And yes, spreading wide is widespread. But like most things, obesity is not spread equally across social classes. The same survey found that adults with a degree, diploma or higher qualifications were less likely to be obese than those with other or no post-school qualifications. But let's not blame the victims. It's a sad fact that a proper diet is harder to maintain in poorer neighbourhoods, which lack supermarkets and the wide variety of healthy choices they offer, but which have plenty of outlets providing cheap, fattening fast food. And if you're working two jobs, who has time to cook or the energy for exercise?

But your neighbourhood isn't the only problem. In one of the most bizarre scientific findings of 2007, Harvard researchers reported in the New England Journal of Medicine that obesity is "contagious"- that your friends are making you fat. Indeed, your closest friends influence your weight more than your genes or your family members.
The researchers studied 12,067 interconnected people who had participated in the Framingham Heart Study from 1971 to 2003. They organised them by their social networks and found the big "whoa": when a participant's friend became obese, his or her chance of becoming obese increased by 57 per cent (using data from men only, the risk nearly doubled), compared with a 40 per cent chance if a sibling became obese. And if it's a very close friend seen often who packs on the kilos, your chance of bursting your buttons increases by 171 per cent.