Counter point based on my own experience: in Europe the median runner is actually quite slimer than the median non-runner. And I'm surprised to learn it's different anywhere else.

This is such an odd statement to me. It almost sounds like you're claiming running is a scam propagated by the fats.

Anyway as a to counter your annecdote: I ran every day for a decade before some injuries. I was in quite a few clubs and I genuinely cannot think of a single person from those groups who wasn't "slim."