Any MPs who still doubt the prevalence of obesity in Britain's over-fed, couch-potato society could have had their body mass index (BMI) checked yesterday at Cancer Research UK's stall, handily located between the Commons coffee shop and restaurant.

Gold stars on the board showed how many were overweight or obese. There were quite a lot of elected fatties, representative of a country where two-thirds of adults (one third of children) are heavier than is wise. That "obesity is the climate change of public health" is now a cliche.

But what to do about entrenched lifestyle habits? The government's "healthy weight, healthy lives" plan, outlined yesterday by Alan Johnson, attracted modest plaudits of the not-far-enough variety.

Why are ministers so afraid of the food industry and the supermarkets, all of which resist a single form of effective labelling for their dodgier money-spinners, experts wonder?

Yesterday's faint praise was offset by loud raspberries from Andrew Lansley, the shadow health secretary, about failed and recycled targets under Labour, public health budgets marginalised and trimmed. John Major's government set a target to cut obesity as early as 1992.

It did not become a Blair-Brown priority again until 2004, after a decade of steady growth in the nation's waistline. Not enough has been achieved since, especially in imposing a uniform food label. On current trends obesity will cost the economy £60bn by 2050, not to mention a lot more cancer, diabetes, heart attacks and strokes.

No one mentioned sexual health yesterday, but Norman Fowler's safe sex campaign on Aids-HIV in the 80s remains a benchmark success, in urgent need of repetition. After all, all the bad health charts show it is the poorest who suffer most.

Labour's public health record is not all gloom. It has taken decades to change people's attitudes and behaviour towards drink-driving and, more recently, smoking. It has happened as government-imposed restrictions have moved alongside evolving public opinion. School food (thanks, Jamie) and five-a-day fruit and veg habits have also improved.

The truth is that eating is harder to tackle than smoking. It is more complex, impacts on more aspects of our lives, society and the economy. One day the media is supportive, the next it attacks the nanny state. GPs can be pretty feeble too.

One turning point towards the smoking ban was research that upheld the dangers of passive smoking, says Jessica Allen of the IPPR. Might not that idea that fatty habits (and genes) are passed on to the kids similarly make people face up to the need to lay off the burgers and pies?