They topped the Christmas ratings with Wallace and Gromit's bakery adventure, A Matter of Loaf and Death, but Aardman Animations' latest challenge is their most daunting yet.

A cartoon advert by the award-winning firm will be the centrepiece of a £75m government marketing campaign intended to make the public aware of the fatal link between expanding waistlines and life-shortening disease.

The ambitious Change4Life strategy will also feature a rebranding of the London marathon and will embrace supermarkets and food producers such as Pepsico as well as voluntary groups and fitness clubs in an attempt to curb what ministers regard as a national crisis.

The campaign is aimed at reducing the 9,000 premature deaths a year attributed to obesity. The government claims it will work because it believes public information campaigns were central to people stopping smoking. The crisis will cost £50bn by 2050 - half the annual NHS budget - if the current trend continues.

The TV adverts, the first of which goes out tomorrow, will tell the story of primitive man's descent into flab, depicting colourful characters swinging clubs and climbing fruit trees in the Stone Age before they succumb to a more sedentary modern lifestyle.

They highlight the dangers of fat in children's bodies in graphic form, linking fat to disease and early death, and urge parents to make their sons and daughters more active. As part of the campaign, the London Marathon's sponsor, Unilever, will promote Change4Life alongside the Flora margarine logo.

The public health minister, Dawn Primarolo, said: "This is a long-running and concerted effort to change behaviour and it is not going to happen overnight."

The government says there is an urgent need to reach many families who do not realise that their lifestyle and diet are putting their children's health at risk.

"The research we undertook for this campaign showed that only 6% of people understood the links between obesity, overweight and adverse health effects," said chief medical officer, Sir Liam Donaldson. "Yet we know that without any intervention, 90% of children will be overweight by 2050 and at risk from coronary heart disease and diabetes."

The latest data from the national measuring scheme has shown that one in four children are overweight when they arrive at primary school and one in three by the time they leave. Obesity reduces life expectancy by nine years. People who are severely obese may die 11 years earlier than their counterparts.

Yet the campaign, which will cost £8.7m in the first three months and £75m over three years, has taken a long time to come to fruition. Critics have accused the government of taking its time in deciding its response to the fast-growing epidemic. It commissioned the Foresight report into the causes of the problem and possible ways forward, but that was published in October 2007 - and at the same time the government postponed its target date for halving childhood obesity from 2010 to 2020.

Social marketing - using all the persuasive weapons in the armoury from advertising to promotions on healthy food in supermarkets and incentives to get involved in exercise - will work, health officials say, because it succeeded in making people realise the health dangers of smoking cigarettes. "With obesity we are probably back in the 1950s as far as public understanding is concerned," said Donaldson. "Many people see fat as a vanity issue, not a health issue."

The involvement of food corporations, like Pepsico and Kelloggs, and supermarkets, criticised in many quarters as part of the problem, is controversial. But Donaldson said it would act as a restraint on the development and marketing of less healthy foods. "I think if a company like Pepsico and some others get involved in this, they are going to be subject to intense scrutiny by committing to a healthy cause. It is a very good way of keeping them under pressure to make their products healthier," he said.

Obesity policy consultant Neville Rigby said the willingness of companies to become involved was laudable "if they also agree to make significant changes in the ways they market foods and the kinds of food they make".