As screens have become pervasive in everyday life, particularly the minicomputers in our pockets, experts are still trying to get a firm grasp on the changes they may be having on our health.

But a clearer picture of the effects of smartphones and other screen-based devices is beginning to emerge.

As far as childhood obesity is concerned, it doesn’t look pretty.

Screen time is making kids more sedentary, and that sedentary behavior is tied to a child’s weight, the American Heart Association (AHA) warns in new recommendations issued last week.

Experts have long warned of the dangers of too much television time and encouraged parents to turn off the TV and get kids outside and moving.

But in recent years, simply turning off the set in the living room is no longer enough.

“I’m surprised at how quickly it’s become the norm, that we have these multiple screens that are ubiquitous and we’re not questioning the harm,” said Tracie Barnett, an epidemiologist affiliated with the University of Montreal and McGill University who chaired the committee that wrote the AHA report.

“It’s sort of become part of the landscape and that’s it,” she told Healthline. “But it’s quite a significant jump compared to 10 years ago… It’s not just that we’ve replaced what we view TV content on, but overall it’s really exploded, because now you’re being bombarded.”

The numbers don’t lie

The AHA report points to stats that say while time spent in front of the TV appears to have decreased, screen time as a whole has increased and is likely to continue to grow.

A report from San Francisco-based Common Sense Media concluded that 13- to 18-year-olds are spending an average of 6 hours, 40 minutes on what it terms “screen-based recreational media.”

That includes watching TV content and other movies and videos, browsing the internet, spending time on social media, and playing video games.

Preadolescents are averaging more than four hours a day.

And these numbers don’t include time spent on screens for schoolwork.

In total, the AHA says, school-age children are sedentary for about eight hours a day, and most engage in what it deems excessive screen time.

That increase in screen time carries numerous risks, the AHA says, including decreased sleep quality and social skills as well as increased risk of health issues associated with sitting for long periods of time, such as obesity.

Researchers also point to a study that found children who spent more than 35 hours per week of screen time faced greater risk of heart disease and stroke compared to those who spent less than 16 hours per week.

Other groups have come to similar conclusions.

In an open letter published last week, 50 psychologists called on the American Psychological Association to take a stand against the work being done by tech companies and psychologists working for them that uses “hidden manipulation techniques to hook children on social media and video games.”

Psychologists’ role in developing “persuasive technologies,” they write, “contributes to health risks associated with kids’ overuse of digital devices.”

Getting physical

The American Academy of Pediatrics (AAP) says screen time should not displace physical activity, exploration, or social interaction.

David Hill, a professor of pediatrics at the University of North Carolina School of Medicine and director of the AAP’s Council on Communications and Media, says the new AHA conclusions reflect the current knowledge in the field.

“In short,” he told Healthline, “the link between screen time and heart disease almost certainly runs through obesity.”

Hill adds that not all screen media are necessarily implicated, noting that watching TV and similar content appears to have much worse effects than, say, playing video games.

There hasn’t been an established link between obesity and gaming, he said, and it appears that snacking while watching and exposure to ads for unhealthy foods may be the driving factors that make watching TV particularly bad.

“I think it makes sense to assume those data will hold regardless of the size or shape of the screen” on which kids are watching TV, he said.

The AHA report also concludes that obesity risk from screen time often persists, despite increasing physical activity or adjusting diets.

How to reduce children’s screen time

The biggest way to avoid those effects is limiting screen time itself.

In fact, Barnett says parents shouldn’t use their phones or other devices when they’re with their children.

“It implicitly gives them the message that’s it’s OK and that we can be interacting with our phones instead of with each other,” she said.

Barnett also recommends zero screen time during mealtimes or in bedrooms and no screens for kids under 2 years of age.

She concedes that “quality” screen time when a caregiver is interacting with a toddler during a show may be OK in limited amounts. However, she adds, “regardless of whether sedentary time is spent with parents or not, it still contributes to sedentary time.”

Hill says he recommends no screens before 18 months of age, although something like video calls with Grandma would be OK.

“I always ask, ‘What’s the goal?’” he said.

Reasons such as “because their friends are all doing it” aren’t acceptable, Hill says. He notes the AAP offers a planning tool to help parents set the right amount of screen time.

How to reduce kids’ screen time

  • No devices for really young children.
  • Limit the daily hours for older children.
  • Don’t overuse mobile devices in front of children.
  • Make alternatives to screens more appealing.

Childhood obesity has been on the rise in recent years, but researchers are beginning to see what they think might be a plateau, Barnett says.

And she thinks it’s a problem that’s solvable.

The biggest impact could come from making alternatives to screens more appealing.

She says that may prevent kids from wanting to stare at their screens as much in the first place.

“Way back when, it was a lot more fun to go outside than to be indoors. And now it’s more fun indoors,” Barnett said.

She’d like to see that change, perhaps through making parks more fun and interesting for children, including through utilizing children’s input on designs.

And some of the answers may come from screens themselves.

These include apps that encourage users to get outside and reinforce “positive ways of using screens,” Barnett said.

She says “screens are here to stay,” and the question is how to incorporate them in more positive ways.

But the biggest sign of hope she sees is that parents are becoming more aware these new generations of screens are contributing to sedentary behavior — just like the less mobile televisions of decades past.