Wednesday, 17 February 2010

Fat chance

They mean 2020, of course. Is the sub-editor of The Times on holiday, or is this headline a subtle satire on the soothsayers of public health, who were making drastic predictions about 2010 a few short years ago?

Predictions like this:

England to have 13m obese by 2010

More than 12m adults and one million children will be obese by 2010 if no action is taken, a report by the Department of Health is predicting.

Did that happen? Of course not. Back then (2006) the big headlines were about childhood obesity, which was supposed to rocket up. In fact, this happened:

It went down. This epic fail has been implicitly recognised by the new forecasters, who say:

“Unlike the recent report on child obesity, which showed some indications of a plateauing or at least a significant reduction in the rate of obesity..."

That sentence is the wrong way round, surely? Whatever. The point is that childhood obesity has fallen and was already falling when the public health doomsayers were warning of the sky falling on our heads. But hey, everyone makes mistakes. Let's change the subject...

"...the future projections for adults are less optimistic.”

Well, naturally. Show me an optimistic projection for anything to do with obesity and I'll show you a public health professional heading for demotion. Having cocked up the childhood obesity predictions, they are now focusing on adult obesity which has risen, albeit by a lot less than was predicted. It means they lose the think-of-the-children aspect, which is politically inconvenient, but nevermind.

The study, led by Professor Klim McPherson, of the University of Oxford, uses figures from 1993 to 2007 to predict future levels of obesity in England. It says that about 41 per cent of men aged 20 to 65 will be obese by 2020 and 40 per cent will be overweight; 36 per cent of women will be obese and 32 per cent will be overweight.

As the Department of Health recently - though quietly - announced, male obesity is 24% and female obesity is 25% (see here, p. 14). This is significantly less than the 33% and 28% predicted in 2006, but it is significantly more than the 16% and 13% recorded in 1998.

Leaving aside issues of data collection, that is a pretty big rise in obesity. In ten years, an extra 8% of men and 12% of women have become obese.

The new projection says that a further 17% of men and 12% of women will become obese in the next ten years. Altogether, they say, a total of 81% of men will be overweight or obese by 2020. Any projection that suggests that fewer than 1 in 5 men will be normal (or under) weight in ten years time should raise eyebrows.

And how do they get to these figures? By using "figures from 1993 to 2007". But the past is no guide to the future. How do we know that the biggest rise hasn't already come and gone? Buried away in the Health England Survey is an indication that this is exactly what has happened (emphasis mine).

Between 1993 and 2008, there has been a marked increase in the proportion who were obese. This proportion increased from 13% of men in 1993 to 24% in 2008 and from 16% of women in 1993 to 25% in 2008. However, the rate of increase in obesity prevalence has been slower in the second half of the period than the first half, and there are indications that the trend may be flattening out, at least temporarily.

You can't just extrapolate from previous figures. The childhood obesity figures show us that. Contrary to received wisdom, obesity is not a disease. It is not contagious and it won't spread inexorably. A recent study in the Journal of the American Medical Association found that obesity in America has not increased at all since 1999. 

The JAMA study is important because it shows that obesity flat-lined at 32.2% (men) and 35.5% (women). The new British projections give figures of 41% (men) and 36% (women). Is it really likely that the UK is going to overtake the fattest country in the world - by quite some way in the case of men? Isn't it much more likely that, as with children and as with the US, the 'epidemic' will peak long before it gets to that point?

Public health projections are, quite simply, worthless. Whether the issue is swine flu, smoking or obesity, they are never anything but guesses (how could it be otherwise?). They are intended purely for the purposes of lobbying. Nothing else.


TheFatBigot said...

Once more than 50% are obese, are they obese or normal?

Anonymous said...

Great analysis Chris. Why doesn'the Times employ you? What do their journalists do all day? They are not churning out multiple articles. Why not spend some time on making them of value to their readers?
Very good point GTB. Obesity is defined to be the level at which statistically ignorant empire building medics can write lots of nonsense and at which drug companies can profit by "treating" it.

Anonymous said...

I'm not sure if the same thing happened in the UK, but here in the US, they (the NIH, I believe) simply lowered the bar and what weights are considered "obese" relative to height.