The Big Question: Can the Government really make us eat less and exercise to become slim?

Why are we asking this now?

A campaign to create a "lifestyle revolution" is being launched by the Government tomorrow. Billed as the biggest ever, it is called Change4life and features a unique collaboration between Government and business to persuade people to eat more healthily and take more exercise. The message will be reinforced with advertising in Tesco, the Co-op and convenience stores nationwide promoting fruit and veg and other healthy products. The London marathon, sponsored by Flora margarine, will be branded with the Change4Life logo, and Kelloggs is to expand its breakfast clubs and launch Swim4Life. Other firms involved include Cadbury, Coca Cola, Kraft, Mars, Nestle and PepsiCo.

Why do we need to revolutionise our lifestyles?

Because our existing way of life is killing us softly – not with bullets, or poisons or viruses or hunger, but with an excess of fat and sugar...and sloth. Two thirds of the population are overweight or obese and, on present trends, that will rise to 90 per cent by 2050. Obesity already causes an estimated 9,000 premature deaths a year and experts fear its relentless rise could mean the current generation will be the first to die sooner than their parents.

Is this not widely understood?

Apparently not. According to the Government's Chief Medical Officer, Sir Liam Donaldson, research shows only 6 per cent of people understand that obesity is a health risk, increasing the likelihood of cancer, heart disease and diabetes and reducing life expectancy by an average of nine years. "Many see fat as a vanity issue, not a health issue," he said.

What is different this time?

The Government is harnessing the spending power of the companies to back its message about a healthy lifestyle. The £8.7m cost of the campaign is being boosted by an estimated £200m-worth of advertising and marketing pledged by companies including Tesco and the Co-op. "The problem with all nutrition campaigns in the past is that they have been dramatically underfunded," said Jack Winkler, professor of nutrition policy at London Metropolitan University. "This time they are using the spending power of the companies – trying to shift their advertising budgets away from less healthy to more healthy products. This is a very significant change,"

Will this campaign change people's habits?

Past experience is not encouraging. It took more than 50 years to ban smoking in public after the lethal effects of tobacco were discovered – and people still smoke. The problem with all past nutrition campaigns is that they have been swamped by the food advertising of the big companies. As a result, campaign after campaign has had zero impact.

What are the drawbacks?

Companies exploit the link with government for their own commercial ends. There is a revealing moment in the video shown at the press launch of the Change4Life campaign, when Baroness Peta Buscombe, chief executive of the Advertising Association, says it is "good for brands and good for business." Critics fear the Government has been hoodwinked into providing some of the biggest food and drink companies in the land with a gold-plated opportunity to cast their brands in a healthy light. By linking with the Change4Life campaign they automatically show themselves to be on the side of the good guys. "I support the Government's move but the risk is that companies will try and glamorise their whole brand rather than just the [healthy] product," says Professor Winkler.

What needs to be done?

Change4Life needs changed rules for business if it is to be effective.

Families learning for the first time about the dangers of fat in their bodies need help to spot it in the foods they buy. That means improved labelling in supermarkets – with calorie and fat content clearly displayed at the point of sale in fast food outlets, before customers make their choices. Without measures such as these, the Government's campaign risks achieving far less than it should.

Why is food labelling a problem?

Front-of-pack labelling is now the rule across Europe, but there is no agreement on what form it should take. The UK Food Standards Agency favours a traffic-light system – with high fat foods labelled in red and healthier options in green – but the food industry wants Guideline Dietary Amounts, which tell consumers how much fat is in the product. The discussion has been going on for years with little progress. Yet there is no single measure that would better help consumers make healthy choices than improved labelling.

What do the companies say?

A spokesman for Business4Life, which represents 30 companies involved in the campaign, said: "The private sector's vast expertise in advertising, marketing and media can be used to complement and amplify Government's objectives and messages, many of which are often shared with industry."

What do food campaigners think?

Tam Fry, spokesman for the National Obesity Forum and the Child Growth Foundation, said: "We fervently hope that Change4Life will succeed where other department campaigns have failed. Our optimism will be tempered until we see whether the food, advertising and fitness industries really do deliver the promised goods.

"We are tempted to think that the former two are donating millions of pounds to Government as a way of heading it off from imposing the regulation it fears."

Is it all bad news?

No. According to Will Cavendish, director of health and well-being at the Department of Health, there has been a massive increase in the advertising of healthy foods over recent years, resulting in big increases in consumption of fruit, vegetables, brown bread and semi-skimmed milk: "Globally we are regarded as one of the most advanced countries in tackling obesity. Childhood obesity, having been rising for years, has flattened out in the last few years and may be beginning to fall. We are beginning to have an impact."

What can individuals do for themselves?

People will be able to call a dedicated helpline and speak to specially-trained advisors for advice on exercise, nutrition and support services. A website has also been set up to bring together more than 45,000 groups and projects aimed at promoting healthy living. Next June and August, the Fitness Industry Association will launch MoreActive4Life, which will give people free access to health clubs and leisure centres for a four-week period. In August, Asda will launch Bike4Life to promote cycling to families.

The Change4Life advice phone number is 0300 1234567.

Will this latest campaign succeed where others have failed?

Yes...

* It is the biggest campaign ever, launched with the involvement of thousands of organisations.

* For the first time it is harnessing the marketing power of big business with its huge budgets.

* It has to succeed, because the alternative of ever-rising obesity is too awful to contemplate.

No...

* It is extremely difficult to change individuals' behaviour, as past experience with smoking shows.

* Food companies may exploit the opportunity of the link with Change4Life to boost their brands.

* Without extra measures, such as improved food labelling, the initiative risks foundering.