Is your TV killing you? Every hour of viewing takes 22 minutes off your life, couch potatoes are warned

• Six hours TV a day can cut life expectancy by five years

Every hour spent watching TV, DVDs and videos as an adult reduces life expectancy by almost 22 minutes, a study suggests.

And viewing TV for an average of six hours a day can cut short your life by five years.

The research claims that a sedentary lifestyle is as bad for health as smoking and obesity, because of the dangers posed by inactivity and the greater opportunities it offers for unhealthy eating.

The academics conducting the study set out to calculate the overall risk to life expectancy from watching television. Their research involved more than 11,000 people over the age of 25.

Writing in the British Journal of Sports Medicine, they concluded: ‘TV viewing time may be associated with a loss of life that is comparable to other major chronic disease risk factors such as physical inactivity and obesity.’

This finding is also comparable to risk factors such as smoking, with other research showing that one cigarette cuts 11 minutes off a lifespan – equivalent to half an hour of watching TV.

The researchers, from the University of Queensland, used information from the Australian Diabetes, Obesity and Lifestyle Study, together with population and death rate data.

But they said: ‘While we used Australian data, the effects in other industrialised and developing countries are likely to be comparable, given the typically large amounts of time spent watching TV and similarities in disease patterns.’ In the UK, the average amount of time spent watching TV is four hours a day compared with five hours in the United States.

Researchers from the Harvard School of Public Health, Boston, said it was ‘biologically plausible’ that prolonged TV viewing results in disease and premature death. Other work suggests that sedentary behaviour is linked to obesity, high levels of bad blood fats and other heart disease risk factors, and more opportunities for grazing on junk foods.

Earlier this year, a separate study suggested the risk of developing type 2 diabetes and heart disease, or dying prematurely, rises by as much as 20 per cent after just two hours a day in front of the box.

England’s Chief Medical Officer, Sally Davies, said: ‘Physical activity offers huge benefits and these studies back what we already know – that a sedentary lifestyle carries additional risks. We hope these studies will help more people realise that there are many ways to get exercise.’

Another study shows that exercising for just 15 minutes a day can increase your lifespan by up to three years.

It can reduce the risk of early death by 14 per cent, with each extra 15 minutes reducing all-cause death rates by 4 per cent.

Exercise also protects against cancer, although the benefits peak at 100 minutes a day, says the study in The Lancet medical journal.

It involved more than 400,000 adults taking part in a medical screening programme in Taiwan, whose progress was followed between 1996 and 2008.

The experts found that if individuals engaged in low-volume daily exercise, one in six all-cause deaths could be postponed.