I always do my workout before eating breakfast, as I feel that is the best time to workout for me. Keep in mind this is not for everyone and you should always consults your doctor before starting an exercise program like P90x, as well as ask your doctor if a before breakfast workout is the right best time for you. If you are disciplined enough to do your workout in the afternoon this can be more effective for more intense workouts, as you will have more energy. Just be sure to not wait too long in the day and end up missing the workout you had planed to do.
The downside to completing your workout in the morning is that you may be tired from just having woken up. You will also most likely have an angry stomach growling as you workout. I still like to do it this way as my stomach is empty so I feel I will be burning calories that are stored as fat rather than from the food I have eaten.
Follow along in part 2 tomorrow.