Martin Macari’s story of life in the slow lane is not unusual at the summer camp he’s just completed. “I used to get bullied at school. PE was especially difficult. You had to run cross-country, and if you came in last the teacher would make you run the course again. I’d always be in the last five. So I just used to bunk off to avoid it.”

With time, the bunking off became more frequent and Martin, now 17, stopped going to school altogether before he’d taken his GCSEs. “I just couldn’t face going into school. I hated it,” he says.

But there’s a positive ending to his story - he’s now at college, making up for lost time, taking academic and vocational courses. And over the summer holidays Martin has learned some rather different lessons that with any luck will prove just as valuable. He’s just spent six weeks at Carnegie National Weight Loss Camp for Children, the first camp of its kind, which is running for a second year in the UK. Based at an independent boarding school, Woodhouse Grove near Leeds, it is adapted from models of the much-criticised American “fat camps”, where overweight children are put on restricted diets and made to follow a gruelling regime of physical activities.

But Carnegie insists it is different. Rather than depriving children of the food they need, the team from Leeds Metropolitan University, which runs the camp, provides food children like to eat, and offers them a chance to lose weight by learning how to enjoy being active.

So, along with three meals a day plus puddings - hamburgers, pizzas, chips, salads, ice cream, cake, jelly - they acquire skills they’ve never learned at school, such as the mechanics of basketball, football and badminton. And once they find they enjoy these, as well as dancing, camping, walking and swimming, they’ll continue, the thinking goes, to take part in activities at home and to stick to three square meals a day with nothing in between.

Childhood obesity is a growing problem in Britain and is already at acute levels in the US, where one in 10 children is obese and one in five overweight. Last month, authorities in Albuquerque took a child aged three into care because her weight - 8st 7lb - was said to be life threatening.

Dr Susan Jubb, head of nutrition and health at the Medical Research Council, says British school children are spending less time in PE lessons than any in Europe, and that this “squeeze” on the timetable is worsening as a result of the Government’s emphasis on academic results. “If we want our children to be healthy and well adjusted they need to be offered activity habits for life and not just competitive sports,” she says. “Even sporty children find team games difficult to pursue when they’ve left school.”

She cites the case of the Netherlands, which has half our rate of obesity and where most children cycle to school. Cycling, swimming, aerobics and badminton should be given a higher priority in British schools, she says.

For the chosen few in Leeds, learning how to be active comes at a price. Although Carnegie is a non profit-making operation, it charges pound;1,950 per child for the six-week programme, to cover the costs of accommodation and staffing. Most children are funded by their families, while a few have grants from health and social services.

Each child goes through a careful medical assessment upon arrival. Partly funded by the National Heart Research Fund, the Carnegie camp will admit only young people who are clinically obese. World Health Organisation guidelines are followed to assess appropriate calorie intake, with allowance made for individual energy needs and metabolic rate.

Each week the children are monitored, including checks on body fat levels rather than weight, which is affected by growth and muscle development.

Camp director Paul Gately, LMU’s senior lecturer in sports science, is passionate in his belief that this is the right way to help children lose weight. “Over the past six years I’ve researched the US camps, and I’ve seen the terrible mistakes they’ve made and the inappropriate way they’ve looked at the issues,” he says. “Although it’s biologically true that if you eat less and exercise more you’ll lose weight, it’s unrealistic - particularly for kids. Children need more food than adults because they’re growing. And if you give them too little, they’ll just go away and binge.”

That explains the high failure rate of the American camps, Mr Gately says, where “year after year, the same kids come back bigger and bigger each time”.

Because short-term weight loss has been shown to yield only short-term results, he and his team of researchers, teachers and dieticians decided to emphasise physical activity rather than diet. They were determined that activities should be built on enjoyment and success, rather than agony and failure - the feelings commonly engendered by school sport in many overweight children.

The Carnegie camp claims physical and psychological success for its participants: on average, children increase their fitness levels by 20 per cent and lose between 1 and 1.5 kilos a week. The children report that they are less worried about their weight, figure and looks than when they first came.

