In my senior year of college, anticipating my wedding, I found myself attentive to weight in a new way, and noticed that when I stayed up late I gained weight. At first it seemed this was because I was likely to eat something at 10 pm, so I thought I must be eating more overall. Then I noticed I was hungrier in the morning when I had eaten late, which seemed weird. And I wanted junkier things. Then I tried exerting some self control and not eating at night when I stayed up late. And the weight didn't come off. Then I started going to be early again and the weight came off by itself. Years later I found out why, and that it wasn't just a fluke of my metabolism, but a well-documented phenomenon.
1) Sleep deprivation, even a couple of hours short per night for less than a week, causes the cells to need significantly more insulin to process the same amount of sugar. So the pancreas works harder, and various other systems are affected by the higher level of insulin. This is thought to be one mechanism by which PCOS, Fatty Liver, and metabolic syndrome develop.
2) Sleep deprivation lowers activity in the Prefrontal Cortex, and thus lowers our impulse control. So you see that hot salty pizza and just WANT IT SO MUCH.
3) Sleep deprivation increases the hormone ghrelin that stimulates appetite and increases fat storage and lowers the hormone leptin that tells you when you're full. Triple scoop, anyone?
4) Sleep deprivation tends to dysregulate cortisol, leading to difficulties falling asleep, fatigue, anxiety, and abdominal weight gain, everyone's favorite.
5) And who wants to exercise when they're tired? And if you power through, you won't be able to go as long or as hard.
This is why whenever a woman asks me how to lose weight, my first question is about her sleep. Getting enough sleep balances mood and cravings, and after a few weeks you might even feel like exercising. Does this ring true for you?