The UK is in the grip of an obesity epidemic and young people are increasingly the victims. Over the past 20 years obesity levels have nearly tripled and today 9 per cent of pre-school children and 17 per cent of 15 year olds are clinically obese. Children are growing up in a society where half of women and two-thirds of men are overweight or obese.

The cause of overweight and obesity is simple: an imbalance between the number of calories consumed compared with calories expended. How to tackle the problem is far from simple and one that has no ready answers.

There is no shortage of villains in this piece - dwindling activity levels, the relentless advertising of high-fat, high-sugar processed food to children, and the wall-to-wall availability of fast food are all said to contribute to the problem.

The paradox is that as young people are becoming fatter, the pressure on them to conform to unrealistic ultra-thin body shapes has never been greater with one survey finding that 90 per cent of 11 to 14-year-old girls were unhappy with their body shape.

"Obesity is often referred to as a time-bomb - well I have to tell you that it has gone off," says Ian Campbell, chairperson of the National Obesity Forum. "We are seeing type two diabetes in obese children, and two-thirds of obese adolescents have high blood pressure, increased cholesterol and impaired sugar tolerance which are increased risk markers for heart disease and diabetes," he says.

Campbell blames the "food revolution" of the past 20 years. "Calories have become cheap and high in fat and sugar," he says. However, he acknowledges that alternatives are difficult for many disadvantaged families. "If you live in a 'food desert' area where public transport is poor and you can't afford a car then your shopping options are very limited," he says.

Young people's increasing inactivity is equally worrying. "Kids spend upwards of 16 hours per week indoors and this must change," Campbell says. Parents worrying about "stranger-danger" and traffic keep young people at home, but other factors play a part. "One of the most common reasons young people cite for not playing outside is complaints from neighbours," Campbell says.

Emotional health
While obese youngsters' health problems are well documented, the implications for their emotional health are equally severe, and they have a tough time with bullying, low self-esteem, isolation, and depression.

Jenny Walker is team leader of one of the few projects in the country that is helping obese young people. The Watch It scheme in Leeds is a pilot project running clinics for seriously overweight children and teenagers in disadvantaged areas in the south and west of the city, run by a multidisciplinary team of paediatricians, dietitians, child and adolescent mental health workers, and community workers.

The project uses the Healthy Education Lifestyle Programme developed by Dr Deborah Christie, a clinical psychologist at University College London, and gives advice on healthy eating, exercise and how to change habits. The clinics run from 3pm to 6pm so young people can drop in on their way home from school.

"We try to get parents or carers to buy into the service too," Walker says. "It's important for them to understand what we are trying to do and to help the young person change their eating patterns and behaviour."

The emphasis is on stabilising their weight and helping them to feel better about themselves. "We don't deal in diet sheets," says Walker. "Most of these children are desperately unhappy - they are bullied, socially excluded with virtually no self-esteem. Until you start to work with them on these issues you can't move on to tackling the physical side of the problem."

Some of the clinics are run from leisure centres and there is a strong emphasis on physical activity. Walker says: "It's crucial that we help them increase their activity levels. Most do no exercise whatsoever and are exempt from games because they find it so difficult. We don't expect children to lose weight - we hope they will stop gaining it. The biggest thing is that they just feel better about themselves and are more confident."

Watch It has had encouraging results, and there has been an overall modest decline in the young people's weight. But there are very few projects like this.

Deborah Christie, who created the Help programme, says nobody holds a magic wand when it comes to treating obesity. "Diets don't work - they introduce restraint and restraint causes a diet/binge eating cycle that makes kids very unhappy. I think this is more unhealthy than being overweight," she says. "It's very na‹ve of us to think that we can come up with a simple model that will eradicate the problem."

Early intervention

What does work, she says, is the model Watch It uses, and it is this sort of service she would like to see rolled out across the UK. Crucially, she says, we must invest in early intervention. "If I see a child with an increased body mass index at the age of nine, there is a real chance to help them change their eating behaviour. By the time they are teenagers this is much more difficult."

