It would be lovely, of course, if the sight of a reality TV star bursting out of a bus was to inspire the children of today to drop their Mars bars, and their fries, and their burgers, and their Xboxes and beg their parents to let them get up early and do 300 laps before a nice bowl of buckwheat muesli.

Fingers crossed and all that, but really. I wanted to be Olga Korbut, and then Bjorn Borg, but without getting off the sofa, obviously, and I come from a family whose male members actually did some sport as well as watching it, but the last time I did any with any enthusiasm (‘music and movement’ if I remember rightly) was at about the same time they put a man on the moon.

Let's hope that the rapturous welcome home for ‘Team GB’ (a name almost as embarrassing as that bus) will be a sign that a thousand, nay, a million, sporting flowers will duly bloom, but let's not get too carried away either. The sobering reality (that's reality as in empirical fact, not as in TV genre selected to represent centuries of British culture to the entire world) is that Nation GB is set to win one medal that wasn't even on the list. Yup, it’s on course to be gold medallists in obesity.

Every day, new facts emerge. Airline seats, and coffins, are being widened. The NHS is on its last, flabby legs. Type 2 diabetes is set to trigger mass amputations. Never mind our carbon footprint, we'll soon be squashing the planet into a giant pancake — and then, no doubt, trying to eat it.

So, what do we do? Get supermarkets and fast-food outlets to put labels on fattening food saying that it's fattening. Run government ads telling us that fattening foods will make us fat.

Get David Beckham, perhaps, to tell us that fattening foods will make us fat. (Which, presumably, is why his wife eats hardly any food at all.)

The trouble is that the war on obesity is like the war on terror. It's slippery, and wobbly, and elusive, like a great, big jelly. You can staple people's stomachs, lock them in at lunchtime and lecture them until the cows come home and collapse in front of the telly, but if people want to eat themselves to death, they will.

Unless, perhaps, you're very clever. And the human mind can be very clever.

According to a new study from Harvard, hotel cleaners doing hard, physical work for eight hours a day believed they were getting no exercise at all. And their health — as measured by weight, body fat, blood pressure, etc — reflected this conviction. Half of the group were then told that they were, actually, getting a lot of exercise, and the other half weren't.

Four weeks later, the group who now felt virtuous were found to be significantly healthier than the ones who didn't. Mind over matter indeed.

Quite what this means for our massed potential medallists isn't entirely clear.

It would, presumably, be better to move a bit more and eat a bit less.

But maybe if we can persuade ourselves that a waddle to the fridge is as good as an afternoon's angling and that a Mars bar is as healthy as a carrot then we'll see the nation's waistlines shrink. Or maybe it's all just nonsense and we won't.

But one thing is clear. We can fiddle while Rome burns, we can lecture and hector and label, but this battle, like all battles that have a hope of being won, will start with the mind. (Cholesterol-ridden, adipose-wrapped hearts will follow.)