Friday, 18 March 2011

Or it might be that your major underlying assumption is rubbish

[trigger warning]

Another piece of terrible BBC reporting (complete with stock "headless fatty" photo), this time about life expectancy and the "obesity epidemic".

The lead paragraph is:

Life expectancy in the UK is on the rise, along with the rest of Europe, despite fears over the impact of obesity, a population expert has said.

In summary: life expectancy has been rising in the UK, mainly because of better treatment for heart conditions. This is a surprise, because as reading the news makes clear, everyone is becoming "obese" and should be dead already.

It can't at all be because - as major population studies in Canada, Germany and the USA have consistently shown - there is no statistically significant link between BMI (the measure of "obesity") and life expectancy.

We are yet to see the impact of a generation of people who have been obese from childhood through to adulthood. We can't predict how that will affect life expectancy figures in the future.

While more individuals nowadays are likely to be sufficiently far above the government-mandated weight that they count as "obese" for most of their lives (and especially now that the government - through the time-honoured technique of "making it up" - is defining more and more children as "overweight"), there are plenty of people who have been "obese" for all their lives, who were in those major studies, and who didn't die at any greater rates than anyone else.

But this argument1 will keep them going on the "fat will kill you" track for a few decades.

At some point historians of medicine are going to look back and show how researchers managed to completely ignore major population studies saying "no effect" in favour of studies that don't get beyond correlation is causation, because they were so convinced of the truth of their main hypothesis that they just ignored evidence against it.

Until then, more terrible public policy and reporting, and more encouraging of hatred against fat people.


1 It occurs to me that this resembles the backstop argument for people when presented with unbeatable evidence of (e.g.) gender or racial inequality: "that is due to discrimination 30 years ago the after-effects of which haven't worked their way out of the system yet; in another 30 years it'll have gone". It's an argument that never gets old.