BoingBoing cites a new study showing that suburban living makes you fatter. Or, more to the point, people who live in high density neighborhoods interspersed with shops and services are ten pounds lighter, on average, than people who live in the cul de sacs.
This insight is somewhat along the lines of the Amish Diet— consume 3,600 calories (about 50% more than most people consume) and walk 15 miles a day.