I researched this question prior to beginning P90X so those that are working out in the morning may also be wondering this.  I was concerned that if I did not eat before my workout that my body would use muscle as energy causing them to shrink which obliviously was not my goal. This is what I found…

If you are eating correctly, you will have enough glycogen stores (stored energy) to get through an hour-ish workout….so yes, you will be fine.

Once I get myself out of bed, I literally walk downstairs to workout.  I usually start my warm-up in a matter of 2-3 minutes from the time I get out of bed. I always make my P90X recovery drink the night before so I drink it immediately following my morning workout. There has been a couple of times during "plyometrics" in particular that I did not feel like I had enough gas in the tank to finish so I drank about a quarter of it during the workout. Not sure if it was mental or not but it definitely helped me finish strong. If you do decide to workout on an empty stomach, it’s almost mandatory that you should have some sort of recovery drink right after. The recovery drink will not only replenish your glycogen stores that you used up during exercising but it will also stop the breakdown process of your muscles as well as stimulate muscle repair and growth.