I just have to say that he looks better now than he did in college. I ran against him (way behind him, actually) and he was pretty gaunt back then. The muscle and added weight make him look better. Good for him. He looks like a very fit guy in his 40s.
But to the OP's point, we all get older and most of us gain weight (even if we keep up the running). Kid's sports take the place of a second run in the PM, mental focus shifts to a work project, a glass of wine with the wife becomes more important than the 30-minute post-run ab routine. I think its okay. Keep running and let it make you a better, more well-rounded person. Stay fit, but make peace with the fact that you are aging and may inherit new priorities.