If you thought letting your children spend their youth playing videogames and eating Fritos was just good, harmless fun, you're wrong. Researchers at the University of North Carolina (Chapel Hill) have found that kids who lead inactive lifestyles - that means getting less than 20 minutes a day of moderate-intensity physical activity - are 5-6 times more likely to be at risk of heart disease than kids who get the 60 min-, utes recommended by the Centers for Disease Control and Prevention.