Here’s a distressing statistic: Children spend nearly three times as much time with electronic media than with their parents. Therefore, it is not surprising that TV shows, text messages and music can have a detrimental effect on children’s health. Since ditching the TV or iPod would end in outright revolt, closer parental monitoring is needed.

Researchers from the National Institutes of Health and Yale University reviewed 173 studies, dating as far back as 1980, to look for connections between media and childhood well-being. They were surprised by how many pointed to negative consequences. About 80 percent of the studies found a link between media watching and listening and negative health outcomes. The link between electronic media and obesity was the strongest; that between movies, music, television and sex was the most frequent.

These findings are important because of the pervasive nature of such media today.

The average child now spends 45 hours a week with television, movies, music, video games, cell phones, the Internet and magazines, according to the study. They spend, on average, 30 hours a week at school and 17 hours a week with their parents. As a result, children are picking up a lot from what they watch and hear.

For example, 93 percent of the studies researchers reviewed found that children with greater media exposure have sex earlier. Eighty-six percent of studies found a correlation between media exposure and obesity.

Both links can be weakened by parental involvement. With obesity, for example, limiting screen time and replacing it with outdoor time can encourage kids to be more physically active. Less TV time also means less opportunity to see commercials for junk food and soda.

Discussing sexual activity and its potential negative consequences may appear more difficult than allowing children to learn about it from television shows and networking sites on the Internet, but if parents hope to influence their children’s behavior such conversations are necessary. Just don’t refer to birds and bees.

The project was commissioned by Common Sense Media, a watchdog group, which recommended that parents work with their kids to determine what they watch, hear and play, and for how long.

“It’s as important as going to their parent-teacher conferences or going over their report card,” said James Steyer, the group’s chief executive. “You have to know what Facebook is, and YouTube and MySpace and Twitter are, even though you grew up with ‘Gilligan’s Island’ and ‘All in the Family.'”

These media, of course, have positive attributes. Parents must work with their kids to ensure those outweigh the negative consequences.