'Food Clock' May Override Master Sleep Clock in Times of Duress

"However, this work opens up the idea that while there certainly is a central light clock, and clearly light does 90 percent of the regulatory job, other factors may come into play," he said.

"In fact," Mignot added, "I would say that in most cells in your body, you have a clock, and most of the time, these clocks talk to each other. Because the body is always prepared to anticipate different changes that should happen at certain times of the day. So, I wouldn't be surprise if there's a clock in your skin to anticipate light in the day, and a clock in your kidneys, so you are prepared to go the restroom. It's not just about being tired. It's pretty much every function that's regulated by the time of the day."

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For additional information on sleep and the circadian rhythm, visit the National Sleep Foundation.