Good news (sort of): Overall obesity rates in children seem to be stabilizing. Rates rose from 1998-2003 but did not change much from 2003 to 2007, with one exception: rates are still rising among American Indian/Alaskan Native children. Here's a map of childhood obesity rates by state (thanks to the Wall Street Journal). Rates are decreasing in a few states! Oregon has the lowest rates (less than 10 percent). Mississippi has the highest (21 percent).
Overweight children are more influenced by advertisements for branded products than are average weight children, according to a pilot (preliminary) study in Appetite. Evidence for restrictions on advertising? I think so.
The CDC has produced a policy-wonkish suggestions for what communities should do to make it easier for people to eat less (or better) and move more. Examples: "Communities Should Provide Incentives to Food Retailers to Locate in and/or Offer Healthier Food and Beverage Choices in Underserved Areas," and "Communities Should Improve Availability of Mechanisms for Purchasing Foods from Farms." These are all good "shoulds." The report gives ideas for measuring the success of such initiatives but does not discuss how to implement them, alas.