Smart people exercise more than average people.This doesn't mean that every smart person I know exercises regularly. I know quite a few ridiculously intelligent people who don't. But, from what I can see, the average amount of smart people who exercise is much higher than in the average population.
I've been exercising more regularly lately, and my coworkers contribute much to it. As a matter of fact, I just went for an 8km run with half of my group. It turns out that some guys with a PhD in Computer Science can be pretty competitive and this forced me to push myself.
It does feels great after wards, tough.