From a Scientific American Mind (September/October 2009) that I finally got to after it hung out for 4 years in my bathroom “library,” re a study by Motivala et al published in May 2009 Psychoneuroendocrinology:
Sleep mediates ghrelin and leptin levels. Ghrelin is a hormone that increases hunger, while leptin promotes feelings of fullness. Sleep deprivation wacks these hormones out & results in cravings of carb-rich, high-calorie “comfort foods.”
Furthermore, the brain secretes growth hormone during the deep-sleep phase, helping the body convert fat to fuel. Without enough deep sleep, fat accumulates.
My guilty midnight snack (when I intended to go to bed at 9:30 because I about konked out in meetings all day) is crunchy peanut butter on graham crackers (preferably chocolate) with apple juice. When I’m counting Weight Watchers points (don’t judge–I dropped 30 lbs a few years ago, & it felt great…it’s nice to feel great sometimes), that blows the day.
I have never heard of ghrelin before so I Googled it to learn a bit more. Named as shorthand for growth hormone release inducing (like endorphin for endogenous morphine). Made all over the body, which suggests it has a whole buncha functions. It is integral to cognitive adaptation & learning in new environments. Is this why newness (& parties full of strangers) are so overwhelming & emotionally depressing when I’m tired? Parties should be at the beginning of the day when I’m rested & can handle them. My wife practically has to crowbar me out the door to go to them at night (since she knows everyone & is not overwhelmed & I am the wallflower of the pair–hard to believe, I know).
Ghrelin is the first/only known circulating appetite-activating hormone? This happens in the hypothalamus. Sensitivity of mechanisms in hypothalamus to ghrelin are leptin- & insulin-sensitive. This makes sense. It also activates the cholinergic-dopaminergic reward link, which basically makes food yummy & makes us want more. OK, I’m following. It also makes alcohol rewarding…Hmm, so blocking it could help alcoholism (it doesn’t say this–I’m extemporizing) & obesity, but it would make food unrewarding. I am a big liker of food. That is a tough one.
Here’s another interesting factoid parsed from the bio-speak. It may undermine “mechanosensitivity of gastic vagral afferent,” which means your brain doesn’t hear your stomach screaming, “DUDE, STOP EATING THAT TARDIS CAKE YOU MADE FOR THE KIDS BIRTHDAY! WE’RE ABOUT TO BURST DOWN HERE!”