The Tory leader David Cameron believes in telling it to us straight: "We talk about people being 'at risk of obesity' instead of talking about people who eat too much and take too little exercise," he says. "We talk about people being at risk of poverty, or social exclusion: it's as if these things – obesity, alcohol abuse, drug addiction – are purely external events like a plague or bad weather."

He says: "Social problems are often the consequence of the choices that people make."

In a response, health secretary Alan Johnson agrees that we should be told we are too fat but more diplomatically. "Vilifying the extremely fat doesn't make people change their behaviour," says Johnson in a speech to the Fabian Society, extracts of which appeared on Cif last night.

One way of toning down the "personal responsibility" message is to stress that it is not people's fault. His suggestion that obesity is the natural outcome of poverty would have puzzled earlier Fabian audiences. But overall it is true that these days in Britain that the rich are thinner than the poor.

He makes the more general point that "the fact that for an increasing number of people, weight gain is inevitable and largely involuntary as a consequence of exposure to a modern lifestyle". But it isn't "largely involuntary". I walk a lot, which is good. I drink too much alcohol, which is bad. I could take the bus more and be fatter or drink less and be thinner.

Those are the sort of mundane judgments most of us make on a daily basis. For some it may be more challenging. Johnson didn't address the question of addiction. I was interested by Peter Hitchens's comment in the Mail on Sunday recently: "Lord Laidlaw says he is a 'sex-addict'. Actually he's just a dirty old man, in the same way that alleged 'bulimic' John Prescott is a greedy fat pig... There's no such thing as addiction."

I think Hitchens is wrong and that those with an addiction should be regarded as a different category. But for the rest of us it is a matter of personal choice. Being told very politely to diet by Alan Johnson, rather more firmly by David Cameron or rather rudely by Peter Hitchens and Rod Liddle is unlikely to make much difference.

Johnson's gimmicky "obesity strategy" seems doomed to fail. ("I have written to 220,000 local activists ..." he says. Groan.)

This is not to say that government is irrelevant. Children used to play in the streets more before many of the streets were replaced by tower blocks. Schools used to have far more competitive sport. Teachers stop bothering with school trips because Ofsted complain about them not completing a risk assessment. Children find opportunities for exercise closed off by the torrent of "risk-averse" health and safety regulations from the nanny state – which now has the audacity to criticise them for being coach potatoes. Jamie Oliver is right to highlight that the state should sort out what it feeds children at lunchtime before denouncing what parents feed them for supper.

Johnson's approach all sounds a bit too grand. At my local park, Normand Park in Baron's Court in west London, metal ping pong tables have just been introduced next to the playground. They have proved a hit with teenagers turning up with their bats and balls. That is the answer to obesity, not Fabian Society lectures or obesity strategies.