Parents have been advised not to let their children watch TV until the age of three as new research shows kids spend more time watching screens than they do in school.
Researchers at the Royal College of Paediatricians and Child Health found that by the age of 18, the average child will have spent three full years watching screen-based media. This equates to 17.6 years by the time people reach 80.
Published in the Archives of Disease in Childhood, Dr Aric Sigman said the average teenager spends six hours outside of school looking at screens. He wrote: "Reducing total daily screen time for children, and delaying the age at which they start, could provide significant advantages for their health and wellbeing."
Sigman added that there were increasing concerns over how much 3D media children see, as this could affect the child's depth perception development.
He recommended one hour of screen time for 7-12-year-olds, 1.5 hours for 12-15-year-olds and two hours for those over 16.
"While many questions remain regarding the precise nature of the association between screen time and adverse outcomes, the advice from a growing number of both researchers and other medical associations and government health departments elsewhere is becoming unequivocal: reduce screen time," Sigman wrote.
Sue Palmer, child development expert and author of Toxic Childhood, said that while excessive amounts of TV could have adverse effects on children with certain predispositions, the inactive lifestyle it leads to is of more concern.
She told IBTimes UK: "The more small children get hooked on sedentary forms of entertainment, rather than playing and moving about as their bodies are meant to, the more likely this is to become a default habit.
"There is a huge concern that children are simply not active enough, and one of the reasons for this could be that, increasingly, sedentary screen-based activities taking over. They're not doing the things they ought to be doing during the first three years when their brains develop very rapidly."
Recent research by the University of Minnesota found that reducing the amount of TV viewing may be an effective strategy in preventing excess weight gain among adolescents. An association between decreased weight gain and a reduction in TV hours was found over a one-year period.
Prof Amanda Kirby, a child development expert based at the University of Wales, explained that children need real-world experiences and physical activity, and said TV should never replace conversation and play.
She said: "Social interaction is essential. A child viewing a programme needs someone with them to engage and ask them what is interesting or not.
"Children who sit eating and watching TV have been shown to eat more calories - so this is not good for weight gain as well."
Kirby noted that consoles such as Wii and PlayStation where the game involves physical activity could have some benefit. "There is nothing like the real thing though," she said.
Offering parents advice on screen-based entertainment, Palmer said: "Make sure children develop active social habits. Five to six hours of screen time per day means some children are missing out on other life experiences needed to grow up healthy and balanced.
"Because children are going to be living an online life, what parents need to do is gradually introduce them to the internet and make sure they know all the safety procedures so once they become teenagers, hopefully they will be able to use the internet sensibly.
"In order to learn self-discipline and self-control needed in order not to become an online junkie, you need a normal balanced childhood that involves outdoor active play and social activities."
Kirby concluded: "Allowing children to drift into a virtual world for extended hours is not good and should be avoided. Why are they watching? What is it for? Nothing can replace sitting around a table and talking through the day together."