Tim Cole
speaker
31 appearances
3 recordings
1 series
first heard Aug 2011
last heard Jan 2013
Tim Cole’s voice in public audio — every appearance, attributed to the second.
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Appearances
If you imagine a group of people and you've got their weight and their height, and some people are tall and some are short, but you want to be able to compare the weight of the tall ones and the weight of the short ones,
So you can use a statistical technique called regression analysis to adjust for height.
And so what you're left with is an index which is weight adjusted for height.
Now if you do that calculation, you end up with an index very similar to BMI, and the fact that the power is rounded to two makes it easier to handle.
But there's a fair degree of uncertainty in what the power is, and it's not critical.
Well, it's one of a long line of papers that have been published talking about whether BMI is the right index.
I think he's aware of the deficiencies of BMI, but I don't think his index goes anywhere to addressing those shortcomings because BMI is an imperfect index.
And you can tinker about with the power of height as much as you like, but it shouldn't be expected to do what it can't do, which is to measure fatness, because it doesn't include fatness, it's just got weight.
So BMI can't do better than make a guess, as it were, about how much fat there is.
And of course people's body composition varies enormously, the amount of fat they have varies, and BMI doesn't know anything about that.
So it's a very imprecise index when applied to individuals.
but it is useful when it's applied to populations.
The population does mean that you get a more precise estimate of BMI simply by averaging over large numbers.
There's a question.
Well, the answer is that they are, to some extent, based on health premises...
as understood by Garrow and Webster in 1985, when the world looks rather differently now.
But also, they are a statistical construct.
And trying to draw a line somewhere on that spectrum and say below this cut-off is healthy and above this cut-off is unhealthy, is obviously a rather arbitrary exercise.
I mean, there's a lot of debate now in the States whether people who are overweight
are actually more unhealthy than those who are normal weight.
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