Trimming the fat off the obesity debate

Sumos vs. Firemen. This happened.

We should always have doubts when the news media claims scientists have conclusive proof one way or another. In part, this is because science does not work that way. Each piece of research is a piece of a far larger puzzle. Often, what the press claim is a major discovery is in fact just a small step in a very long process.

It does not help, of course, that many reporters don't know the first thing about science and have a bad habit of appealing to authority, filing their copy and then heading off down the pub while the subs argue over commas. The problem is, the public don't read many academic journals so rely on scientifically illiterate or alliterate hacks to get their information.

A classic example of this comes in the form of today's news of a 'major study'. This claims to be proof that you cannot be fat and fit at the same time. Alarm bells should ring when the dreaded phrases 'scientists say' or 'say experts’ turn up. The news stories dwell on how 3.5 million people's records were used in the study, but don't mention any complicating factors, like how large samples can sometimes distort data, or the role of systemic bias. (Look up the Bell Curve controversy and see for yourself.)

The other problem here is that the study uses BMI. Now, much ink has been spilled on how unreliable this means of measurement is. But the problem is that doctors seem obsessed with it and do not want to let it go. In part, this is due to it being standard practice, and medics are creatures of habit. But it also coincides with an ideological bias in the medical profession, and bias is an occupational hazard for all areas of research, cutting to the very heart of epistemology.

Of course, even scepticism can go too far. Look at Andrew Wakefield and his MMR scaremongering, which continues to harm children and risk public health to this day. (Not helped by there being a total cretin in the White House who believes in this tosh.) And it is safe to say that science has proved, quite conclusively, that getting hit by a speeding bus is very bad for your health.

The point, however, is not that science isn't perfect. Who says it was? But it needs to be held up to scrutiny and for that, a well-informed, not opinionated, public is needed. Alas, the public are not equipped for this. The press, and our schools, have to share much of the blame for that. The end result is a confused public, and seedy politicians like Michael Gove claiming that we have all had enough of experts.

On the other hand, when one of the researchers says this, alarm bells should still ring loud:

I understand that argument. BMI is crude … but it is the only measure we have in the clinic to get a proxy for body fat. It is not realistic [to use anything else] in a GP setting or in the normal hospital clinic. We have to rely on BMI measurements, however crude they may be.

If you are going to undertake serious research, you need a more precise model than that. Medicine, where the subject has a bad habit of dying if you do not get it right, must be based on a far more exact approach than ‘crude BMI’.

Body fat percentage, plus family and personal health histories, blood tests and fitness are surely far more accurate than the ad hoc BMI measure. Obesity, as it happens, is far trickier and more complex than the usual 'calories in, calories out' rhetoric will allow. 'It sort of works' might pass muster if you are a plumber. But research of this kind has far reaching implications for public health and public health policy. Yet neither the news media nor the public seem to know the first thing about this. Potentially flawed and problematic research is hailed as the final word on debates that still keep on raging. This is irresponsible on the part of researchers, but also on the part of the media, whose main goal, whether they like it or not, is to titillate, not inform.

In the short term of course, what this will continue to do is help further stigmatise fat people. A cynic would say this is the whole point of the news coverage. After all, the public likes to have its prejudices affirmed, and not challenged. But neither scientists nor the press have to go along with this. At the very least, an honest discussion on the limits of data, and the perils of bias, is long overdue.