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The New BMI Calculation & Why I Don't Care

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Tuesday, January 22, 2013

Back in the stone age of medicine - which is, in my opinion, anytime prior to the work of Snow and Pasteur - a formula was created to capture in a number one's healthy weight - the body mass index or BMI.

Most of you are familiar with the BMI.

Some of you can probably quote your BMI without doing the calculation.

And what BMI value you are working toward.

The BMI formula is a simple one as formulas go:

BMI = weight in kilograms divided by the square of your height in meters.

So for me, that ends up being...

116.8 / (177.8 x 177.8)



And if I had my Wii do the measurements, it would then say in a chipper little voice...

"That's obese!"

Thank you, Wii.
I wasn't aware I was obese.
You've been most helpful.

But now there's this proposed NEW BMI formula - you can read about it here:

And the formula is a bit more complicated...

1.3 x your weight divided by your height raised to the 2.5 power

Which means my BMI after all the mathematical gymnastics ends up being....


And again, my Wii Fit tells me that I'm obese with that value too.


There's a calculator link in that article where you can see the results of the "old" and "new" BMI formulas. That link is:

So what does this mean, really?

To me - not much.

I'm thrilled when we improve mathematical formulas.


But the BMI - be it the old formula that everyone uses or this new fancy pants one - is a formula.

A mathematical representation.

An approximation.

An estimate.

No less and no more.

In the same way that my weight is only an indicator - and an IMPERFECT indicator - of my health, so is my BMI value.

And so is YOURS.

Remember that.

So what's the takeaway from all this BMI discussion in the news?

Well, if the new formula by this Oxford mathematician is used, taller people will see some change as will shorter people.

But does that TRULY affect anyone's health?

Not in my opinion.

Nope, not at all.

Because I KNOW already that I'm obese.
And minor fiddling with some formula doesn't change that.

If you are within, say, 5 or 10 kilograms of your "ideal" or "healthy" or "normal" weight, then some BMI formula change might alter some numbers but it doesn't change where you are.

It doesn't change anything about YOU.

Only some number that attempts to QUANTIFY your health.

And formulas are limited in their capacity to do that.

There are many other numbers that are useful.
And any good physician is going to employ those numbers as part of the process of assessing your overall health.

Things like your resting heart rate.
And your blood pressure.
And the results of a blood panel.

Yes, your weight is a useful measurement.
And so is your BMI - which is, of course, based on your weight.

But it doesn't tell the WHOLE story.

And mathematical formula changes won't make you healthy or unhealthy.

ACTIONS YOU TAKE will do that.

So TODAY is a great day to take positive, healthy steps to improve your overall health.

Don't you think so?

Nothing's changed.

Eat in moderation.
Eat a diet that is varied and full of the nutrients your body needs.
Hit your daily net calorie target value.
And do a little exercise.
Eschew stupid things like fruit juice fasting and diet pills.
And focus on your long term health.
And be forgiving of yourself when you slip up.
But be mindful about what you put in your mouth each day and the decisions you make.

You can do this.

You are strong.
Strong enough.
Strong enough to succeed in reaching your thoughtfully determined goals.
Strong enough to overcome setbacks and doubt.
You are much much stronger than you might think.

Remember that.

And hey...

Make it a great day!


Member Comments About This Blog Post:
DOTTY7267 2/11/2013 2:25PM

    I must admit I have fallen victim to basing my emotional state/health by what my BMI indicated, just like I had done with the scale. Our relationship has changed slightly, as I no longer have to see what it says to know that I'm okay and doing well. I helps to think of it as just a formula, and not a definition of what you are.

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EFFRAYECHILDE 2/11/2013 10:10AM

    emoticon blog!

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KWEEKWEK 1/31/2013 7:40PM


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BLUESMAN1 1/31/2013 6:59PM

    Your standard BMI is 36.79 a reading which classifies you as obese
Your new BMI is 35.87 a reading which classifies you as obese
Your new BMI healthy range is 132.2 to 178.7 lbs.

That's funny! I wouldn't want to drop down that far. Along with my fat is a lot of muscle. I am going for 200 lbs mabey 195, but that's it.

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SCOOTER4263 1/31/2013 6:09PM

    Dang, Matt. I'm only eight pounds away from moving out of Obese and into simply Overweight, and now you've convinced me that it's not a worthwhile consideration!

