Too little sleep or too much sleep can throw your stress and regulatory hormones out of whack, and may lead to weight gain. A single night of sleep deprivation can increase levels of ghrelin (a hormone that promotes hunger), making you more likely to overeat the next day. Reduced sleep may also lead to fatigue during the day (duh) and less physical activity, which may be another reason why people who regularly don't get enough sleep tend to gain weight.
“For some people, it’s knowing, ‘Typically I eat a whole sandwich,’” says Gagliardi. “‘Now, I’m going to make the decision to eat half a sandwich at lunch and save the other half for my dinner and essentially cut my calories in half. And they feel good about that. They’re not having to do math.” To get started, check out these 25 simple ways to cut 500 calories a day.
"When we’re lacking in sleep, our body’s hormones get thrown off balance which can impact our hunger levels the next day. We all have two hormones that affect our appetite: ghrelin and leptin. When we don’t get enough sleep, our ghrelin levels (the hormone that makes us feel hungry) rise, and our leptin levels (the hormone that makes us feel full) drop. This means that when we’re awake, we tend to eat more but feel less satisfied. Try going to bed a little earlier than usual to avoid this imbalance and remember to remove any distractions that might prevent you from nodding off."