Unhealthy modern lifestyles are leading to more and more people becoming overweight.

The BBC is launching a campaign to counter this trend. Called Fighting Fat, Fighting Fit, the campaign will use television, radio and the Internet to get its central message across - that lifestyle, not dieting, is the best way to stay trim.

Television and radio presenters such as Dale Winton and Dr Mark Porter will front the campaign, supported by writers and health specialists.

The programmes and features will run for several weeks, and start on Tuesday with Weight of the Nation, to be broadcast on BBC One at 8pm.

It looks at lifestyles in different sections of society and offers advice on the best ways to stay in shape.

Practical advice

Dr Ian Banks, a GP in Northern Ireland, takes part in the show, which is hosted by Dale Winton.

Dale Winton presents the show

He said it was an entertaining programme because it presented people with experience of weight gain offering practical advice instead of skinny people preaching.

Dr Banks said: "We are giving good advice, not patronising advice. I'm overweight myself, so it was given by people with a realistic view of the problem.

"It has the ring of reality about it - that you can do something about being overweight."

And the show's host is no stranger to excess weight - Dale recently lost three stones after adopting a healthier lifestyle.

He said: "I've been a yo-yo dieter all my life and now I have realised that dieting makes you fat. Healthy eating and exercise is my regime for life."

Strange as Dale's realisation may sound, there is a good reason for dieting leading to weight gain.

Forget diets

Dr Banks said: "We tend to think of diets as having a beginning and an end - we eat like mad before a diet and then all we do is think of the things we're going to eat when we finish.

More and more people are overweight

"What happens when you do that is that the body goes into siege mode - it goes into a more efficient mode of storing fat.

"So when excess calories do come along the body stores them as fat, and people get fatter. When people go on a diet they get fatter."

Instead of short-term diets, people should think in terms of a lifetime - "a lifetime of exercise, a lifetime of fruit and vegetables", Dr Banks said.

Eating plenty of fruit and vegetables had been shown to help cut the risk of cancer and heart disease, he said.

He added that in the case of exercise, a little could go a long way. Ten to 20 minutes a day of exercise that leaves you out of breath is enough to remain healthy, he said.

"Just losing the batteries from the remote control for your television set is equivalent to losing two pounds a year in terms of the extra exercise you do changing channels," he said.

Overweight children

However, the nation is getting heavier, and the most telling statistics apply to children.

Dr Banks said that one in three children is clinically overweight, but more alarming is that one in five is clinically obese.

He said the reason for this was the drop in levels in physical activity.

"Children are spending far more time on computer games, which only exercise the fingers and, so I'm told, the brain.

"One of the declines we've noticed is in walking or cycling to school."

He said this was down to parents being afraid to let their children onto the street in case they were hit by a car.

"Part of what we need to address is finding safe ways for children to get to school under their own steam."

He said habits learnt early on could last a lifetime, and have a huge impact.

"Small changes have a big effect on the quality of your health," he said.