For infants younger than 1, World Health Organization recommends that they be physically active several times a day in a variety of ways, with floor-based play and at least 30 minutes of tummy time. "Not all screen time is created equal".
Some fear that too much screen time reduces the time kids spent connecting and engaging with their caregivers, which is seen as crucial for their social and emotional development.
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.
For the greatest health benefits, how much play time, screen time and sleep should your baby or young child have in a given day?
Even at 1-2 years, though, screen time remains anathema.
Despite acknowledging that its "strong recommendations" were based on "very low quality evidence", the United Nations health agency said its advice could apply to all young children, regardless of gender, cultural background or socio-economic status. "For those aged 2 years, sedentary screen time should be no more than 1 hour; less is better". Long-term consequences can be hard to measure, and ethical concerns prevent experiments in which, for example, one group of infants watches two hours of videos a day while a second group plays outside or chats with parents.
The WHO drew on emerging - but as yet unsettled - science about the risks screens pose to the development of young minds at a time when surveys show children are spending increasing amounts of time watching smartphones and other mobile devices.
When an infant happens to be spending too much time seated, World Health Organization recommends engaging in reading or storytelling with a caregiver - and screen time is not recommended for this age group.
It also recommend children aged two to five years limit screen time to one hour per day of high-quality programming.
The WHO's rules track loosely with those of other public health groups in the United States and elsewhere, which typically have urged limited screen time and copious personal interaction and sleep for preschoolers.
Tim Smith of Centre for Brain and Cognitive Development, Birbeck, University of London described that distinction as "an oversimplification of the many ways young children and their families engage with screen media".
"For the greatest health benefits, infants and young children should meet all the recommendations for physical activity, sedentary behaviour, and sleep in a 24-hour period", the report states.
But several experts noted that WHO's broad recommendations were based on thin evidence, and chastised the agency for adopting overly simplistic definitions of key terms, notably "sedentary screen time".
One in three adults today are overweight or obese, and one in four adults does not do enough physical activity, she said. 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.