truly- relevant when considering 'fitness' is whether or not we are able to do the things we want to do in the way that we want to do them.

If your body does what you want it to do both when you're relaxing AND when you're pushing it to the limit, then you've got a good handle on functional fitness.

As much as I hated to admit it, I had to break down a couple of years ago and face the fact that, at the size that I was at, there was NO way that I was going to be able to get out of the mobility chair I was parked in... the ONLY way I was going to be able to do it was to get my body down to a size where I could do things again. I'm not all the way there -- but I can tell you that the scale and the doctor's BMI calculator have been a LOT less informational for me than whether or not I could walk to the end of the hall -- then up a flight of stairs -- then around the block -- then on a real trail-hike.

If your fitness level is such that you're having to measure your improvement by number rather than by increasing capability -- I guess I don't really see where there is any benefit to the measurement. So I guess, for me, BMI is not really a valid measure of fitness, from a primal perspective.

Bdf98e5a57befa6f0877f978ba09871c
4258 · October 04, 2011 at 3:11 AM

Firestorm, I used to use a wheelchair myself. I understand where you are coming from. That said, I still want to be as fit as I can, and be as healthy as I can under the circumstances.

Cbb1134f8e93067d1271c97bb2e15ef6
5477 · October 04, 2011 at 2:38 AM

thhq: I don't disagree with you at all. BUT, in this particular response, he is only focused on the "numbers" being asked about in the OP's question that relate to BMI. So, he's saying, in my interpretation, that there are much more meaningful measures than BMI and a scale. And given the focus, I agree! In different words, he is saying what you said here: "Not the best of all predictors, but not useless, especially if you need a number to tell you you're obese. That's what most people are in denial over, too." – thhq This poster makes VERY clear he is NOT in denial!

Medium avatar
10176 · October 03, 2011 at 9:48 PM

mem the consequence of having 35 BMI, 200BG or 200 systolic blood pressure is a heart attack. Being able to go on a hike, or feeling great with high blood pressure, doesn't offer any clues about a person's CD risk. I don't see a need for overtesting, but I don't see a point in throwing out useful tools either.

Cbb1134f8e93067d1271c97bb2e15ef6
5477 · October 03, 2011 at 7:25 PM

Eek! *experiential* *flexibility* I type to fast and am having keyboard problems as well...^^^

Cbb1134f8e93067d1271c97bb2e15ef6
5477 · October 03, 2011 at 7:24 PM

@thhq: Talking about functional fitness is quite different that talking about measurements of body health that often are not eperiential, such as degrees of strength, fleibility and mobility are. Having a very high blood pressure feels great for alot of people. Most ppl would not eperience symptoms with a 200BG, but what Firestorm is describing is quite measureable, eperiential and observable as well.

Medium avatar
10176 · October 03, 2011 at 7:11 PM

I'm not good at intuitive judgement, especially with investments and health. My body didn't tell me that my blood glucose was 200 fasting. I'm glad I got a blood test and avoided a stroke.

Cbb1134f8e93067d1271c97bb2e15ef6
5477 · October 03, 2011 at 5:44 PM

+1- On an individual level, as the truly *most* meaningful individual progess "yardstick," I *love* your way of thinking about this. It's REAL - it's what truly matters! Thanks for taking the time to share it here. Important perspective!!!

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24538 · October 03, 2011 at 10:20 PM

I liked this article, and think it sums up the limitations of BMI pretty well. Do You Believe in Fairies, Unicorns, or the BMI?: http://www.maa.org/devlin/devlin_05_09.html

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8879 · October 03, 2011 at 5:29 PM

BMI -- if it has any usefulness -- has applications to groups as a whole. Even comparing between societies and various ethnicities makes BMI, which is nothing more than a glorified height-weight ratio, of dubious meaningfulness. On an individual basis, it's no more useful than your basic bathroom scale and the height-weight charts. Getting an accurate measurement of body fat percentage seems more important.

Medium avatar
10176 · October 03, 2011 at 7:06 PM

If the problem is obesity there's no need to pay to have body fat tested. Simple things like a scale and a tape measure tell you what you need to know. Some people need numbers because they don't believe their mirrors.

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2889 · October 04, 2011 at 4:52 AM

Dorian Yates in 1993. 5'10", 257lbs. BMI = @37:

http://youtu.be/JuzU1HeFvsk

25b139cc1954456d9ea469e40f984cd3
2889 · October 04, 2011 at 5:05 AM

And here's a steroid-free oldie-but-goodie. Mike Tyson in 1986. Probably just under 5'10" (not 5'11.5", that was theatrical padding), 217lbs. BMI=@31: http://youtu.be/87sAdIWWT_I Hell, Tyson at this point didn't even lift weights...

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18635 · October 04, 2011 at 1:24 AM

But without taking into factor other measurements BMI is actually quite useless. Just a fact. Hip to waste ratio would give you more info.

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