leaders in obesity

I'm still not sure what has led the U.S. to become such a leader in obesity.  I suspect that there are a variety of factors like our corn-based diet, our suburban car-driven lifestyles, our comfortable lifestyles and even our massive marketing infrastructure that convinces us that "we deserve a break today" every day.  I know that as a resident of Seoul, South Korea, I see obese people much less often than I do in the streets  sidewalks parking lots of my midwestern home state.  I wonder if our ideas about "liberty" and individualism also allow us to make the wrong choices without the social consequences that one would experience in a more communal society.  Here in Korea, it seems to me that people define someone as overweight a lot more strictly than in the American midwest, but perhaps this is because people are involved in each others lives in ways that would be considered intrusive in my culture.  I also think that living in a place where driving is actually a pain means that we drive less and do a lot of our shopping about 100-500 meters from our crampt apartments means that we buy less and walk more than I did even in "downtown" areas of midwestern cities.  If midwestern cities didn't zone shopping away from housing, perhaps there would be a bit less obesity and a little more community.  On the other hand, if there is another major oil crunch we might discover that the way we've been living (suburban sprawl and car culture) is just not practical anymore.  It wouldn't be "doom" in my opinion even if we have to give up cheap gas, cheap energy and even air travel.  Maybe we could get back to things that matter.  Sounds like a "conservative" paradise, even though todays "conservatives" might not be able to recognize it.