For me, If I get all the sleep I want, I'm lethargic and unenergetic, but if I get less sleep I'm tired all day (but strangely more energetic). It's like there's no happy medium. I wonder if anyone else has this problem, and if there's a solution.
All have a huge impact for me. I can go on much less sleep when I do hard exercise that day.
Recently, though, I started a linear progress novice strength training program (Squats, Dead Lift, Bench Press, Overhead Press) - three times a week for 40 minutes. My sleep patterns immediately shifted, and I am incapable of waking up without at least 8 hours of sleep on off days, and 10 hours of sleep on the days that I lift heavy.
For the first time in my life, ever, I'm finding myself going to bed at 10:00 PM at night so that I can get up by 8:00 AM the next morning.
Starting Strength is raw lifts involving the entire muscle toolchain until you can't do anymore. It works your body in a total, basic way that most Americans haven't ever done.
So you'll be sleeping alot as your body gets used to it. You'll notice incredible increases in everyday strength--as if the entire world, including you, lost a significant fraction of its mass over the course of a few months--and the desire for sleep will subside.
Of course, I still have my original sleep problem...
(except potentially food. You are a little more efficient at processing food, but if you develop a large amount of muscle you need a lot of food to maintain it)
Experimenting with yourself is cheap, interesting and rewarding. Not always easy, but definitely worth trying.
Also, read Seth Roberts at http://sethroberts.net/self-experiment/ - he (and his reader) report about a lot of experiments regarding sleep and mood; among those I remember: - eating lots of animal fat (bacon and/or butter) improves sleep. Standing on one leg for extended periods of time improves sleep (probably the easiest way to fatigue yourself into sleeping).
Basically the solution is to sleep just enough to accumulate the number of sleep cycles you need to feel rested. We're building a tool to tell our users what that length of time is. I'll write up a post on the thought process/science behind it and put it up tomorrow.
So basically I have to moderate caffeine (for me it is every other day at most and none after 3pm) and get up as soon as I first wake. When I'm very good about no caffeine, regular exercise, and near-perfect diet I require less sleep. Kind of hard to maintain that level of discipline, though. So it's usually 7 hours a night.