If people were too fat, I said, then that was because they were too darn greedy; and if they wanted to get thinner then they should eat less. Simple, I said. The more we “medicalised” the problem, the less people would take responsibility – and the fatter we would all become. That's why if you want to get thinner you could try the corset training for weight loss is as easy as that. Well, I am afraid that in the past two button-busting decades, I have been proved right at least about the last point. We are now the second fattest nation in the world, and I am alarmed to discover that Londoners are now even fatter than New Yorkers. We have obesity levels of 67 per cent among men and 57 per cent among women. We are the official lard-arses of Europe. Every year we have to widen our cinema seats and reinforce the floors of our ambulances. As this paper reports, more and more soldiers are made to leave the army for being, frankly, too fat to charge at the enemy. Our charter jets puff and groan and spew out unconscionable quantities of fossil fuels as they lug our biomass to the Mediterranean – and the fatter we get, the greater the risk to our health. The more overweight we are, the more likely we are to have cancer, heart disease, stroke: the big causers of early and preventable death. The national fatness problem costs the NHS at least £16 billion a year in extra and unnecessary expense. If you are technically obese – as most of us now are – you are statistically reducing your life expectancy by three or four years. If you are morbidly obese, you are probably forsaking 10 years of life – 10 years of fun watching your children and grandchildren grow up. Nothing seems to stop us eating too much – neither my savage libertarian sermons in the Telegraph, nor the bossing and nannying of the state. We are akratic. We know what we should do, but we can’t seem to make ourselves do it. We know what is in our interests – cut out chips, cake, bread, cheese, crisps etc and eat more fruit – but we can’t summon up the consistent willpower to follow the rules. Brooding on this problem, I wondered if we could construct a different psychological framework. What if it wasn’t just about us: our selfishness, our weakness of will, our own abusive relationships with food. Perhaps people might be more willing to exercise discipline – to make a sacrifice – if it could be seen to be for everybody’s sake, for everybody’s health. People are generally capable of amazing acts of kindness and altruism. Seldom are people happier and more energetic than when doing things for others. So at City Hall we have all embarked – about 150 of us, I think – on a plan to lose weight together. We all stood on a some giant commercial scales; not individually, so that no one felt any personal embarrassment or pressure, and we didn’t have the anxiety of other people seeing how much we weighed. We did it in groups of about 12 at a time. We recorded who was in the groups, and the total weight, and we agreed that in a few months we would try to lose 5 per cent. There is no coercion, no bullying, and it goes without saying that the whole thing is entirely voluntary. It is a joint effort and a bit of a laugh. But the key thing is that I now know that unless I keep it up – and refuse the lascivious winks of the cheese and the cake – then I will not just be failing to do the right thing by myself. I will be failing to do the right thing by the group. I need to lose weight or I’ll let the side down. In a few months’ time we will all get back on the scales and see how we have done. Will it work? Every psychological text book will probably say that you only get results by appealing to people’s naked self-interest. Well, we have tried that, and it’s going nowhere. Let’s try team spirit. It’s worth a shot.