You know, when my friends come to visit Manhattan, they are shocked at the lack of fat people. Well, I tell them, a fat person could never survive in the concrete jungle. For starters, most of the subways are two to three to four flights underground - and that is a lot of walking. I mean, you might start out fat if you move to Manhattan, but you would get thin mighty quick.
In fact, I see a "fat to skinny" reality show - put two fatties in Manhattan for six weeks and see how much weight they lose.