This week the Government will deliver its big verdict on the nation's health, warning that we must all get fit to live longer and save the NHS. Here a very typical family is compared to the official ideal. And below Andy McSmith reveals what the doctor will order

Don't smoke, don't get too stressed, don't engage in risky sex without a condom, take exercise, watch your weight, improve your diet, and don't pile sugar on your corn flakes or salt on your porridge.

That is the advice John Reid, Secretary of State for Health, will be giving the nation this week in one of the most important interventions a government has made in the health of the people for many years. It will be contained in a White Paper about as long as the average novel.

Put simply, the rationale behind it is that the NHS is costing the Government a fortune, and it would cheaper if people spent less time slouching in chairs stuffing their faces with chips, chocolate and lager and more time keeping fit.

It is estimated that 63 per cent of British women and 70 per cent of British men are overweight, because of a combination of richer foods and an increase in office jobs that do not require employees to leave their desks.

Obesity is blamed for 30,000 deaths a year in the UK from conditions such as heart disease, strokes and diabetes, and could add £9bn to NHS bills by the end of the decade.

But while Mr Reid, one of the architects of New Labour, wants you to enjoy good health, he does not want you to think that he is introducing a nanny state that will deny people freedom of choice.

In an interview with The Independent on Sunday yesterday he said that the philosophy behind the White Paper is that adults must be given the information to allow them to make an informed choice - but after that, it is up to them if they want to keep up unhealthy habits, provided they do not harm anyone else.

Children's health isanother matter, he added - hence the threat to legislate if TV companies fail to agree to cut the number of junk food adverts seen by young viewers.

One in five girls between the ages of two and 15 is overweight, including 7.8 per cent who are classed as obese. The problem is particularly severe among 10-year-olds, a third of whom are overweight. Sixteen per cent of boys are overweight, and 5.7 per cent obese.

Cigarettes, alcohol and unsafe sex are the other big causes of avoidable ill health. Years of health warnings on cigarette packets have not stopped 13 million Britons, about 22 per cent of the population, from smoking, which is reckoned to cause 120,000 premature deaths a year.

Drinking costs Britain an estimated £20bn a year in lost work days, extra health care, and police expenses - £500m a year is spent by the NHS looking after those suffering the effects of too much alcohol.

Sexually transmitted disease is on the increase. Cases of chlamydia rose by 9 per cent from 82,558 in 2002 to 89,818 in 2003. Since 1996, syphilis has increased by 28 per cent while HIV diagnoses have more than doubled. Altogether in 2003, 708,083 people were diagnosed as having a sexually transmitted disease. There are also 1.8 million people in the UK with diabetes, an increase of 400,000, or 28 per cent, in the past eight years. Obesity and inactivity are said to be the main causes.

"We want people to have responsible sexual relations, drinking moderately, not smoking, sufficiently exercised. The White Paper is about whose responsibility it is," Mr Reid said. "There has to be a balance between rights and responsibilities. Although generally speaking you would achieve that balance by informed choice, certain groups of people are not in a position to make informed choices and therefore a government may have to protect them."

Mr Reid should stop worrying about accusations of "nannyism" and speed up the march towards better health, says the King's Fund, one of Britain's foremost health charities. The apparently benign mantra of giving adults a free choice is likely to discriminate against the poor and the socially disadvantaged, it says.

"It can be more difficult - due to factors beyond their control - for people in poor and socially excluded groups to give up smoking, take adequate exercise or eat healthy food," according to a briefing paper released by the charity yesterday. "Simply encouraging individuals to 'choose' healthy lifestyles will widen health inequalities.

"We are concerned that the Government will fail to act decisively on some issues, because of fears of being accused of 'nanny statism'."

Britain's most typical family: The Wants of Caerphilly, South Wales

John and Claire Want are both 30. He is 6ft tall and weighs 10st 5lb. She is 5ft 8in and weighs 7st 12lb. Children Niclas and Ieuan are five and three. They look slim, but earlier this year their diets and lifestyles helped them to win a contest to find the UK's 'most average' family

Diet The Wants should be fatter, according to the Government. They stray far from the official advice on food, but are still officially underweight. John eats four or five biscuits with each cup of tea (made with sugar and full cream milk). His breakfast is a banana but Claire has sugar on her corn flakes. For lunch they eat sandwiches. John has a mini pie and a packet of crisps with his. A typical dinner is pork chops, mash (made with butter and milk), broccoli and gravy, with sugar-free pop. "I know we should cut down on salt but we never do," says John. They have a take-away once a fortnight. Pudding is yoghurt or crème caramel. Once the children are in bed the couple get out the crisps or chocolate.

Drink Often they share half a bottle of wine over dinner. Once a month John goes on a "crazy pub visit" involving eight pints of beer, sometimes with spirit chasers. Claire has a pint of cider three or four times a week. They drink two or three pints of water a day. Exercise John plays football most weeks. "I try to walk but end up driving." Claire walks the kids to school.

Habits John sleeps seven hours a night, Claire six. Like most of us they don't smoke. Teeth are brushed twice a day.

Children Niclas and Ieuan eat cereal in the morning, sandwiches for lunch, and the same dinner as their parents. They rarely eat chips. Their two hours of TV a day is the national average. They walk to school or playgroup, and Niclas has PE twice a week. They sleep for 12 hours.

Britain's most healthy family: The Perfects of Happy Valley, Pleasantshire

Peter and Angelica Perfect are both 30. They are as tall as John and Claire Want but have the ideal weights for their sizes, 11st 5lb and 9st 13lb. The children, Anthony and Cherie, are five and three. The Government wishes we were all like the Perfects. Naturally, they don't exist

Diet Peter and Angelica Perfect follow every scrap of government advice religiously, so it's fruit for breakfast with high-fibre cereal. Dairy products are eaten "sparingly", as the Department of Health suggests. They eat red meat in moderation, with the fat trimmed off. Lunch is lean chicken with steamed vegetables (two of five daily fruit and veg portions). Dessert, if there is one, is low-fat yoghurt. The Perfects know they are allowed a bag of crisps a day, but do not want to burden the health service by joining the 70 per cent of men and 53 per cent of women who are overweight.

Drink Peter Perfect never drinks more than the recommended four glasses of wine a day or two pints of beer. Angelica has three glasses of wine at most. After two or three litres of water a day, they empty their bladders often.

Exercise The sight of them jogging off to play tennis or golf leaves neighbours feeling tired and overweight, but the Perfects know they should exercise moderately for at least half an hour a day. It's what the Chief Medical Officer would want. Angelica reminds Peter that mowing the lawn or vacuuming the carpets count as exercise too.

Habits Smoking? You're joking. They support an outright ban. They brush and floss before at least eight hours' sleep.

Children After one hour of (educational) TV, Anthony and Cherie are marched outside for an hour of physical play. They snack on nuts, grapes and carrots before sleeping for 11 hours. And they dream about going to McDonald's.