It's easy to draw a line from this lack of outdoor free time to the rise in couch-potato-ism that is catching up with our families at younger and younger ages. The CDC reports that the rate of obesity in children between ages two and 19 about tripled between 1980 and 2004. Nearly 19% of 6- to 11-year-olds and more than 17% of preteens and teens are overweight. And, get this: During the school year, kids might be too overscheduled for a walk in the park, but at least their busy. During the summer, when they might be frolicking outside, they're inside instead, frolicking virtually at their Sony ( SNE) PlayStations or gluing themselves to their computers. The result is that they're actually gaining weight over summer vacation, expanding their body mass index twice as quickly as they do during the school year, according to a study that came out last year. In these environmentally fraught times, keeping kids tucked away from nature also makes them less inclined to be interested in it as grownups. A study led by Nancy Wells at Cornell University indicates that kids who have ample "wild" time -- camping, playing in the woods, hiking, walking, fishing and hunting -- before they're 11 are more likely to be eco-aware and eco-responsible as grown-ups. We're not all lucky enough to have untamed wilderness in our backyards. But Louv says that isn't necessary. The main thing is for kids to get outside, ideally for some unstructured time, but some organized time with you is good, too.