Actually, they are fat because of their car-reliant lifestyle. They don't walk anywhere. It's been that way roughly since WW2 when urban planners thought that by spreading out their cities, they'd mitigate the damage done by enemy bombing runs. This tendency only strengthened in the Cold War, resulting in the huge cities, mega highways and sprawling suburbs Americans are known for today.

On the East Bloc side of the Cold War, civilian buildings weren't built with this in mind. Communist leaders didn't give a crap if civilians died, as they were only mindless slaves and fodder to them.

Posted from my tightly packed concrete commieblock apartment.