Morning sunlight exposure triggers proper metabolism, sets a timer for sleep approximately 16 hours later, suppresses melatonin, and interacts with the adenosine system to mitigate residual effects of insufficient sleep.

“But it's that diffuse, very bright sunlight, that photon energy, that you really want that's going to set all the rhythms of your brain and body in the proper way. Not just that cortisol peak, but it's going to trigger proper metabolism, it's going to set a timer for you to be able to fall asleep about 16 hours later, and on and on and on. And I should mention within the on and on and on, it's also going to suppress any melatonin, a hormone that makes you sleepy that happens to be swimming around in your bloodstream at the time you wake up. It does a number of other things too, including interact with the adenosine system and kind of wash out some of the adenosine that might still be residual if you didn't sleep enough.”