Excessive Aerobic Training: The Exercise Equivalent of a Cheeseburger?

This is from Kevin Helliker writing for the Wall Street Journal:  

Endurance athletes have long enjoyed a made-of-iron image. But amid mounting evidence that extraordinary doses of exercise may diminish the benefits of modest amounts, that image is being smudged. That extra six years of longevity running has been shown to confer? That benefit may disappear beyond 30 miles of running a week, suggest recent research. 

The improved blood pressure, cholesterol levels and robust cardiac health that exercise has been proven to bestow? Among extreme exercisers, those blessings may be offset partially by an increased vulnerability to atrial fibrillation and coronary-artery plaque, suggest other recent studies.... 

"Heart disease comes from inflammation and if you're constantly, chronically inflaming yourself, never letting your body heal, why wouldn't there be a relationship between over exercise and heart disease?" said John Mandrola, a cardiac electrophysiologist and columnist for TheHeart.org.... 

For its subjects, the study concludes, "Excessive exercise significantly increases mortality."