It’s been known for decades now that couch potatoes tend to be less healthy than their more active peers. With content moving onto mobile devices, however, it is unclear whether the same link will be maintained for kids and adults who consumer media on-the-go.

A new study published this week in JAMA Pediatrics suggests that no matter what entertainment is viewed on, more of it may mean less-healthy children.

The study provides a link between what researchers call “screen time” and decreased health outcomes in children. Screen time is entertainment consumed through TVs, Computers, tablets, and other devices that use screens.

The study looked at more than 1,300 children enrolled in an obesity prevention program. Researchers collected data from child and parent surveys, school performance, and physical measurements such as height and weight over a seven month period.

The study’s authors found that children whose parents limit their screen time are generally more healthy than their peers who get unlimited screen time. Specifically, the children with limited screen time were seen to get more sleep, have better behavior, and perform better in school. Children observed to engage in more screen time are also at higher risk for obesity.

“When parents are involved it has a powerful protective effect across a wide range of different areas that they probably never would have expected to see,” said Douglas Gentile, lead author of the study and an associate professor of psychology at Iowa State University. “However, parents aren’t likely to notice that putting limits on the children’s media is having these effects seven months later.”

Despite the clear effects of TV time seen in the study, Gentile and his colleagues say that these effects on children are not immediate. Because of this, parents may not realize that their child’s excessive screen time could be contributing to health issues.

“As parents, we don’t even see our children get taller and that’s a really noticeable effect,” said Gentile. “With media, what we’re often looking for is the absence of a problem, such as a child not gaining weight, making it even more difficult to notice.”