Why are obesity rates falling?

EpiAnalysis reports on a recent briefing from RWJF which suggests that childhood obesity may be declining in several locations across the U.S. 

Interesting to note that these improvements took place in a wide range of communities, from wealthy Eastern Massachusetts and New York City to poorer regions such as Mississippi and West Virginia. 

EpiAnalysis discusses some follow-up questions to the study: 

(1) First, if these changes are meaningfully large and sustained, are there clear contrasts in policy we can use as “natural experiments” to analyze what changes might have occurred? 

It's a nice thought, but it seems unlikely that there would be a natural experiment that helps to understand these declines in obesity rates.  In fact, I would venture that there are few single policies that have the capacity to affect obesity rates.  More likely, these shifts are the result of a cultural shift.  We have become more cognizant of the problem of obesity and (slightly) more aware of the ways in which it can be combatted.  I would guess that shows like the Biggest Loser have more effect on obesity rates than school lunch programs or sugar taxes.  

My views on this topic have shifted a lot in recent years and will continue to shift, but I'm increasingly skeptical of paternalistic policies to prevent obesity.  Not because I'm politically or ethically against such policies, but because I don't think we know enough about the causes of obesity to allow us to design precise and effective prevention policies.  Once we have a better scientific understanding of obesity, I will welcome the introduction of better and more targeted prevention policies.