I'm thinkin' of tryin' some HIIT after seeing Turbo Fire last night. You can do two days of HIIT only if doin somethin like Insanity.
Imo I wouldn't recommend running 7 days a week as it can prone you to injury and after awhile your body can reach an muscle exhaustion effect and you won't look near as good as you should. You ever see those semi skinny guys hat run for an hour a day but looks like their getting no results? That's the reason why. It's recommended to do resistance training into cardio for best results due to what Ring just said (burns more calories over time and gives you nice results).
If you do run for the 7 days a week and keep to this routine, hit me up a month later and tell me how it's been goin for you. If you start to pleateau I can start thownin some more info your way.
The reason why I haven't said too much yet is for the fact that I want to see if these routines will actually work for you and if what I've been doin will get you better results. I'll still throw my two cents in but if you start to pleateau let me know and i'll work with you to get you in the best shape of your life!