The Chief Medical Officer for England did not mince his words when he published his annual report on the health of the nation last month. We are, he said, dangerously fat. Using language rarely associated with government officials, Sir Liam Donaldson described obesity as a time bomb threatening to cause thousands of unnecessary deaths through heart disease, cancer, arthritis and diabetes over the next 30 years.
"The consequences for the population's health, costs to the NHS and losses to the economy will be disastrous," he concluded. Obesity levels in England have tripled in the last decade, a growth so serious that Britain's population could actually find its average life expectancy declining.
A condition traditionally found in adults - of whom one in four is obese - is now emerging as a serious problem for children. Between 1996 and 2001, the proportion of seriously overweight six- to 15-year-olds rose by a frightening 3.5 per cent. For the first time, adult-onset diabetes, an illness strongly associated with excess weight, is cropping up in teenagers, and doctors have resorted to prescribing powerful weight-loss drugs.
One of the largest health authorities in the country, Lothian, which looks after the city of Edinburgh, has decided to take direct action. In an attempt to combat children's fatally unhealthy lifestyles, the Lothian health board has gone beyond the targets and publicity campaigns favoured in Whitehall, and is paying for primary pupils to do extra games classes at lunchtime and after school. Appropriately enough, the money for the scheme, about £200,000 a year, has been raised through tobacco taxes by the Scottish Executive.
These NHS-backed PE classes continue even in the holidays. There were hundreds of Edinburgh children running around the city's sports halls, playgrounds and parks this month, under the supervision of trained athletes and teachers. At the Leith Academy, for example, a comprehensive near the city's docks, you could see groups of eight- and nine-year-olds taking part in "little athletics" courses, with running, jumping and even javelin lessons. Fortunately, these particular javelins were only two feet long and, although they flew many yards, were not the terrifying metal spikes seen at the Olympics. Instead they were made of stiffened foam in livid blue with fins of contrasting red. They are only one part of a range of specialist indoor equipment, including soft shots for putting, and light fabric barriers for hurdling.
The athletics is part of a new summer scheme, "Play4It", which offers sports including badminton, handball, fencing, judo and beach volleyball. Play4It is hugely popular. But the real business for Edinburgh's Sports Development Office comes during term time, when it runs an extraordinary after-school coaching scheme, "Sporting Chance", for children in primary schools around the city.
Sporting Chance emphasises participation and enthusiasm, which from the outset makes it very different from the sports academy approach popular with soccer clubs - who take the most promising youngsters and attempt to turn them into the international players of the future. In fact, football, which has quite enough backers already, makes no appearance in the programme of Sporting Chance. Instead children are invited to take part in athletics, Kwik Cricket (played with plastic equipment), mini tennis and the "fit club", a combination of aerobics, boxercise and co-ordination techniques. In the summer months there's cycling, too.
These sports have been chosen specially to teach physical skills that can be applied across a range of activities, says Robin Yellowlees, head of Edinburgh City Council's Sports Development Office. Part of the idea is to introduce eight-year-olds to games they might not have played previously. If boys struggle at football, for example, they may well think they are no good at any sport. Time after time, the Sporting Chance coaches have found that children who had been written off actually have both enthusiasm and talent when given different choices.
The schools who take part have been glowing in their praise. "The children think it's fantastic," says Lorna Stewart, head of Craigroyston Primary School - and that is exactly the reaction that the health authority is looking for. Professor Peter Donnelly, director of public health and health policy at Lothian NHS, says: "We're trying to get young children established in the idea that exercise is fun - and the emphasis really is on fun. The thing the guys who run it are really good at is high participation rates. Kids who never thought of themselves as sporty take part, and discover they like it."
There have been complaints about overweight young people since long before the days of Billy Bunter and the Magnet magazine. But the scale of the current problem is quite different. "The growth in the proportion of overweight and obese children is a major concern," says Sir Liam's report, which suggests that 8.5 per cent of six-year-olds and 15 per cent of 15-year-olds are sufficiently overweight to be classified as obese.
"Between 1996 and 2001 the proportion of overweight children (aged six to 15 years) increased by 7 per cent, and obese children by 3.5 per cent," it says. "Particularly worrying are the first signs of children presenting with maturity-onset (or Type 2) diabetes, which in the past has occurred in middle and older age.
"Researchers in the United Kingdom have recently warned that the increase in obesity threatens to reverse gains in longevity made during the last 100 years, and in some cases could result in parents outliving their children."
There is evidence that Scotland - apocryphally home to the deep-fried Mars Bar - is particularly badly hit by a combination of bad diet and lack of exercise. North of the border, 8.6 per cent of three- to four-year-olds are obese, according to the Scottish Executive. The UK average for that age group is 5 per cent.
The reasons for it are depressingly familiar. Children are snacking more, eating bigger portions and exercising less. "Over the past three or four decades, much of the exercise built into everyday life has disappeared," says Professor Donnelly. "Walking to school or playing football in the streets - that stuff's gone for a lot of kids. No one used to have Cartoon Network on the telly. And if you look at the stuff advertised for kids, the overwhelming majority of it is high in sugar, fat and salt. Cartoon Network is not surrounded by images of fresh fruit and exercise."
Figures from his health authority show that one-third of all boys and two-thirds of all girls are failing to get the level of exercise they need to keep healthy. Because children are growing, he says, they need even more exercise than adults, and in primary school they should be aiming for at least an hour a day.
The Sporting Chance scheme is trying to offer more than a bit of extra PE. The health authority and the schools taking part hope for long-term benefits, with children making exercise as much a part of their daily routine as television or high-fat, high-sugar snacks. So the scheme is specifically linked to community sports clubs, which the children are encouraged to sign up for when they reach a certain standard. The coaches who tour the city's schools on behalf of Sporting Chance not only do the "taster" sessions and regular coaching: they also accompany the children to the community clubs for the first session or so, to help them feel a little more comfortable.
"The really important thing they do is manage the transfer into local clubs to get some sustainability," says Professor Donnelly, who believes that early habits are key. "How many people do you know who took up smoking in their thirties?" he asks.
Sporting Chance is very much aware that obesity is a class issue. The children with the least healthy lifestyles are those on the poorest estates. Figures for England show that, overall, in 2001 only 14 per cent of men and women were obese, compared with 28 per cent of women and 19 per cent of men in unskilled manual occupations.
So the project has concentrated largely, although not exclusively, on schools with higher-than-average free school meals figures. The coaching sessions cost nothing to families entitled to free school meals, and only £1 to the rest.
There is also a gender divide. Girls appear to get even less exercise than boys. Research by the Scottish Executive has found that, by the age of 16, two in three girls and one in three boys do not reach the recommended minimum levels of physical activity.
With schools still driven by league table rankings, whether for SATS or GCSEs, there seems to be little prospect of timetabled PE sessions making the necessary difference. According to a recent Ofsted report, around a quarter of current PE lessons are unsatisfactory.
Ministers in London have announced the creation of a Sport and Physical Activity Board in England, run by the Department of Health and the Department of Culture Media and Sport, to try to boost PE and children's links with local clubs. The board may well adopt the sort of direct approach pioneered in Edinburgh. So far, the official response to the exercise crisis has been to set targets, however. By 2006, for example, three-quarters of five-to 16-year-olds in England should be doing a minimum of two hours a week of "high-quality PE". It also says that 70 per cent of the whole population should be doing at least 30 minutes a day of a moderate activity, such as brisk walking, by 2020. This, of course, is nowhere near the life of vigorous activity that growing children require which, in the view of Professor Donnelly, means at least an hour of exercise a day.