Bigu means not to eat grains, which is equivalent to not eating fireworks. It is a method used by Taoist priests to cultivate self-cultivation. Usually, when crossing the valley, don't eat food roasted with fire, just drink water and eat some natural foods, such as mulberry and Polygonatum. In addition, many other religions have similar methods of self-cultivation, such as Tibetan Buddhism.

When the scientific civilization has reached a certain height, few people in modern society believe in and practice this ancient health-preserving method, and almost no one can break through the human survival limit of fasting for 7 to 10 days or fasting for about 30 days under strict scientific experimental environment. Some hunger strikers seem to be able to go without food or drink for days, but they are all carried out under the environment and conditions set by the performers themselves. People who can go without food for a long time usually only limit the types and quantities of food, and it is impossible to fast or ban water for a long time. In the case of fasting and water shortage, human life depends on the actual measured basal metabolic rate, the storage of sugar, fat and protein in the body and the functional status of various important organs. At present, there is not enough research to draw a conclusion on this issue.