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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:
PATRICIAANN46 1/23/2013 2:09PM

  emoticon for reminding us that there are a lot of aspects to being healthy.

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FLRED12 1/23/2013 1:41PM


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JIBBIE49 1/23/2013 1:12PM

    Since I'm 63 years old and can remember when people were NORMAL weight, I certainly find the BMI chart to be accurate. It is just that people are so FAT today that it seems off. I remember before 1984 when sizes were REAL, and a woman wearing a Size 10 was a size 10. There was no such thing as a Size 2 or a Size 0, like now, but then women who were a Size 10 were a real size 10 and not a 16 or 18.

If you watch the BBC Documentary on YouTube "THE MEN WHO MADE US FAT" you can understand why we have the obesity issue we do today, and a FATTY LIVER isn't healthy for anyone. A new report came out that people are living 14 yrs longer now, but the health issues during that time will cost the nation Billions.

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KARRENLYNN 1/23/2013 12:43PM

    You're right about the numbers, at best they are guidelines to point us in the right direction. Actions everyday will be more helpful. But I agree with Dollfacedx, I'll still celebrate when I pass a benchmark.

Have a great day!


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JOANNHUNT 1/23/2013 12:03PM

    emoticon emoticon emoticon emoticon emoticon

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ROBINBIRD1014 1/23/2013 11:58AM

  I hate the BMI too. I have been working out for two years faithfully and I am still borderline overweight according to the BMI. I was a size 12 and am now a size 8. I have lost a lot of inches and my waist is below 30". Since when is being a size 8 overwieght?

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SHIMMYSHAKER 1/23/2013 11:14AM

    No one can take away the fact that at one point, size 16 jeans fit me comfortably...and I now have 3 new pairs of jeans that are size 12! Take THAT, BMI Calculation!


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BLUEJEAN99 1/23/2013 11:10AM


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FIT4MEIN2013 1/23/2013 11:05AM

    Great post! I think BMI is one of the MOST imperfect measurements we have. It lists my scrawny-butt granddaughter as obese.

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FROMNDTOGA 1/23/2013 10:37AM

    Great post. We all need to keep the 'numbers' in perspective. Loved the comparison of incredibly fit athletes being on the wrong end of the BMI scale!

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CBRINKLEY401 1/23/2013 10:13AM

    BMI is just ONE tool for helping to measure health, but it isn't perfect. Michael Jordan, at the height of his career, may have had only 5% body fat, but since he had so much muscle mass, his BMI would have put him in the overweight category. NO ONE would have said he was overweight. BMI doesn't tell you your percentage of body fat. Nor does it give any indication of what your overall health is. You can be thin and very unhealthy, or you can be overweight and still be healthy - heart rate, blood pressure, endurance, overall fitness.
If I had to rely on ONE measure of health, I'd rather go by body fat percentage than BMI. It still will say I am obese, but I believe it to be more accurate, and I AM working to get that number lower.

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REGILIEH 1/23/2013 9:33AM


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JANEMARIE77 1/23/2013 9:26AM

    thanks great blog and wonderful info I'm going to check out the new BMI formula with hope

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FROGSNFLOWERS 1/23/2013 9:21AM

    emoticon emoticon

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GOOSIEMOON 1/23/2013 9:08AM


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OFGREENGABLES 1/23/2013 8:13AM

    So true it's the habits that are important!

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MOMMY445 1/23/2013 8:06AM

    such a great blog! thanks for sharing! have a lovely day!

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AMANDACOETZER 1/23/2013 8:04AM


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JENNAAW 1/23/2013 7:50AM

    Love your post. I feel depressed when I find where my BMI is on the chart. I refused to try my friend's wii fit thing because I was told the wii tells you things like "You are fat!" and I would feel pretty devastated instead of being motivated. My resting pulse is 53 and I love running.

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BECKYANNE1 1/23/2013 7:48AM

    Great blog! There are so many other things that can make BMI not so accurate. A good physician won't look at just your BMI. At least my physician doesn't.

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NILLAPEPSI 1/23/2013 7:37AM

    emoticon I needed to hear this today. I'm still obese, but I'm not a couch potato -- not as obese as I have been in the past -- so that has to count for something.

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BESSHAILE 1/23/2013 7:12AM

    so true

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PENOWOK 1/23/2013 7:09AM

    You're right...not a difference worth noting!! It also bug s me when the wii yells at me for not weighing and measuring more frequently! HA!

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SANDYCRANE 1/23/2013 7:04AM

    I am sure there are a lot of people with acceptable BMI's whom are not healthy. At work people with high BMI's and CDL's had to get physicals and get tested for sleep apnea. What next.


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CHERYL_ANNE 1/23/2013 7:02AM

    Best comment regarding BMI (from

'Your BMI has absolutely NOTHING to do with your body composition It only factors in your height and weight. It will give you the same reading if you're made of 180 pounds of pure muscle, or 180 pounds of pure Cheetos.'


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KATHIC2 1/23/2013 6:39AM

  Well said and insightful!

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GRAMPIAN 1/23/2013 6:24AM

  You're right! emoticon

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NCSUE0514 1/23/2013 6:18AM

    It's JUST a number.

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TRYINGHARD54 1/23/2013 5:53AM

    BMI. someone made that up because they had nothing better to do.. everyones body is different... We all know how good we feel when we lose weight. I dont need a BMI to tell me that..

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SHERYLDS 1/23/2013 5:51AM

    Thanks for your outlook...I agree BMI is just a number.
But all health numbers are just targets to aim for.
Without a number, it's hard to determine how you're doing

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LIFETIMER54 1/23/2013 5:47AM

  emoticon emoticon

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GLORYFB80 1/23/2013 5:39AM

    Well, I don't need a BMI to know that I'm obese, don't need the scales to tell me either . . . I know it by how I feel and look!

