This is pretty heartbreaking. According to a new Harvard study, researchers found that children with better educated parents are also less likely to become overweight:
In 2003, 86.6% of adolescents living with parents who had college degrees told survey-takers that they had exercised or played a sport for at least 20 minutes continuously sometime in the last seven days. By 2011, 90.1% said they had done so.

By contrast, 79.8% of adolescent children with parents who did not go beyond high school said in 2003 that they had exercised or played a sport for at least 20 minutes in the last week. By 2011, the numbers of those adolescents who had done so had barely budged, standing at 80.4%.
The thing about the fight against obesity is that many people assume that the quickest fix is to burn more calories than you consume.  But what they tend to forget is that it also has to do with genetics, metabolism, cultural and environmental factors. 

And while the lack of exercise in poorer households is definitely part of the problem, this is often exacerbated by little access to affordable healthy food, which is something that most financially strapped families have to deal with on a daily basis.