I think there are a lot of societal reasons for the rise of childhood obesity. The biggest culprits are video games, the convenience of garbage food, and parents that are too busy or irresponsible. Just make sure you kid eats balanced meals and gets 30-60 minutes of physical activity per day. Not very complicated.
Fast food restaurants can be blamed for selling sub par food but not for people continuing to shovel it down their own throats. No one is forcing them to eat fast food consistently. And even when you don't have many other options in your neighborhood, that should be MORE motivation to find something better.
Parents are always the ones to blame when it comes to the health of their children. Kids are not the ones able to purchase the food on a consistent basis by themselves. It's the parents responsibility to educate their children about over consumption and steer them on the path of healthy eating. The restaurant merely sells the food.
They are not forcing the food down the children's throats, they are just making it. I think its up to the media and the parents in order to stop this kind of thing from happening. The world is always going to eat junk food,but the parents have to stop them at an early age.