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TINAJANE76 1/23/2013 5:34AM

    I completely agree with BREWMASTERBILL on this one. If you're in the obese category and carrying a lot of body fat, lowering your BMI can be a useful tool. Once you get into the overweight or healthy category, measuring body composition paints a more accurate picture of your overall health and progress. There are exceptions of course--if you're a bodybuilder or professional athlete, for example, you can have a very low body fat percentage but your weight may put you in the obese category. Or if you've never done a lick of exercise in your life, you can have a healthy BMI but an unhealthy body fat percentage. That's why I think taking a broader perspective and looking at how all of your numbers fit together is the way to go. I have a healthy BMI, a healthy body fat percentage, a waist well under 35", a clean bill of health from my last physical and bloodwork panel and scored above the 70th percentile in all areas on the last Army Physical Fitness Test I took. All those things together spell good health to me and are what I strive to maintain rather than just staying focused on a specific number on the scale alone.

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SPARKLISE 1/23/2013 5:06AM

    emoticon emoticon

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LRSILVER 1/23/2013 4:42AM

    I agree.

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MICKEYH 1/22/2013 10:47PM

    When I started my health journey, according to my BMI, " I am obese." To me it sounded very harsh and surprised the fact, "I am obese." In a year later, With my hard work and patience, consistency, I've lost 35 pound. I think I looks good on some of the recent pictures. (^^) But my BMI still said, I am "over weight." This BMI thing is not very friendly and is very discouraging. But because of that, I have made new determination to beat this BMI guy. Lol))

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BOGUSANNIE 1/22/2013 8:08PM

    BMI is simply a tool to help you gauge things....seriously if I was a body builder it would make me obese you have to take it with a grain of salt and factor in other tools.

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DOVESEYES 1/22/2013 7:26PM

    Like most things BMI is just a 'guideline', we do need them but it's unhelpful if we take too seriously the info.

Better- how do your clothes fit? Are you making a majority of right choices for exercise, eating, emotional concerns?

Are you continuing to learn from Sparkpeople quizzes, info, recipes etc what are healthy choices? When you need to adjust your food, exercise etc are you making small changes or going overboard.

Balance I guess is what I'm getting at. "The roundabout not the see-saw"

Thanks Matt

Comment edited on: 1/22/2013 7:27:11 PM

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CAKEMAKERMOM 1/22/2013 7:23PM

    Just one more number to deal with. Maybe I should just move to the moon, that'll solve my bmi problem. emoticon

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HOLLYM48 1/22/2013 6:53PM

    emoticon emoticon emoticon

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PAULKNUTH 1/22/2013 5:52PM

    Last time I was at the Dr. - he looks at the chart and says to me - You need to lose some weight. You think Doc? When does he get an upgrade?


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KABMPH 1/22/2013 4:02PM

    I really struggle with the concept of BMI. I work in the field of public health and even though it's used, generally we are aware that it's a flawed concept. (I don't use it professionally - not quite my line of work.)

However, this new BMI table seems to give a wider range of what is "healthy" and I worry that it's giving us a false sense of what is normal. That is -- given that the weight of the world is growing, are they loosening the belt (so to speak)/changing the parameters on what the range of healthy is to suit the population?

My question indicates that I "believe in" BMI more than I want to.

And even though this is not scientific at all, Self Magazine (ha!) has a "happy weight" calculator that, for me at least, is in the healthy BMI range. Weirdly, what they say is my happy weight is my actual weight.

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JULINA4 1/22/2013 3:49PM

    Great post! You're right - if my BMI goes down, it doesn't change who I am or what shape I'm in at all. Just like if I eat a brownie in my closet every night and don't tell anyone or track it, it doesn't change that I ate those brownies.

Make it a great day!

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BROOKLYN_BORN 1/22/2013 12:36PM

    Not much change: 21.79 to 21.88
I still have a 40 pound range for the healthy interval.
That's a big range and I'd like to stay smack in the middle of it.

Regarding numbers, none of them by themselves tell the complete story, so I tend to discount anyone who claims that any one measure is the only one to use. Personally, I think there are valid aspects to all of them and I try not to only rely on the one I look best in.

As for insurance companies, it's more about their bottom line then concern for our health. They could take any of those measurement methods and base rates on them that would penalize people. Just one more thing they do, like those "pre existing conditions"

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HEALTHIERKEN 1/22/2013 12:23PM

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

Don't you think so? "

Absolutely and completely! Good blog. Thanks : )

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BODDHISATTVA123 1/22/2013 12:22PM

    Thanks Matt!

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INTHEGAP 1/22/2013 12:19PM

    Matt, thanks for my goodie. :D I could not agree more with this blog. I only wish I could make myself feel the same about the scale ~ but, I'm working on it. emoticon emoticon emoticon

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CELIAMINER 1/22/2013 12:10PM

    I don't hate BMI. It's just one more tool.
Old: 23.08
New: 23.17

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HOLLYS_NEW_LIFE 1/22/2013 11:50AM

    New or old, I hate the BMI... PERIOD!

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BLUENOSE63 1/22/2013 11:39AM


Can't stand that little obnoxious Wii guy and his little voice saying "You are overweight". I just tell him right back "Yeah and you have a big head"...mature right but it makes me feel better somehow!

I know for myself, I am extremely muscular and need to be to do the Triathlons I do each year but technically I am overweight but my response is "who the hell cares"

Go by how the clothes fit, what your pulse is, your choles. levels

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