Your metabolism is when your body takes what you eat and drink and converts it into energy, that’s why if you have a fast metabolism you lose weight, the more they eat the more energy they have. Even if your asleep you will still need energy because it’s in charge of of all your “hidden” functions; such as blood circulation, breathing and repairing old cells. Even if a person were to fast they could also have energy because fasting would cause your body to use old cells in order to gain new ones, that usually how people burn weight during fasting. I hope this helped
