I've been guilty of some late nights before, and even all nighters now and again to get a ton of work done. One thing I noticed was that my appetite would get seriously messed up each time I did this. When I'm under 8% body fat and eating extremely strict, even small variances in my appetite are blatantly obvious. The most notable thing that I've encountered was that I would be hungrier more often. The end result would be me having a more difficult time adhering to my diet or overeating and making no progress for the day that I under slept. If you read my article about leptin levels, you'll know that leptin is a hormone produced by the body responsible for appetite regulation and suppression. When you eat a calorie surplus, more leptin is produced. And when you diet in a steep calorie deficit, your leptin levels plummet. When you are sleep deprived, your body's leptin levels dive bomb and induces a state of heightened hunger. In addition, ghrelin levels (a peptide secreted in the stomach that stimulates appetite) increase when you don't get enough sleep. So when you don't get enough sleep, these 2 crucial factors that keep you from binge eating start working against you and get thrown totally out of whack. Fortunately, once your sleep pattern returns to normal, these levels will also return to homeostasis fairly quickly. Don't make your body work harder than it has to and make sure you get enough sleep every night if your primary goal is fat loss. To make your workout sessions better and melt fat off like butter, get Red Burner to boost your energy without causing you to crash.