There isn't an obesity epidemic. The average weight of Americans has gone up, but only by about 14 pounds. 14 pounds isn't the difference between thin and obese. It's the difference between manual labor jobs and desk jobs.
The "epidemic" was invented by bad science, and the re-defining of "Obese" to include millions of Americans who were previously classed as "normal" or "overweight".
Look for an article at Cato.org called "The Myth of an 'Obesity Tsunami.'"
There is not an epidemic of obesity. There is an epidemic of intolerance toward fat people.