Body Mass Index

Are Government statistics flawed?

11 messages
22/07/2006 at 14:51
For decades the recognised system for defining someones height/weight ratio has been the Body Mass Index, (BMI). From this a person is annotated: underweight, normal, overweight, obese, morbidly obese. This system is used from doctors to insurance companies, who may be trying to sell you one of their products. It also defines statistics that the Government use to inform us of the countries overall state of health.

However, I feel that this system is outdated and flawed. The system is based on your overall weight and does not take into account factors such as muscle mass. My friend is 5' 11" and weighs 14.5 stones. Under the BMI system he is obese. What it does not say is that he has a body fat percentage of 8%. The majority of his weight is muscle. So how on earth can he be obese? But on some file in some government office, that is exactly what he is and will show up on these 'offical' reports as such.

Isn't time the Government looked long and hard at updating this system and maybe we wouldn't be living in a state of paranoia that the media is currently stuffing down our throats?
22/07/2006 at 14:56
I'm told by a doctor that BMI doesn't apply to athletes, and I think many of the websites that offer BMI calculators make this clear.
22/07/2006 at 14:58
this article, miss the first three paragraphs, or so, they're a bit pointless and dull, questions whether we should think of there being a link between weight and health, at all.
22/07/2006 at 16:38
It's normally assumed that muscular athletes with a high BMI but a relatively low body fat percentage are "healthier" than sedentary people who have the same BMI but a higher body fat.

Is there any evidence that this is true, or is it just an assumption?
22/07/2006 at 17:13
That's the question the link raises isn't it.

I don't agree that the BMI index needs updating though - it's just a guide which we all know doesn't take account of individual difference but is meaningful at a population level.
22/07/2006 at 17:21
Thinking of non-athletes with a high BMI for a moment, there is apparently little doubt that there's a link between obesity (BMI>30) and high blood pressure, diabetes, raised cholesrterol etc. However, I read a great article in Scientific American which quoted a lot of good research showing that obese Americans often had a better health outcome than less overweight Americans. The reasoning seemed to be along the lines that obese people get screened more and their problems get detected earlier and treated more vigorously as a result.
The Evil Pixie    pirate
22/07/2006 at 17:30
My BMI is 29.5
I have low blood pressure
no sign of diabetes
low resting hr

I'm a very slow runner
22/07/2006 at 19:34
I'm pretty sure this whole thing is being looked at. I remember hearing that the whole BMI thing was being ridiculed as a vast majority of professional rugby players would officially be obese
22/07/2006 at 19:50
And maybe professional rugby players ARE obese, with the same long-term health risks as non-athletes with a BMI in the "obese" range, in spite of their sporting abilities. We don't have enough evidence to say for certain that BMI is irrelevant in some populations.

There's some evidence from the UK too that people with a BMI in the "overweight" range (25-30) have better health outcomes than those with a BMI under 25, even after excluding people who are skinny because they are ill.
22/07/2006 at 21:05
At the moment I have a bmi of 24.6.
And according to a little hand held bioelectrical device a bodyfat percentage of 29.0
I still get acused of being thin.

But I know that I am fatter than I usually am at this time of year.
I tend to vary by about 7lbs winter to summer. This year I have kept my winter fat.
22/07/2006 at 22:27
The Wikipedia article on BMI is well worth reading. It gives a good explanationof the limitations of using BMI as a measure of non-sedentary people. - it's too late for me to be doing hyperlinks.

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