Public health is rightly the government's business. But it is not just the headline issue of smoking on which radical action is urgent. Just how big the general problem has become - and how much there is to be done - can be illustrated by the issue of obesity. Here is a condition which has tripled since the 1980s, generating a rapid increase in heart disease, cancer and diabetes. Unless current UK trends - the fastest growing in Europe - are reversed, half of all British children could be obese by 2020. If that happened, the long lengthening of life expectancy would go into historic reverse.

It is now 10 years since Sustain, a better food and farming campaign, first appealed to the food industry to show more responsibility - an appeal echoed by medical colleges, MPs and the chief medical officer - yet our food is still saturated with too much sugar, salt and fat. Currently the industry is spending £740m on advertising, compared to a mere £7m by the government on public health messages. At the weekend Whitehall suggested ministers would be getting Ofcom, the broadcasting regulator, to negotiate a voluntary ban on such adverts before the 9pm watershed or face a legal ban. By Monday, it was not just the food industry that was digging in its heels, but Ofcom. A ban was not necessary, it claimed, and children's programmes should be protected. So much for the industry cooperating. Even the regulator seems to have been captured.

The biggest threats to health - alcohol, tobacco, inadequate exercise, poor diet, unsafe sex - have been known for years. But there has been a lack of action. A green paper on public health was one of the first initiatives of the newly elected Labour government in 1997, but it is a pity we have had to wait seven years for the white paper. It includes some much needed reforms, but ministers still find it easier to focus on treatment rather than tackle prevention. The boost to sexual health services, for example, was needed; but so was a change in sex education in schools. An extra £1bn for school sport deserves applause. But the biggest disappointments are the failure to deal properly with the two biggest causes of premature death: alcohol and tobacco. Physicians rightly complain about alcohol's low profile in the paper and an inadequate tightening of the advertising regulations. Tobacco controls were stricter than forecast, but by not opting for a total ban in enclosed public places, the plan will inevitably widen health inequalities. A health secretary who wants to narrow such gaps would be sensible to think again.