I read about a person (Prahlad Jani) who is living without food and water for 50+ years. I was curious about the feasibility and came across the concept, breatharianism. Good concept to understand (fasting is time bound but breatharianism is forever). Wikipedia has good explanation and couple of other websites has more details. As mentioned in a website, humans needs practice to reach the final state (current state, vegetarian, vegan, raw foods, fruits, liquids, and then prana). Time taken to final state depends on individual (every human is unique). There are several explanations like prana, liquid light, life air, etc. and there are religious explanations as well from various religions. There are instruments commercially available to extract water from air, probably people following prana may get liquid sustenance through air.