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“So short people are misled into thinking that they are thinner than they are, and tall people are m

Thursday, January 24, 2013

This made my 5'10" self feel a little bit better:

Mathematicians found the formula used to calculate body mass index (BMI) has made tall people more overweight and those vertically challenged not fat enough.

They argued it did not take into account a person’s weight tends to grow with their height, giving taller people more room to bulge.

Consequently Prof Nick Trefethen, a leading mathematician, has devised a new formula after finding the current BMI divided weight by too large a number for short people and by too small a number for tall people.

“The NHS relies on the BMI pervasively in all of its public discussions of obesity,” he said.

“We deserve an explanation of what justification they have for using this formula.
“BMI divides the weight by too large a number for short people and too small a number for tall people.”

He added: “So short people are misled into thinking that they are thinner than they are, and tall people are misled into thinking they are fatter.”

The BMI formula is used by doctors to work out if someone is overweight or obese and so at risk of problems from high blood pressure to heart disease.

It is traditionally calculated by dividing a person's weight in kilograms by their height in metres squared with the aim of giving a measure of an individual's body fat.
But this assumes people scale up according to a model of growth, in which they get taller more quickly than they bulk out.

A BMI of between 18.5 and 24.9 is normal, less than 18.5 is seen as underweight while 25 to 29.9 is considered overweight. A mark of 30 or above means a person is obese.
Prof Trefethen started investigating the problem after realising conventional BMI calculation methods failed to take into account that taller people tended to be bulkier than those who were smaller in height.

He found short people were misled into thinking that they are thinner than they are and tall people are misled into thinking they are fatter.

For those who are 150cm tall [five feet], the new formula would add a whole BMI point, enough to topple people lurking on the borders of the "normal" weight into "overweight" territory and a similar number would become "obese".

Those of 180cm or above (six feet), lose a BMI point. Only those of average height (170cm) will remain the same BMI.

The mathematical formula was devised by the Belgian scientist Adolphe Quetelet in the 1830s. But the professor insisted his formula was far from simply an academic exercise.

“BMI is only one of many factors and inevitably not everyone will fit the standard pattern,” he said.

“We know that BMI is a good indicator of population level trends, but not always a good indicator at an individual level."

Member Comments About This Blog Post:
WHOVIANGIRL23 1/28/2013 1:00PM

    I'm still fat!

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LISA_SUMNER08 1/28/2013 12:30PM

    Did NOT help me! Ugh! I'm 5'4".

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SSBROWN10 1/26/2013 2:10AM

    So I just need to grow another foot and a half....

Kidding. Very insightful article and according to article, I am average height (5'6) therefore my BMI won't change...aaaaawwwww.

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CAGMUAHFO2 1/25/2013 3:40PM

    emoticon I'm 5' I'm struggling as it is. emoticon

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SHRINKING_SARA 1/25/2013 2:52PM

    I'm so excited by this because I lost 0.7 points... putting me just 0.5 points away from "normal"!

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BROOKLYN_BORN 1/25/2013 2:22PM

    It didn't make any difference for me at 5'6". Not even enough for my DH to use as another excuse not to lose some weight.

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LOLATURTLE 1/25/2013 2:13PM

    Interesting! I only lost a wee bit off my BMI, but it does change the weight I need to get to in order to be in the "healthy" range by about three pounds, which is interesting. The "new" top of my range weight sound much more achievable and maintainable to me.

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BRADMILL2922 1/25/2013 2:00PM

    Good news for us that are 6'7"! I'll take it!

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EMMAEKAY 1/25/2013 12:49PM

    Interesting! I've always thought I looked a little trimmer than my BMI suggests, and my body fat percentage backs that up.

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REVIVED 1/25/2013 10:03AM

    I'm 5 foot. This doesn't help me at all! Boo.

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NIKKICOLE83 1/25/2013 8:44AM

    This doesn't change my BMI much at 5'9 1/2 but I agree that my muscular bulk is not the same as someone who is 5'4". But I do benefit from my height because at a size 16 I look a lot more trim than a person five inches shorter wearing the same size.

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AMCLELLAN 1/25/2013 8:24AM

    I lost 1.1 pts. on the new scale. I'm 6ft tall so this really does make a difference for me.
Thank You for Sharing!

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ADARKARA 1/25/2013 8:04AM

    I lost 0.72 points for my height, which doesn't mean a whole lot in the grand scheme of things, but it's nice to know I'm no longer getting screwed by the calcs!

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ADZY86 1/25/2013 7:15AM

    At 5ft10 I'm really glad to hear this. I don't really go by BMI generally anyway, but it's still nice to know that I don't need to go skeletal to be 'normal'!

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CAMAEL100 1/25/2013 4:58AM

    Unfortunately I am average as well so no joy for me!! I always think though that I am not over weight, I am under tall!

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AHTRAP 1/25/2013 2:56AM

    Guess I've average enough that their differences don't alter my numbers more than 0.1 at any weight. Good to know that; I can go on (more or less) ignoring the BMI numbers.

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LEIAWINS 1/25/2013 2:15AM

    gee... unfortunately I'm very average.. sigh!!! No point gained nor lost!

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PRIMA_DONUT 1/25/2013 2:07AM

  This article made me feel so much better about my 5'10 frame!

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