There are three main explanations: 1. The method of nourishing the body is adapted to the four seasons, growth is Yang, collection is Yin, so spring and summer nourish the growth of Qi, that is, Yang; autumn and winter nourish the collection of Qi, that is, Yin; 2. Nourishing yang means obeying the characteristics of yang qi growth and making yang qi emit; while nourishing yin means obeying the characteristics of yin qi collection and not making yin qi emit. After listening to the master’s pulpit recently and meditating on it internally, I think his saying is more in line with clinical practice and better reflects the essence of TCM health care. In the spring and summer, everything grows and flourishes with heat, which is Yang in nature; in autumn and winter, everything is cool and closed, which is Yin in nature. People correspond to heaven and earth, follow the natural qi, spring and summer yang qi is strong in the outside and deficient in the inside, autumn and winter yin qi is dominant in the outside and deficient in the inside, people correspond to the four seasons, spring birth, summer growth, autumn harvest and winter storage.