I haven't really looked into the issue, but Iron Mongrel might be onto something as the much thinner EU countries also have waaaay lazier labor laws. Of course they also have better health care and the U.S. did not always have this problem, so
The thing is you can't really look at it from that angle. They have those labour laws because of the culture they have over there. You can't just impose different labour laws from above and expect things to get better - there has to be a significant change in attitudes over time. Europe has lax labour laws, good health care etc. because they value those things. Though I'm certainly not a big EU booster. There's plenty of things Europe gets completely wrong too.
To be fair, I'm not sure if wholesale cultural change is fully possible. National character and habits are sometimes ingrained so deeply that it continues for centuries, surviving the complete collapse or replacement of government, or even the dissolution of the country as a defined area. Just ask Russia. Or the Middle East. Trying to impose cultural change with mere
legislation may be totally hopeless.
Then again, there have been some isolated successes. The Liberal Party of Canada made multiculturalism a cornerstone of the Canadian identity by ramrodding through all kinds of legislation and backing it up with money, government power, and altered school curriculums and (most importantly) by consistently sticking to those guns for several decades.
That's why I think there needs to be a clear public discussion regarding the obesity epidemic and what says about our culture as a whole. If an issue is publicly dicussed, putting it on everyone's mind and the consequences are of the situation are clearly defined, it goes a long way towards encouraging a true cultural change.