It's sad really.
When parents lead a sedentary and unhealthy lifestyle, kids are bound to pick up on the bad habits.
I'm not saying to blame it on tv, or video games or junk food. All of that is just fine, but in moderation. Kids also need a healthy balance of outdoor activities, good food, and socialization.
It's up to the parents to instill this in their children.
And the society of 1st world countries, I have noticed, is all about convenience and comfort. This of course is quickly spreading to developing countries, too, but not as much as in North America and other places.