Following a worrying survey into the couch potato lifestyle of Britain's teenagers, Siobhan Ryan looks at the problem of obesity among many young people.

When he was 12, Josh Cater spent most of his time sitting slumped in front of the television, eating junk food and rarely taking exercise.

As the weight piled on, he became lethargic and found it difficult to make friends. He seldom went out after school, meaning the vicious circle continued.

One day Josh realised his behaviour could affect his health for life unless he changed.

Two years later, he has shed two stone, exercises regularly, watches what he eats and has a wide circle of friends.

Josh, from High Street, Ardingly, said he had no interest in going out and taking part in sport two years ago.

He said: "We didn't go out as a family and do things and I just let myself go. I suppose if I had been forced I might have gone but it is difficult to get someone to do something if they don't want to.

"My mother is quite active and often does things like walking but I just wasn't interested in anything like that.

"I wasn't any good at sport. I had got into a rut."

For Josh's mum Claire, seeing the teenager grow increasingly isolated and depressed was difficult.

She said: "When his older brother Alex was a toddler, I was just starting out in my career and had time to take him out and get him interested in activities.

"But when Josh was young my career was at its height and I was working long hours.

"I was often too tired to spend the time with him he needed and this, along with the fact we had moved to the South and were no longer near other family members, meant that support network was lost as well.

"I wasn't able to instil in him the pattern of behaviour he needed.

"It's vital that children are encouraged to be active and take part in exercise when they are very young so it becomes a habit.

"But it's never too late to start, as Josh has proved. It takes a lot of courage to get out and completely change your lifestyle.

"He is a completely different person."

Josh said changing his lifestyle had not been easy but he was determined.

He said: "At first, the family didn't think I was serious. My mum bought me a bike to encourage me to get out and about.

"I started doing gentle exercise at first but even that tired me out. After a while, I started to get fitter and things became easier."

Josh has been instrumental in setting up a web site developed by healthcare organisation Bupa aimed at encouraging people to get active.

He said: "We try to get the support of boy bands and other groups and use slang instead of formal words.

"It has been a success and we have had a lot of feedback from people saying how useful it is."

The web site can be accessed at www.getoffthecouch.co.uk A recent Mori study commissioned by Bupa found, of 1,000 teenagers surveyed, only 13 per cent spent most of their spare time playing with other youngsters.

More than half of them, 61 per cent, thought they did not spend enough time being active with their family.

Most blamed their parents for their family's inactivity with one in three citing their parents' lack of time as the reason.

One million people under 16 in the United Kingdom are now classed as obese, which is the biggest cause of ill health and visits to the doctor.

It causes 30,000 premature deaths and costs the economy more than £2 billion every year.

Young couch potatoes are 30 per cent more at risk of serious, and often fatal, illnesses like heart disease and diabetes in later life than active counterparts.

Inactivity can also have a negative impact on school performance resulting in lower grades.

Dr Paula Franklin, assistant medical director at Bupa, said: "Today's couch potatoes are likely to be tomorrow's sick adults.

"Unfortunately, most bad habits are formed in childhood and are therefore very hard to break."