Originally Posted by PR_Glen

p90x and insanity is basically the male version of zumba.. You will lose weight you will build a bit of muscle (not a lot) and in the end if your diet is all over the place you will just be a 'skinny fat' mess.. Basically just deflates the balloon. By building muscle in a gym with heavy resistance you shrink the balloon and lessen your chances of becoming fat again.

I have a couple people on my slow pitch team that lost 30-40lbs+ over the winter doing those workouts, and it helped them a lot, they still have their double chins but a lot lighter. If they don't add in more resistance in there they will gain it all back as soon as they stop those workouts (which is inevitable, even top athletes take breaks). With weight training i can get away with so much more. Building muscle keeps the engine running hot where strictly cardio is just like keeping the engine idling.