Forrest Gump really showed the benefits of running at one level -- a far different one than Zolciak puts out with her post. It might be the least crazy part of her routine and she's far from alone.
The benefits of running or motion in general are pretty clear. It works your cardio, helps to burn calories, and helps to build your body to levels where you can push yourself.
Haruki Murakami captures the benefits and allure of running in his memoirs detailing his own experiences with running and the parallels with his writing -- check it out -- and it really captures how and why someone who runs can do it at this type of frequency.
It unlocks something in you.