From the Eleventh Chapter of "The Five Treasures of the Nei Jing" The six fu organs transmit and transform things but do not store them, so they cannot be full. Therefore, if the food is taken into the mouth, the stomach will be strong but the intestines are weak; if it is eaten, the intestines will be strong but the stomach is weak. Therefore, it is said to be real but dissatisfied, full but not real. The function of the six fu organs is to convert dietary water and grain into essence, so they sometimes appear full but cannot stay full forever. So this situation occurs because the water and grains go down from the mouth, the stomach is full, but the intestines are still empty. After the food is transformed, the essence is nourished and stored in the five internal organs, and the dregs go downwards, the intestines are full, and the stomach becomes empty at this time. Therefore, it is said that the six fu organs are sometimes full, but cannot always be full. The five internal organs are always full of energy, not the food and water. As the saying goes, just after eating, the stomach is full but the intestines are empty. After a few hours, the stomach will be empty and the intestines will be full.