Jason wrote up a post over at Hackszine.com about an interesting study that was conducted over at Harvard Medical School about a second circadian clock in mammals.

There was an interview with Clifford Saper, a professor of Neurology and Neuroscience at Harvard Medical School, in last week's Science Friday. The discussion was about a study which was just published in the journal Science about a second circadian clock in mammals that is driven by food availability. The research suggests that this second clock evolved as a sleep-cycle "reset" mechanism which allows mammals to very quickly adapt to optimize their wake period and maximize the chances of finding food during times when food is scarce.

This starvation override can take effect after only 16 hours of fasting. When the fast is cancelled by a sufficient caloric intake (read: real food), the body will shift its natural wake time to coincide with the event. So if you want to ditch your jet lag, or if you want to get up earlier in the morning, it might be as simple as fasting for the 16 hours prior to the time you would like to wake up, then eat a big meal. Your body will then override its normal light-based rhythm and wake at that same time going forward.