Spending three or more hours a day watching TV, using computers, or playing video games could put kids at risk of type 2 diabetes, a study shows. More time spent staring at screens is associated with diabetes risk in adults — and it looks like the same is true for kids, too.

Researchers in the UK analyzed data from nearly 4,500 children, and found that those who spent more time glued to the screen had biological markers known to increase the risk of type 2 diabetes. These kids showed signs that their bodies weren't as good at processing sugar, a condition known as insulin resistance — the hallmark of diabetes.

“excessive screen time is harmful to people’s health.”

Today’s study, published in the journal Archives of Disease in Childhood, adds to the growing body of research showing that “excessive screen time is harmful to people’s health,” says Mark Tremblay, a childhood obesity researcher and healthy living expert at the Children’s Hospital of Eastern Ontario Research Institute, who did not take part in the study. “It’s discordant with our evolution.” American kids are spending a lot of time in front of the screen. A report published in 2015 by Common Sense Media showed that 13- to 18-year-olds spend an average of about nine hours a day consuming media through computers, smartphones, and TVs; 8- to 12-year-olds get about six hours of screen time a day.

“It appears that we’ve lost the balance that’s necessary for healthy living,” Tremblay says.

Previous studies found that higher screen time is associated with increased Body Mass Index, a measure of body fat based on height and weight, in 9- to 16-year-olds. One study showed that spending lots of time watching TV increases the risk of type 2 diabetes in adults. The authors of today’s study wanted to see if the same is true for children, says study co-author Claire Nightingale, a research fellow in medical statistics at St George's, University of London.

The researchers analyzed data from nearly 4,500 9- to 10-year-old kids from 200 primary schools in London, Birmingham, and Leicester who took part in the Child Heart and Health Study in England from 2004 to 2007. The kids were asked how many hours per day they spend watching TV or playing video games. The researchers found that children who reported more than three hours of screen time per day had 11 percent higher levels of insulin resistance than children who reported less than one hour per day. Insulin resistance — in which muscle, fat, and liver cells do not respond properly to insulin, a hormone that controls sugar levels in the blood — is a known risk factor for type 2 diabetes. Kids who had a lot of screen time also had higher levels of skin folds thickness and fat mass, which are indicators of total body fat, and of leptin, which is a hormone responsible for appetite.

“at some point you’ve gotta say, ‘maybe there’s something going on here.’”

Overall, the study shows that “reducing screen time in children may help to reduce the risks of type 2 diabetes,” Nightingale writes in an email to The Verge. The study has some limitations — it only shows association, not a direct casual link between screen time and diabetes. Because the data was collected between 2004 and 2007, the study also didn’t include time spent on smartphones or tablets, so the result might underrepresent the amount of screen time kids get today.

However, the findings add to the body of research showing that spending lots of time glued to screens might not be the healthiest habit — especially for children. So even though the study doesn’t show a casual link, it’s in line with what other studies are showing and it’s enough to raise some red flags. “When so many of the measures are showing the same gradient, when it’s so aligned with what common sense seems to tell us,” Tremblay says, “then at some point you’ve gotta say, ‘maybe there’s something going on here.’”