Do you remember the sepia-tinted days when shopkeepers would give you 5p for the return of an empty fizzy-drink bottle? For me the memory of this early recycling venture excites a flush of shame. As children, our gang would pilfer the glass bottles from neighbours' porches and backyards and stuff our faces with sherbert on the profit. My more hard-faced schoolfriends went farther and would steal full bottles of Tizer from shop shelves, empty the contents down the grate, then return them to the same outlet, smiling innocently, to collect their wages of sin.

Fizzy-pop bottle crime was my instant thought when I read that the Government is considering giving fat people cash or vouchers to lose weight. What kind of crazed, inverted logic is this? Pay people to lose weight and you give them a motive to gain it in the first place. Don't be thin and a loser, folks. Eat all the pies and - wayhay! - it's payday. If history has taught us anything it is that where state-sponsored financial incentives are involved, human beings will find a way to double bluff the system.

We all heard the allegations during the foot-and-mouth epidemic that some farmers were deliberately infecting their livestock to claim the handsome compensation. Or the stories about people nicking M&S clothes just so they could return them sans receipt and take advantage of their generous refund policy. And the theory that some parents in this country push for their children to be prescribed Ritalin, the drug that combats attention deficit hyperactivity disorder, because they will then qualify for the £40 or so a week “attendance allowance” that accompanies it.

Few anecdotes illustrate the point better than one submitted to the letters page of The Times this week about a town in Italy plagued by snakes where locals were paid each time they brought in a skin to the authorities. Guess what? It emerged that people were breeding snakes to trouser the money.

If the Government wants to give away cash, surely it should convey the right message and reward the already thin, the ones who don't eat buckets of KFC and who subscribe to gyms. Otherwise you may as well do something as daft as paying criminals to give up crime. Oh, hold on. Gordon Brown has considered that one before - a plan for troublemaking teenagers to be paid in vouchers, £20 for every week in which they didn't make trouble.

It is fairly obvious that by introducing a system in which one can profit from obesity, one makes obesity a little more attractive. There are plenty of people in this country who fervently believe that disadvantaged teenage girls deliberately become pregnant so that they will land themselves a council flat.

What do the new obesity proposals do other than up those stakes? It's not just any kid you want, girls - it's a fat kid! Feed them Mars Bars and double your money.

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