While we sleep, our organism secretes leptin, the hormone that normally lets our body know that we have eaten enough. When we stay awake longer than we should, our body produces less leptin, and we feel a craving for more carbohydrates.

When we eat, the body produces leptin to give us the impression that we are full. But leptin inhibits the production of hypocretin. In other words, the more leptin there is in the brain, the less hypocretin and the greater the feeling of drowsiness.