I was in a gym at work and guys were doing P90X. It's not an easy program even though they say you can go at your own pace. My son does insanity and running. Again not an easy program. Though as in anything it's how hard it is depends on how hard you push yourself. I think anyone who pushes through either program will get into great shape and lean. No magic to either one but a lot of work with a small amount of rest.
yep it's no easy work,i started out with p90x and found out it's too taxing and switch to regular bb lifting instead.