The government's response has, to date, been fragmented. There are initiatives such as the Healthy Schools Initiative and the Department for Education and Skills' Food in Schools pilot project, but nationally, there is a lack of services to help obese young people and their families.

The NOF's Campbell is frustrated by the lack of action. "My concern is that the problem is too serious to wait for the results of these pilots. Speed is of the essence - we must tackle the problem now." He also urges the government to "kick the food advertisers into touch". He says: "The government will tell you that the food advertisers do have some restrictions on them but in reality they have a free rein."

However, there are signs of action on the horizon. On 3 February the health secretary John Reid announced that a white paper on public health would be published in the summer to address the issue and that consultation will begin next month.

Many hope the government will be brave and invest in a joined-up strategy engaging professionals, parents and young people and focusing on early intervention. If not, we face the real prospect that this generation of young people will not live as long as their parents.

A useful exercise   

It's Friday night and 12 enthusiastic young people from a mixture of ethnic groups are being put through their paces at Whitechapel sports centre. 

They are here for the second of two weekly sessions that give them the opportunity to play sports, use the gym and improve their fitness. It may not seem remarkable, but these young people are all seriously overweight and, if it were not for the Whitechapel Club, a six-month pilot project run by Tower Hamlets Council, they would be unlikely to be doing any exercise at all. Here, they get involved in basketball, football, hockey, trampolining and gym sessions under the supervision of fitness staff. They have all been referred by dieticians at the neighbouring Royal London Hospital and, watching them play basketball, it's hard to believe they have health problems. "All of them are carrying one or two risk indicators for diabetes or coronary disease," says Susan O'Callaghan, who runs the club and is physical activity development officer at the sports centre.  

"One has full-blown adult diabetes, two have sleep apnoea, others have high blood pressure and asthma." Confidence is also an issue. "Many have been bullied at school. One boy gets a taxi to and from school because he is scared to be out alone," O'Callaghan says. 

Three months in, O'Callaghan has seen a great improvement in fitness levels."I can see the change in them. They have more energy, their clothes are looser and their peak flow rates have improved," she says. Tests will soon establish how much fitter participants are. 

Susan Wright's daughter Stephanie is 14 and joined the scheme reluctantly. "She associated gyms and exercise with fit, thin people. When she saw everyone had weight problem she felt comfortable." 

Lynn Porter's daughter Terri is 13, and she too has enjoyed coming. "She's more active now," Lynn says. Terri likes the club because she can exercise away from school. She says: "I don't like PE at school because I have to do it with people who are really skinny and I feel intimidated." 

Sixteen-year-old Sara-Jane Perryman says: "I'm definitely going to carry on exercising when this finishes." Her major problem is the attitude of other people, and she wrote a poem (overleaf)to express her feelings. More funding will be needed if the project is to survive and O'Callaghan says there must be more investment in treating children who are already obese. "It's important to focus on prevention, but for many children it's too late - they are already very overweight. But they still have a right to a life, and a right to a good life."

Cruel words   

What children told ChildLine about how being overweight made them feel.    

Becca, 12: "Boys in my class call me names like fat cow, fatty and pudding - they punch and kick me too. I'm scared to go to school, but it's not fair that I have to stay away and get into trouble because of the bullies."    

Sarah, 11: "After someone found out I'd been to the doctor about my weight they started picking on me. They call me  earthquake and whale. I used to play sports but now I don't because people laugh at me."    

Michael, 14: "I get called fat boy at school and I get angry and take it out on my friends."

Six heavy facts   

1 About half a million children in the UK weigh more than 20 per cent above their ideal weight. 

2 National Audit Office estimates that obesity costs the economy £2.8bn each year. 

3 Only 13 per cent of girls and 14 per cent of boys eat the recommended five portions of fruit and vegetables a day. 

4 One in five children eat no fruit or   vegetables. 

5 Only one-third of children receive the government recommended two hours of exercise at school a week. 

6 The number of children travelling  to school by car has doubled in the past 20 years.