The largest difference is movement. Which helps keep down obesity in many other nations: If you walk everywhere, or bike, or use transit for 90% of what you do, you will burn a lot more calories (especially grocery shopping and carrying them home via the metro).
Compared to driving everywhere, sitting at work, etc...
That study is indeed interesting. I just skimmed through it and read the abstract, definitely interesting.
The question now is, what is it? Could it be that the difference in food – not just caloric value of intake – has an influence? Did people start eating more prepackaged foods? If yes, what specifically influenced it? Why did it not influence Europe nearly as much?
Compared to driving everywhere, sitting at work, etc...