.
Perhaps it also depends on each individual's body (and its comfort zone) as well.
For my one office buddy, he wakes up, instantly springs out of bed (almost doing back flips across the room) and does a 1 hour cardio session before eating breakfast. He's a morning person and for him, the earlier he wakes up, the better. re: Any time after 5:00 AM is sleeping in. After exercising, he has a small breakfast and a larger size AM snack. Thus, even distribution of morning calories / carbs - after his body exercises.
For me, I'm NOT a morning person. Never was and probably never will be. The later I can sleep in, the better. 9:00 AM is my normal winter season wake-up time. For my body, it feels best to exercise AFTER breakfast. re: Between 10:00 - 11:00ish window. If I exercise before breakfast (or before 9:00 AM), my body feels "over drained" the rest of the day. Thus, I don't have remaining energy for my normal noon time and dinner time exercise sessions. Over drained because I exercised too early in the morning.
As a suggestion, perform one's morning exercise time (before or after breakfast) for your unique body's "comfort feeling". If it likes exercising after smaller size breakfast, go for it. If it likes exercisting before breakfast meal, do it instead. If something is "comfortable" on your body, one will continue to perform that exercise daily routine for longer period for much longer calender time.
Hope this helps as well...
.