by JAMES CHAPMAN and TIM UTTON, Daily Mail

Parents could soon begin to outlive their children because of an epidemic of obesity afflicting the younger generation.

Many youngsters are now so grossly overweight they face premature death caused by a heart attack or stroke.

The impending health disaster is blamed on the rise of aggressively-marketed, fat-laden fast food and couch potato lifestyles.

Professor Andrew Prentice, a leading nutritionist, warned yesterday: 'We have figured out ways of farming our fields without having to put in human labour, the same in factories where everything is done for us by robots. In the home, we have gadgets to do almost everything.

'Link all that up with the seduction of TV viewing and Internet use and you have an explosive package.

'It's going to have massive consequences on our health and a massive effect on our health budget.

'Will parents outlive their children? Yes, when the offspring become grossly obese.' One in ten children starting primary school in Britain is now regarded as alarmingly overweight, increasing to 15 per cent of school leavers.

Professor Prentice told the British Association for the Advancement of Science's annual meeting at Leicester University that he estimated being clinically obese knocked nine years off lifespan.

He added: 'Adolescents are becoming massively obese at a very young age.

'Angina and heart attacks are going to be occurring in these children in the future.'

He said it was alarming that cases of type two diabetes, once described as adult onset diabetes, were now being reported by paediatric clinics.

'Almost all type two diabetes is directly related to overweight, and diabetes is a very serious, life-threatening disease,' he added.

'The younger you are when you become obese, the worse are the serious long-lasting ill effects associated with it.

'If we put these pieces together, these young people are storing up enormous ill health for the future.'

Professor Prentice, who works at the London School of Hygiene and Tropical Medicine, said Britain was now 'not far behind the U.S.' in levels of obesity.

The condition is calculated by dividing a person's weight in kilos by their height in metres multiplied by itself to achieve a body mass index (BMI). A BMI of more than 25 in adults is classed as overweight and more than 30 is obese.

Overall, one in five Britons is obese, a proportion triple that of 20 years ago.

According to the National Audit Office, Britain's burgeoning weight problem costs the NHS £500million in consultations, drugs and other therapies. Obesity causes 30,000 deaths a year.

Type two diabetes is almost exclusively triggered by overweight. Obese women were 100 times more likely to develop it than those of normal weight, and the risk was increased 45 times for obese men, Professor Prentice told the conference.

Complications include heart disease, stroke, kidney failure and blindness.

He said fast-food diets and sedentary lifestyles were to blame. 'It's 50:50,' he added. 'Fast foods are likely to be implicated because they contain a lot of fat.

'The response to the abundance of high-energy, aggressively marketed foods and the sedentariness induced by TV is a pandemic of obesity.' Even if a miracle drug was discovered to treat the problem, the costs of treating the 60 per cent of the population who are overweight would be unimaginably huge.

The only hope was action by Government and business across a vast range of areas.

'We have got to have action in every walk of life, from transport policy to food policy to safety policy, so that kids can walk to school and play outside safely,' he said.

'In education policy, we need to get exercise back into the curriculum.'

One in four children watches four hours of TV a day and only a third of schools offer two hours a week of physical activity.

The professor said: 'We are in an absolutely fascinating moment of human evolution.

'It's parallel with the increase in height two centuries ago as we pulled out of the desperate diet of the Middle Ages.

'Now we are going outwards in terms of girth, rather than increasing height. The important difference is that while the increase in height was beneficial, the reverse is true for obesity.'

David Barker, of the British Heart Foundation, said: 'Young people can actually help keep a healthy heart and control obesity by eating a diet low in saturated fat, eating five portions of fruit and vegetables a day, and making sure they get physical activity for 30 minutes a day, five times a week.'