Every one knows that sleep does a body good. But do you know a few of the finer things of why this is? In short, sleep lets you recharge your body and mind. A common torture method is in fact keeping someone up for days, they mentally go crazy. But for 99.9% of us, were looking at the more common, squeezing in a few days of 6-7 hours of sleep a night.
Lets look at a few hormones and their implication on metabolism and health. When your sleep restricted your level of the hormone cortisol doesn't go down as much as it should as you approach evening, it should be close to nil, when you go to bed. When cortisol stays high your at more risk for insulin resistance.
Another hormone that is affected by sleep restriction is Leptin. Leptin is released by the fat cells that signals satiety to the brain and thus suppresses appetite and lets your body feel full. When your not getting the sleep you need, your levels of Leptin go down, so you will end up ingesting more calories then your body needs. This correlates with an increase in the hormone Ghrelin. Ghrelin increases your appetite. So you lose a few hours of sleep over a few days and cortisol levels don't decrease like they should, Leptin goes down, Ghrelin goes up.
An aside is I just read a study where exposure to artificial light disrupted the circadian cell division in rats. 12 hours of darkness, 12 hours of light. Compared to a group that had an hour of light during the normal darkness time and found that cell division was harmed and a large number of genes was affected.
So what to take from all this, maybe today's obesity epidemic is the result of sleep deprivation. It probably doesn't help that when your not sleeping your not going to the fridge for an organic apple, but a tub of Hudsonville ice cream. Oh, and make your bedroom a cave. Dark and cool.