Horizon on fat: a mechanism is not a cause

Last night, BBC2’s Horizon programme discussed “new” discoveries about what lies behind the “obesity epidemic” that’s assailing us. It was a fascinating programme, and did indeed reveal some very interesting things: but fascinating as it was, it was also deeply misleading.

It was presented by a surgeon who began, so the programme told us, with the belief that obesity was a consequence of people eating too much, and exercising too little. People who exhibited such behaviour did so because they were too weak-willed to do any better. Ergo, what was required was some stern talking, possibly the compulsory viewing of “Supersize vs Super-skinny” (well, had it not been on a rival channel), and for those whose wills were not thus strengthened, the reluctant intervention of an already over-stretched NHS to deal with their inevitable type 2 diabetes, and perhaps an opportunity to recoup some of the money by selling voyeuristic clips of yet another stomach by-pass operation in action. The latter probably wouldn’t be very effective, as the market for gruesome shots of implements that “cut and staple simultaneously” would seem already to be saturated. Every time yet another programme turns the spotlight on our modern gross fatness, and what we might do about it, it seems it is de rigueur to include surgeons at this most unattractive pastime.

But the surgeon starring in yesterday’s programme was obliged to confess to an unsavoury attempt to “take the moral high ground” with her simplistic view that perhaps obese people might have some slight degree of responsibility for their predicament. Because she was wrong. It was all down to genetics. Fat people have a “hunger hormone” that is frankly too lazy to make them feel really hungry when its owner is really hungry, and instead merely makes the hapless person feel a bit peckish all the time. On the other hand, obese people have a “fullness hormone” that never gets its act together at all, and never informs the brain that enough is enough. Later in the programme it was revealed just how the brain was responding to all this hormonal misinformation: thin people’s brains were hardly exercised at all by pictures of cream doughnuts, whilst fat people’s brains produced a veritable frenzy of irresistible urges that their rubbish fullness hormone utterly failed to control.

So obese people are between a rock and a hard place. It is truly wrong to hold them responsible. On the one hand their hormonal chemistry is all up the creek, and on the other their brains conspire against their every attempt at self control. The answer? Well, it seemed to be either hormonal pills, or else an odd side effect from the ubiquitous stomach by-pass surgery referred to earlier, which seemed to have the unlikely additional benefit of re-educating the brain.

It was easy to be carried away with the programme’s scientifically certified approach. Except for one rather glaringly obvious point that was never mentioned at all. The human brain has been as it is for a rather long time. The body’s hormonal chemistry has been as it is for millennia. And yet the obesity crisis that we are constantly being told about has only really taken off in the last, say, 50 years. It’s only reached the consciousness of TV producers in the last 20. Thus I can with absolute confidence say that the cause of this crisis is not to be found in endocrinology or in brain functionality, neither of which has suddenly changed in the last half century. A cause and its effects cannot possibly be separated by such an extravagant slice of time. To believe this proposition is to believe that fundamental aspects of our biology, that never bothered our species before, have suddenly begun to do so. Obviously not.

What the Horizon programme so carefully and thoroughly revealed was not a cause, but a mechanism. The cause is much more obvious, and simpler. It is that our Western diet has changed over the last 50 years in very deleterious, but very profitable, ways. At the same time, our level of physical activity has dropped precipitately. What we can learn from yesterday’s revelations is that this sorry state of affairs does not affect us all equally. Some of us are better equipped than others to resist the doleful consequences of rubbish food and physical slothfulness. True also is the programme’s point that resistance is easier for some of us than others.

What would a rational response be? Surely it would be to attack the causes, rather than to fiddle about with the mechanisms, a fiddling about that is bound to bring other unforeseen consequences in its wake. Why don’t we do this? For two very different, but actually strangely connected reasons. We don’t attack the food culture that is causing our fat malaise because too many people make too much money from its continuance. And we prefer drug or surgical interventions in mechanisms to attacking causes because drugs and scientific medicine are also major money-spinners. Not only that, scientists are as seduced by their flashy toys as any adolescent is by his or her iPad, or Android device, or X-Box console. How much more fun to play with an MRI scanner, or wield a tool that simultaneously cuts and staples, than to wonder about the dominance of hawkers of confectionery or fast food? I can still remember my excitement when I first got to use an electron microscope.

Yes, we should be careful to remember that obese people are indeed people about whom we should care, and not fools that we should castigate. But we should also be very wary of those who would locate every problem in genetics or chemistry, and who seek to minimise human volition or responsibility.

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