Why is it not light and heavy in winter?

Why is the weather not as light as in winter, and why is it heavy in winter? It is cold in winter and the temperature drops. In order to keep the body temperature constant, the human body will instinctively store more fat to resist the cold. Therefore, the speed of human fat synthesis and metabolism is accelerated, while the speed of fat decomposition is reduced a lot because of the temperature drop. In this way, the rate of fat synthesis is high, and the rate of fat decomposition is also high, so that fat accumulates and becomes fat. This is a natural physiological phenomenon. Don't worry too much about this situation of getting fatter in winter, and it will naturally recover in summer.