Being a bit fat can be healthy. But the medical profession doesn’t want us to know

A GP called Malcolm Kendrick has written a book about politically correct manipulation of medical data – and has cropped up in the Independent highlighting the medical profession’s unwillingness to share research suggesting that being a bit fat makes you live longer. Here are two key paragraphs:

Despite the fact that study after study has demonstrated quite clearly that ‘overweight’ people live the longest, no one can bring themselves to say: ‘Sorry, we were wrong. A BMI between 25 and 29 is the healthiest weight of all. For those of you between 20 and 25, I say, eat more, become healthier.’ Who would dare say such a thing? Not anyone with tenure at a leading university, that’s for sure.

In truth, this discussion should not quite stop here. For even when we get into those with a BMI greater than 30, those who truly are defined as ‘obese’, the health dangers are greatly overestimated, mainly because of the widespread use of what I call the statistical ‘clumping game’. Obesity researchers are world-leading experts at the clumping game. In most studies, the entire population is divided (‘clumped’) into four groups: underweight, normal weight, overweight and obese – obese being defined as a BMI of 30 and above. That means those with a BMI of 31 are clumped together as part of a group which includes those with a BMI of 50 – and above. What does this tell us about the health problems of having a BMI of 31? Well, absolutely nothing.

Kendrick isn’t talking about the falsification of data – the findings are pretty clear. But they’re being presented in a way that deliberately obscures statistics suggesting that slightly tubby people live longer than people who aren’t overweight.

Why? I suspect health professionals are worried that this conclusion – which seems totally counter-intuitive after decades of warnings about weight – undermines the fight against obesity, which is important, since obese people die younger. It ‘sends out the wrong message’. Well, I’m sorry, but that’s not how science should work. Inconvenient facts are often the most valuable ones, since they force us to do our own thinking.

If the NHS is spending millions warning its patients not to enter a ‘danger zone’ of a BMI of 25-30, that’s troubling. Carrying a few extra pounds is dangerous if it’s the beginning of weight gain that leads to serious obesity (as Kendrick says, the risks of mild obesity are less than we’re led to believe). But if your body mass sticks at 28, then you’re actually in a ‘safe zone’.

The methodological tricks that this article describes have an ideological flavour to them. No surprises there. In many fields of research, there’s a temptation to obscure data that challenges the consensus of bien pensant lobby groups. I don’t want to take sides in the battle over climate change, but remember the way the University of East Anglia was caught out trying to gloss over historical changes in temperature that didn’t fit its thesis?