There is a natural cycle the body works on and many of you know the term, the circadian cycle or rhythm. I am going to simplify the cycle in this entry but I encourage you to ask your health providers about it, or research further on your own time. This rhythm guides most life on this planet and we are no exception.
Basically, cortisol is the main driving hormonal force behind the cycle which can unnaturally be stimulated with the likes of caffeine, eating and exercise. The natural trigger for this cycle however, is light. The rising sun (or your flashing alarm!) gets it revved up where it sits in high gear until just after noon. It starts to drop precipitously after about 4 pm (siesta time anyone!!) and fading light of the evening (among other factors of course) helps to turn the wheel over to DHEA. When this stage of the cycle starts to take over we are into the rebuilding mode, repairing the damage done by your daily rigours... particularly important if you have a physically (read exercise!) or mentally stressful day.
The take home message here is if you are planning to exercise, eat or stay up late basking in the glow of your TV or computer, you are stimulating the cortisol side of the system which inhibits the ability of your body to switch into repair mode. Dim or turn off the lights after dinner at a decent time, try and get to sleep by 11 PM, (I'm trying for 10, but easier said than done!), and realize that your body is supposed to be at peak repair mode (ie. asleep!) between 2 and 4 AM. Get up early, turn on the lights and crank that body into even higher gear in the morning with some good food and a good bout of exercise after a whole night of rest and repair.
Choose to help your body do it's job staying well!