From Grain Avoidance to Living on Qi

Bigu was understood as a graduated practice rather than a single step: an adept moved from an ordinary diet to one built around specific substituted foods, and from there, in the most extreme accounts, toward the ideal of subsisting on qi alone, breath and vital energy taken to replace food entirely. This end point was described more often as an aspiration credited to legendary immortals than as a literal daily practice most adepts expected to reach, and it sits at the far end of a spectrum that in ordinary practice looked more like an unusual, restrictive diet than a claim to require no food at all.

The practice is documented among the fangshi, the technique specialists and masters of esoteric methods active from the Han dynasty onward, whose repertoire fed directly into what became organized Daoist religion, and it remained part of the vocabulary of neidan, internal alchemy, in later centuries, where physical practices such as bigu were increasingly read as outer supports for an inner, meditative transformation of the body's energies. It survives today mainly as a historical category within the study of Daoist self-cultivation rather than as a living, widely kept discipline.