With one staff member for every four children, the 70 campers - aged 11 to 17 - are given the attention and encouragement they rarely, if ever, receive at school.

“PE teachers like kids who are good at sport. Those who are overweight are simply not provided for,” says Paul Gately. “Even the best PE teacher can’t differentiate teaching for a group with wide abilities, so those who are struggling always lose out and feel failures.”

The Leeds team believes problems start at primary school, where the dictates of the PE syllabus hinder the development of core sports skills. So children, particularly those who are overweight, are entering secondary school without being able to throw or kick a ball and believing they are useless at sport. The Carnegie staff have found that while such children often profess to hate sport and physical activities, a change of environment, and making the activities fun and non-competitive, turns their attitudes around.

The young people here certainly seem to be enjoying themselves, happily playing badminton after their swim. Following a regime that would have many slimmer kids sulking by mid-morning, they take part in six activities during the day as well as an evening activity for one-and-a-half or two hours. There’s relaxation time in between and no one, says Paul Gately, is coerced into taking part.

Which is all very well in the six weeks they’re at the camp. But what happens when they go home, surrounded by the siren calls of cream cakes, crisps and marathon sessions in front of the telly?

“A key part of the programme,” he says, “is education. Evidence from the US shows that 90 per cent of the young people who manage to keep their weight off up to three years after attending the camp are engaged in sports activities in and out of school and have parents who are involved in their weight loss programme. An important part of this involvement means not buying snack foods that can tempt their children.”

So, as well as regular talks on nutrition and exercise, and discussion groups on body image for the campers throughout the six weeks, parents are also invited to a session at the beginning to hear the approach of the camp and how they can sustain it. Throughout the rest of the year, families receive fortnightly newsletters to help them keep up the momentum. If there is a sticking point to the whole approach, this is it.

Certainly the campers seem keen to stay active once they get home but are also aware of the demands of school and peer pressures. Natalie Coleman, 16, has returned to the camp for her second year. She lost 10 kilos last year and reckons she’s done about the same this year. “When I got home last time, keeping up the food diet wasn’t as hard as maintaining the physical activity. I continued to lose weight for a while then put it back on again then lost some more, so when I came back to camp I was the same as when I’d left last summer.”

How will she manage to be physically active while studying for her A-levels? “I’ve always been into swimming, so I’ll keep that up when I can and I plan to ride my bike or walk to school when the weather’s decent.”

Kyle Jamie Taylor, aged 14, also hopes to carry on the good work. “It’s really about having willpower instead of doing what friends do,” he says. “But it doesn’t mean I have to change my lifestyle that much. If friends sit around eating crisps, I can have low-fat ones, or fruit. And I’ll probably get into after-school sports like football and rugby. Even at home, I can go out and practise basketball shots or go walking instead of sitting around all the time.”

Whether Kyle succeeds remains to be seen. But as far as Paul Gately is concerned, the issue isn’t about continuing to lose a kilo a week but about being physically active every day to keep fit and healthy and to hold on to self-esteem. “Obesity,” he says,” is the last form of discrimination in our society, and obese kids get discriminated against almost more than anyone else. That’s scary.”

To find out more about the Carnegie National Weight Loss Camp for Children, contact Paul Gately at Leeds Metropolitan University on0113 283 2600 ext 3579 or email him at p.gately@lmu.ac.uk

Obesity: the facts

* Childhood obesity is on the increase. One UK child in three is now overweight

* A 1999 study published in the British Medical Journal found more than 20 per cent of four-year-olds were overweight and 7.6 per cent obese * Between 1972 and 1994, English boys grew 10 per cent fatter and girls 5 per cent; in Scotland the respective figures were 13 per cent and 16 per cent

* Some UK schoolchildren get as little as one hour a week’s physical activity in PE, less than any other children in Europe

* Among adults, 17 per cent of British men and 20 per cent of women are classified as obese

* Obesity-related health problems account for 8 per cent - or pound;3.5 billion - of the NHS annual budget. Chief diseases are some cancers, heart disease, diabetes and arthritis