By Dennis Thompson
Those who used screen devices for five or more hours daily were twice as likely to drink more sugary beverages and engage in too little physical activity, the researchers found.
As a result, these teens showed a 43 percent increased risk of obesity compared with kids who don't use smartphones or tablets at all. But the study did not prove that high use of these technologies caused obesity risk to rise.
"Parents should be cautious with their kids in terms of how much they're using these devices, especially if you see your child on them several hours a day," said study lead author Erica Kenney. "It is something to keep an eye on and be concerned about, because it could be having an effect on their health."
Kids using a screen device for that amount of time is not that uncommon, Kenney, a research fellow with the Harvard T.H. Chan School of Public Health in Boston, and her co-author found.
One of every five U.S. teenagers spends more than five hours a day on smartphones, tablets, computers and video games, the researchers discovered. By comparison, only 8 percent of kids watch more than five hours a day of TV.
"We know kids are shifting their time away from TV and onto these other devices," Kenney said.
Previous studies have linked excessive TV viewing with increased consumption of sugary drinks, fast foods, sweets and salty snacks -- all leading to a higher risk of obesity, the study authors said.
Kenney decided to see whether this risk also applied to kids who've ditched TV for screen devices.
The study relied on data drawn from the 2013 and 2015 waves of the Youth Risk Behavior Surveillance System, a regular youth survey conducted by the U.S. Centers for Disease Control and Prevention. Researchers reviewed responses from almost 25,000 teens in grades 9 through 12.
The results regarding excess TV viewing agreed with earlier findings, the researchers said. Teens who watched five or more hours of TV daily were nearly three times as likely to drink sugary beverages daily and 78 percent more likely to become obese, compared with kids who didn't watch TV.
But those bad habits also appeared to transfer over when kids used smartphones, tablets or computers. Five or more hours of screen device time every day was linked to a doubled risk of drinking sugary beverages and getting too little exercise every day, and a 74 percent increased risk of poor sleep.
Kids tend to snack too much while using electronic devices, explained Stephanie Schiff, a registered dietitian with Northwell Health's Huntington Hospital in Huntington, N.Y.
"If kids are playing video games on the computer while they're eating, they sometimes don't register an end to their hunger," Schiff said. "Eating can become mindless rather than mindful, and they may not realize they are actually full."
In addition, a more insidious process tied to screen use could be influencing their food choices, Kenney said.
"A lot of the literature on TV and diet and TV and obesity risk really suggests the key factor driving these associations is exposure to advertising for unhealthy things that kids nag their parents to get in the supermarket," she said. "We do know in recent years a lot of the money towards marketing foods and beverages has shifted more towards marketing on social media and video games and things like that."
These electronic devices also share TV's ability to glue kids to a couch, Schiff said.
"Years ago, kids would play in the playground at recess or come home after school and play in their yards or on the sidewalk," Schiff said. "That play has been replaced to an extent by video games, Facebook, YouTube and texting.
"It's not a surprise that childhood obesity is on the rise, since to some extent virtual games have replaced real-time play and interaction, and physical activity has been relegated to fingers and thumbs," she continued.
Kenney recommends getting advice on ways to limit screen time if your child is using smartphones or tablets more than a couple hours a day.
"If they're regularly on these devices for long periods of time, you maybe want to talk with your pediatrician about strategies for how to cut back a little bit," she said.
The new study was published online Dec. 14 in The Journal of Pediatrics.