Sprawl and Obesity
Many decades ago, children could walk almost anywhere they wanted to go on a day to day basis. It was a short walk to school, to a friends house and maybe even to the park. Kids spent lots of time outside socializing and wandering from place to place with friends. Today this is no longer the case. Kids can hardly get anywhere without the help of a car. It's making kids gain weight.
The first study on sprawl and obesity was published in 2008 and it confirmed that residents who live in car dependent communities tend to weight more. One way to show this trend is the increase in school bus ridership. As school have become further and further from residences, children have needed to travel further and now about half of school-aged children ride the bus every day to get to school.
What do we do?
There is no simple way of solving this problem because really there are two problems, obesity and sprawl. The relationship between the two is not perfect; there are other factors which influence both sprawl and obesity. But one clear step that can be taken is moving people back into cities. Reducing dependency on cars increases walkability and decreases sprawl at once. However, even urban living does not really solve the problem. Some cities like New York and Boston are well suited for walking while others require you to use a car for almost everything even if you live downtown.
Sometimes it is better to recognize that you have a problem before trying to search for a solution. These issues are complex and need to be fully understood before halfheartedly attempting to resolve them.