Will I loose muscle on P90x?

ive been working out for years now. I'm 5'11 , 165 pounds and I have 15.4 in arms with a 4. Back abs. I'm looking to get a more ripped look since I have the muscle but I also have a small layer of fat. All my life Ive learned that circuit training is to loose fat and low reps with high rest periods builds muscle. Since what ive seen of p90x is circuit training, will I loose a good bit of bulk muscle?