Leading article: A nation running to fat

The rate of increase in obesity in this country is too fast to be ignored. The official figures to be published this week, which we report today, reveal a pace of change that has serious consequences for the health of the nation. This is not a matter of stigmatising the fuller figure. While some might argue that the Department of Health's definition of clinical obesity is set too low, there can be no argument that too much body fat is unhealthy - and there can be no argument about the direction and pace of change.

Whether or not the proportion of the population that is unhealthily fat will be approaching one-third by 2010, as the Department of Health predicts, the fact is that the current rate of increase in the incidence of obesity - including the most extreme cases - is frightening. It has alarmed the medical profession, and it may be that the early data on which this week's figures are based prompted the Prime Minister to devote much of his speech on public health last month to the subject.

This can no longer be regarded as merely a matter of personal responsibility. Figures on the "cost to the economy" of everything from traffic jams to hangovers are notoriously imprecise, but we know that a significant - and growing - proportion of National Health Service spending is accounted for by conditions for which weight is a contributory or exacerbating factor. Already, for example, more than a million diabetics, about half the total, suffer from the weight-related form of the condition.

That requires a change in the approach of the Government. Tony Blair's speech last month recognised this, and it marked a shift from his glib attempt to abdicate responsibility two years ago, when he said: "I am responsible for many things, but I can't make people slimmer." Of course, he cannot do so directly, but individual behaviour can be changed through education and judicious use of other levers of the state. Smoking and drink-driving have been suppressed in this way; controlling obesity will be harder, but it can and must be done.

Education is the key, although urban planning to encourage greater walking and cycling is also important. If people understand how exercise and healthy eating are in their own interests, they are more likely to make healthy choices. Ministers, schools, local councils and food retailers are moving in the right direction, but too slowly. A greater sense of urgency is needed.