I think fitness fanatics should disclosed their BMI when they started the craze. At least around me, the only people really into compulsive running either have serious body weight problems they want to tackle, or were told by their doc that they need to move to avoid some cardiovascular problem. I don't know many slim people into compulsive running.

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."