Your last couple paragraphs rock, though. Excellent expression of principles. Thanks for the reminder.

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MS_ZENZI 1/29/2013 7:28PM

    I felt the same way when the government changed the healthy weight ranges. About 13 years ago, everyone's "healthy weight" became 10 pounds less than previously set. That number didn't effect my goals then and no new numbers would effect them now. Cheers to you!!

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SAILOR64 1/29/2013 7:14PM

    I love this blog entry.

I have been saying for years, there are much better indicators of health than weight or bmi. Hitting the "magic number" is or should be only a by-product of getting physically fit and healthy.

Great Job.

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ANDY_54 1/29/2013 11:19AM

    When I was in the military they frequently used BMI as the gold standard for proper weight (among other things), but alone BMI is not the end all be all in my book. Funnily enough my BMI with the new calculation is just a smidge higher. So I think what we 'gained' here is another difficult mathmatics problem--is the author a math nerd or something?--to tell me I'm overweight. I kinda get that, you know? On the other hand it also shows I can weigh 114 and still have a healthy BMI, hm approximatley the same weight I had when I was 8. Yikes.

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HEALTHY-SPARK 1/29/2013 10:59AM

    Awesome thanks for sharing!

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FIRECOM 1/29/2013 10:55AM

    I agree. There are a lot of muscle bound athletes out there that can be defined as obese.

If you place all the statisticians in the world end to end, they would never reach a conclusion

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IMAGINE46 1/28/2013 3:07PM

  So true! emoticon

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ANOTHERJEN76 1/27/2013 9:06PM

    The BMI is ridiculous. Last year I did up my son's BMI just to see. I don't remember the numbers off hand but he was almost 11, almost 5' tall and 87lbs. According to the BMI he was borderline overweight which is the most ridiculous thing I've ever heard.

You'd understand if you saw him. He has almost no fat on him. You can see all his ribs. His weight is all muscle and he's perfectly healthy.

And that's the thing with BMI--it does not take into effect where the weight comes from. Muscle weighs more than fat so if you are muscular it's going to screw up your BMI.

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MONIQUE432 1/27/2013 2:16PM

    I love what people are sharing here! I agree with what one person said: If only the medical community would catch on. Guess that is a lost cause though!

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WILDFLOWERMA 1/27/2013 10:50AM

    Yes! Thank you!

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_CYNDY55_ 1/26/2013 8:11PM


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CURVYGURL8 1/26/2013 8:03PM

    I couldn't agree more! Now, if only the insurance companies would catch on. . .!

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CHELLEG10FIT2DA 1/26/2013 12:29PM

    I've never bought into the BMI hype. I think it's ridiculous to think it is a good judge of health. Unfortunately the new formula puts the top end of my "healthy" weight down to 131 from 136. And the low end down to 97!!!!! Unbelievable. I don't buy it but life insurance agents use this BMI calculation to determine health and that really stinks!!!! There should be a more accurate way.

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JEFEIST 1/25/2013 11:48PM

    Lots of wisdom in your blog. Knowing my BMI has not been the best motivater.

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STARSMEMBER267 1/25/2013 5:22PM

    I like what you said. To be honest I was almost rolling on the floor laughing about the Wii. I swear that thing hates me. But as you said who cares. I was so worried about that 0.1 difference that would take me from overweight to average. I don't really think it changed much. Now I have to worry about how close I am to crossing back over. Only 1.3 between me and overweight land. Which is silly.

So.. both the BMI and the scale get a 5 second start. Then I am coming after them and they will not survive if I catch them.


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OVHENDERSON 1/24/2013 1:08PM

    I honestly can't stand the BMI charts (both of them) either. I'm glad the are thinking about the height factor a little more, but that's still not enough. It's still not accurate for anyone who works out, because it doesn't differentiate between bone, muscle or fat weight. A bodybuilding friend of mine laughs at the chart, because he's considered morbidly obese. If you looked at him, you would see that he is totally cut up with a ripped midsection and all. We know muscle weighs 3x as much as fat, so why can't the medical community as a whole just measure their patients body fat % like allied health professionals (i.e. athletic trainers, personal trainers) do? Don't get me wrong, some doctors don't use BMI charts for this very reason, but most of them do refer to a chart on a piece of paper to tell you how healthy you are instead of using their brain and actually taking an real assessment of their patient's body.

