I think there's an interesting line drawn towards extreme environments, and the way I define extreme is through a sense of otherness. Or foreignness.
My husband is such a healthy eater. Except when it comes to sweets. He never consumes anything except fruit until noon. And then from noon on he might have some brown rice and some tofu, and then, come eight or nine at night, he orders three mud-pie double-chocolate pieces of cake and eats all three of them.