I've heard it said that one hour of sleep before midnight is worth two hours after. If you go to bed at 10 pm - which also seems to be the recommended time designated in the suttas for lying down and taking rest - then rising at 5 am or even 4 am becomes easy, so long as you go to bed without lots of (or preferably, any) food in your stomach (which in my experience disturbs sleep and also means that one's digestive organs (including the liver) don't get to rest).
Regarding having to have an empty stomach, my recommendation for a rumbling tummy at bedtime is some hot milk with spices and honey if you wish, which alleviates the hunger pangs, helps one to get sleepy, but is soon digested and won't disturb one's sleep. But it has to be hot, not cold. I've been drinking organically produced, unhomogenized milk in this manner and it's been great for this purpose.
If you are finding the early hours hard to adjust to as regards wakefulness, remember also that as a temporary measure, some coffee or tea first thing in the morning doesn't break the five precepts. They do have their uses sometimes.