I studied TaiJi and Taoist arts for many years and there are numerous stories of legendary achieved Taoists who derived their energy from breathing or minimal 'food' intake such as sucking the sap from pine needles. I can't direct you to a particular reference... many of these stories are passed verbally from teachers to students...but I would imagine that if you did a bit of research you might find some more stories similar to the one you posted. I believe some of these people are referred to as breatharians.