Children and young teens should spend no more than two hours playing video games or watching TV a day, according to an Australian study which is sure to strain domestic relations.

Dr Louise Hardy, of the University of Sydney, said her study sought to test the two-hour “small-screen time” guideline issued by the American Academy of Paediatrics in 2001.

While the US guideline was based mostly on expert concerns over how much TV content and advertising a child should be exposed to, Dr Hardy said her study focused instead on fitness.

Children who spent more than two hours a day in front of the television were less likely to be fit, the study concluded, after 2750 New South Wales school children were put through their paces.

“What this study did was to use fitness and see at what point did the small screen recreation impinge on their health,” says Dr Hardy, of the university’s NSW Centre for Overweight and Obesity. “As it turned out, the experts were fairly spot-on – the two hours is a good benchmark.

“Now we can actually say it does directly affect your health rather than this kind of prudence, which says you have been exposed to too much violence and food advertising.”

The school students, aged 11 – 15, were put though a “beep test” exercise which required them to run between two points over decreasing periods of time.

They were also quizzed on time spent playing computer games and watching TV, along with other types of sedentary behaviour, including playing a musical instrument, doing homework or car travel.

Dr Hardy said up to 10 per cent of the sample group reported spending six hours-plus per day engaged in small-screen time – either using a computer, watching television or a video or playing electronic games.

The difference in fitness levels of children who spent more than two hours small-screen time daily was more pronounced in girls than boys, she said.

Despite the findings, Dr Hardy said she expected many children, and parents, would find the time limit hard to accept.

“Computers and TVs and (electronic) games are very much a part of the modern life and a lot of parents find the two hours as almost unacceptable – they scoff at that,” she said.

“But I would argue we scoffed at smoking many years ago, saying it didn’t lead to lung cancer – it has taken a long time for the message to get through.”

Dr Hardy said high levels of sedentary behaviour in children could not only lead to obesity or reduced fitness, but also impact on healthy bone development at a critical time.

The research results are published in the American Journal of Preventive Medicine.