Stephen Dubne proposes a novel theory:
Is it possible that the availability of good plumbing has contributed to our national weight gain? This may sound ludicrous, but think about it for just a moment. Very few people have to trek through the night to use an outhouse anymore; furthermore, restroom facilities are readily available just about everywhere — which means you don’t have to worry about getting rid of your waste, which frees you up to consume as much as you’d like.
Is he shitting us?
The Dish 