Children are spending way too much time in front of screens, says the American Heart Association, and it's urging parents to drastically cut the hours their kids are allowed to use their phones, computers, tablets, and video games.

Kids and teens age 8 to 18 spend an average of more than seven hours a day looking at screens. The new warning from the AHA recommends parents limit screen time for kids to a maximum of just two hours per day. For younger children, age 2 to 5, the recommended limit is one hour per day.

Research has linked screen time with an increased amount of sedentary behavior in children and teens. While there is no longterm evidence yet to link screen time to an increased risk of health conditions like cardiovascular disease and high cholesterol, there is mounting evidence that it is associated with obesity, cardiologist and CBS News medical contributor Dr. Tara Narula explains.

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"We think that being in front of a screen, kids start snacking," Narula told "CBS This Morning." "They aren't paying attention to clues that might tell them they're full and don't need to keep eating. They're sort of tuned out."

Children are also exposed to unhealthy food advertising while on their devices. In addition, the blue light from screens can hinder their ability to fall asleep, and lack of sleep may contribute to obesity risk.

Experts acknowledge that limiting screen time poses challenges, especially given how intertwined social media and the internet have become in everyday life.

And of course, not all media and digital technology is bad for children. "Certainly, it can introduce them to ideas, information, current events, even health education that they may not get normally," Narula said. "It can also connect them socially to people who may live far away geographically, like family and friends, and allow them to be involved in school projects and assignments."

However, parents need to be the ones to step in to set limits.

"The point is that parents need to be what we call a 'media mentor.' We really need to be involved in terms of teaching your children that media can be beneficial but this is how you use it in a healthy way," Narula said.

Parents also need to encourage children to play outside and have face-to-face interactions with their peers.

Media-free zones, such as no screen time in the bedroom and media-free times, including no devices at the dinner table, can also be beneficial.

And perhaps, most importantly, Narula urges parents to be fully present when they're with their children.

"When you're with your kids you really need to be good about putting your phone down or your tablet down and talking to them and being engaged because they pick up on exactly what you're doing," she said.