Maps that plot obesity levels by state circulate occasionally. Here is one that suggests it is the "red" states or even the more rural states that have the biggest problem.
Other investigators have been loooking for ways to link "urban sprawl" to levels of obesity. Here is a prominent example.
But the democratization of luxury has been widely noted, as has obesity among poorer Americans. Gorging oneself was once a sign of wealth proudly displayed. Bill Bryson offers detailed descriptions of the meals consumed by wealthy Victorians.
So what do we know? Wealth does not guarantee happiness -- but it beats being poor. Affluence does not guarantee long life or a slim and healthy appearance -- but it beats hunger. Who ever expected unmixed blessings?
UPDATE
I just found this.