Staying up late generally does not make people thinner, but may make them fatter. In terms of energy consumption, there is not much difference in the amount of calories consumed when a person sleeps flat on his back and when he stays up late to work or watch TV dramas. However, when staying up late, a person tends to consume a lot of food without realizing it, because staying up late makes a person anxious, and when a person is anxious, he or she is likely to soothe himself or herself with food. In addition, staying up late causes disruption of circadian rhythms, which disrupts the secretion of an important hormone in our body, known as leptin. An important role of leptin is to speed up the breakdown of fat and increase metabolism while suppressing appetite. When we stay up late, leptin secretion decreases, causing us to have a high appetite and a mild decrease in metabolism. In summary, staying up late not only does not make people thin, but also may make people fat and damage their health. Therefore, it is not recommended to stay up late and to develop regular living habits.