The Exercise Equivalent of a Cheeseburger?

I read an interesting article in the WSJ today about the dangers of endurance exercise.

Basically it's saying that people who run over 30 miles a week have an “increased vulnerability to atrial fibrillation and coronary-artery plaque” versus non-extreme runners.

Seeing as how I can barely motivate myself to run five miles a week, it doesn't really apply to me, but it's definitely worth reading.