United Nations: Infants under the age of one year should not be exposed to electronic screens at all and "sedentary" screen time for children under five must not be more than an hour a day, according to the WHO's new guidelines.
The guidelines were issued as part of a campaign to tackle the global obesity crisis and ensure that young children grow up fit and well, particularly since development in the first five years of life contributes to children's motor and cognitive development and lifelong health.
In recommendations specifically aimed at under-fives for the first time, the UN health agency said that about 40 million children around the globe - around six per cent of the total - are overweight. Of that number, half are in Africa and Asia, it noted.
The World Health Organization (WHO) said that children under five must spend less time sitting watching screens, or restrained in prams and seats, get better quality sleep and have more time for active play if they are to grow up healthy.
"Achieving health for all means doing what is best for health right from the beginning of people's lives," WHO Director-General Tedros Adhanom Ghebreyesus said.
"Early childhood is a period of rapid development and a time when family lifestyle patterns can be adapted to boost health gains," Ghebreyesus said.
The new guidelines on physical activity, sedentary behaviour and sleep for children under 5 years of age were developed by a WHO panel of experts.
They assessed the effects on young children of inadequate sleep, and time spent sitting watching screens or restrained in chairs and prams. They also reviewed evidence around the benefits of increased activity levels.
"Improving physical activity, reducing sedentary time and ensuring quality sleep in young children will improve their physical, mental health and well-being, and help prevent childhood obesity and associated diseases later in life," says Dr Fiona Bull, programme manager for surveillance and population-based prevention of noncommunicable diseases at WHO.
The guidelines which refer to passive activities such as watching cartoons, for example, as opposed to going online to talk to a grandparent - build on data gathered in countries including Canada and Australia, which show that as many as 75 per cent of children do not have healthy lifestyles.
"Sedentary behaviours, whether riding motorised transport rather than walking or cycling, sitting at a desk in school, watching TV or playing inactive screen-based games are increasingly prevalent and associated with poor health outcomes," says WHO's guidelines on physical activity, sedentary behaviour and sleep for children under five.
Noting the emergence of on-screen applications that help users understand how long they are spending on their devices, Bull noted that there was still much uncertainty about their health impacts.
"This is a recent development and I think it is a signal that the digital industry is also wary about the addictive nature the time that's being spent using these in different ways.
"Of course, all of us are using them for work, we're using them in schools for education, we're using them at home for education. It's about managing the use of these valuable tools and about watching both the benefits and the risks," she said.
The guidelines recommended that infants (less than one year) should be physically active several times a day in a variety of ways, particularly through interactive floor-based play. They should not be restrained for more than one hour at a time, whether in prams/strollers, high chairs, or strapped on a caregiver's back.
Screen time for them is not recommended at all. For young children aged two years, sedentary screen time such as watching TV or videos should be no more than 60 minutes and the less is better.
Children 3-4 years of age should spend at least 180 minutes in a variety of types of physical activities at any intensity, of which at least 60 minutes is moderate- to vigorous intensity physical activity, spread throughout the day. Sedentary screen time for this group of children under age 5 should be no more than one hour and less is better.
The WHO said that failure to meet current physical activity recommendations is responsible for more than 5 million deaths globally each year across all age groups.
Currently, over 23 per cent of adults and 80 per cent of adolescents are not sufficiently physically active. If healthy physical activity, sedentary behaviour and sleep habits are established early in life, this helps shape habits through childhood, adolescence and into adulthood, the agency said.
"What we really need to do is bring back play for children. This is about making the shift from sedentary time to playtime, while protecting sleep," says Juana Willumsen, WHO focal point for childhood obesity and physical activity.
The pattern of overall 24-hour activity is key: replacing prolonged restrained or sedentary screen time with more active play, while making sure young children get enough good-quality sleep.
Quality sedentary time spent in interactive non-screen-based activities with a caregiver such as reading, storytelling, singing and puzzles is very important for child development.
Further, the important interactions between physical activity, sedentary behaviour and adequate sleep time, and their impact on physical and mental health and wellbeing, were recognised by the Commission on Ending Childhood Obesity, which called for clear guidance on physical activity, sedentary behaviour and sleep in young children.
"More is better," the WHO report maintains, suggesting that carers should engage in interactive floor-based play and ensure that babies who are not yet walking spend at least 30 minutes on their stomach, rather than sitting in a chair.
"The advice is where possible, to move from sedentary, passive screen time to more physical activity while at the same time protecting that very important quality sleep.
"And what's particularly important is that quality interactive play with a caregiver that's so important for early childhood development that sedentary time should also be protected," Willumsen added.