Don't go to the doughnut shop when you're sleepy. Being tired heightens your impulsivity, so you're more likely to grab the cream-filled with chocolate icing. In a double whammy, lack of sleep also disrupts the digestive system, especially two hormones, leptin and ghrelin, which help regulate hunger. You're more likely to crave carbs, and at the same time your metabolic system has slowed down. That midnight pizza, along with the doughnut, will be stored in your hips rather than metabolized.
— Frederick Brown