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ANGELWINGS71079 1/24/2013 12:46PM

    emoticon blog

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TREE57 1/24/2013 10:57AM

    As if we need the Wii to tell us! HA

Good blog and I totally agree!!!

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MARUKI52 1/24/2013 10:14AM

    Thank you for posting this.

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CICELY360 1/24/2013 9:01AM

  interesting blog

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DRB13_1 1/24/2013 1:17AM

Regarding health, there is a trend to use the waist:height ratio as a better predictor than BMI.
Whatever we can use to see progress, keep us motivated, and establish good habits is the true key!

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ILIKETOZUMBA 1/24/2013 1:01AM

    AWESOME blog!! Thank you for sharing the new formula and for sharing your spot-on commentary regarding the whole concept of quantifying one's health via a single formula. I totally agree with you!

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JAMER123 1/23/2013 11:49PM

    I rarely look at my BMI. I just know where I fall in the figures and go from there. I am looking for a healthier me, not a number which wants me to be bone thin!

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LIBBYL1 1/23/2013 11:01PM


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NEWTINK 1/23/2013 10:44PM

    good and interesting blog .. I dont put much stock in the BMI it is just one measurement based solely on the numbers ... Have a great day emoticon

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ROCKYCPA 1/23/2013 10:38PM

    Remember it is just a number - remember how you feel!

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1MYSTERY_LADY 1/23/2013 10:34PM


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PENNYPACKER3 1/23/2013 10:12PM


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HEARTS116 1/23/2013 9:00PM


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LYNNA1968 1/23/2013 7:27PM


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CLAYARTIST 1/23/2013 6:47PM

  emoticon emoticon

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SHOAPIE 1/23/2013 6:42PM


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MIMIDOT 1/23/2013 6:31PM

    Great blog! Thanks for sharing.

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MARYJEANSL 1/23/2013 5:58PM

  Yes, I don't think much of BMI, don't know what mine is, and don't care. I already know I'm obese also. I have other things to worry about than that particular number.

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SIMOFDIM 1/23/2013 5:17PM

    Well said!

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TERMITEMOM 1/23/2013 5:11PM

    Yep - you can't measure people with just numbers... Great blog!

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IAMAGEMLOVER 1/23/2013 5:07PM

    I was going by my BMI and wanted to reach 120. When I saw my family at Christmas they told me enough is enough. I was getting too thin. According to my BMI I am overweight. Am I going to listen to a family of 25 that care about me or some mathematical equation.? My family. I am now maintaining at 133.2

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ALIDOSHA 1/23/2013 4:57PM

    emoticon emoticon

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BLUE42DOWN 1/23/2013 4:45PM

    As others have said, it can be a good indicator that some lifestyle changes are needed when it is over 30. At that point, it is pretty self-evident (when we're honest with ourselves) that we aren't one of the less-common, super-bulked up body-builders who gets that result even without an ounce of excess fat.

And, using that calculator I had to laugh. I "changed" from 25.81 to 25.53, but it then says my healthy weight range would be 121.9 pounds to 164.7 pounds. I'd have to lose lean body mass to reach that "healthy" low and with only 4 pounds over the high end, I have more than that to lose to get rid of visceral fat deposits and actually be as healthy as I need to be. Good proof that BMI is only useful as a gross estimate of condition.

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DIANNEMT 1/23/2013 4:21PM

    I will say I worked VERY hard to get my BMI to a "good" number but the last 5 pounds really didn't make any difference in my health.

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    thanks for this! It's good to have reminders like these sometimes! I love when my Wii groans as I get on. I don't love that it tells my 6 year old that SHE is obese at 50 pounds. Thank goodness she doesn't know what that word means, yet.

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    I totally agree that BMI is just a number, and probably one of the least useful numbers we're judged by. Kind of like shoe size. It says something about us, but not much. Old BMI 26.46 overweight; New BMI 26.17
overweight. Not much difference.

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JUSGETTENBY42 1/23/2013 2:58PM


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CHARTHESTAR 1/23/2013 2:50PM

    I agree with you. BMI- only take in two aspects. height which can't be changed. the with the more muscular you are it weighs more than fat- so that number can not be any way close to an accurate reading of a persons health.

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DW33412 1/23/2013 2:19PM


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NEWCHINELO 1/23/2013 2:16PM

    It's one of those tools in healthy living!

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