Looks like moms across America have been validated. All the warnings issued to their kids that "TV can rot your brain" just might be true -- sort of -- after all. At least, according to a new study it can.

Watching television has already been linked in studies to an increased risk of heart disease and obesity. But many of those studies included participants who were already overweight. Now, a new study examined TV's impact on longevity with participants who started the study at a healthy weight and had no prior history of heart disease. And the numbers aren't good.

The study, published in the current issue of Circulation, a journal of the American Heart Association, says each hour a day spent watching TV was linked with an 18% greater risk of dying from cardiovascular disease, an 11% greater risk of all causes of death, and a 9% increased risk of death from cancer.

TV watchers who spent more than four hours a day showed an 80% greater risk of death from cardiovascular disease and a 46% higher risk of all causes of death, compared with those who watched fewer than two hours a day, suggesting that being sedentary could lessen your longevity.

The researchers weren't surprised all that sitting doesn't help your muscles any. Doctors say muscle contractions are necessary for vital processes like breaking down glucose and using it for energy.

While no one is suggesting you toss the flat screen you just got for Christmas, experts do suggest giving the remote a break.

"Aim to spend as much time exercising as you do watching TV in an average weekday," suggests personal trainer Simone Manuel of Los Angeles. "Even better, skip watching TV for a day now and then and use that time to take a walk, ride a bike or throw a ball for your dog. Anything that gets you moving."

Can't go a day without the telly? Manuel says if worse comes to worse, pair it with activity. "Move the elliptical or treadmill in front of the television so you can get off your butt while you're flicking through the channels," she says.

Gina Roberts-Grey is a freelance journalist who, in the hopes of increasing her lifespan, took this advice to heart and designated one TV-free day a week.

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