All food is really re-combined Sun energy if you think about it, combined with certain elements from the earth.
It might be possible for really advanced beings to live off elemental energy, akasha, water and sun energy alone, although I can't confirm that. I'm only leaving it as a possibility. It likely also requires advanced techniques.
However, I don't think even the Clergy have reached that level, and that is out of the question for anyone here to try something like this. Proper nutrition is a must, from physical food. You do not want to end up like those "spiritual" breatharians who give meditation and energy work a bad name by fasting themselves to death like fools (and eating food while no one's looking, 99% of them frauds, the non-frauds are dead or on their way to the grave as can be clearly seen by anyone). All that does is harm you physically AND spiritually, while making people sceptical of spiritually more entrenched in their views. Realism and humility of one's limitations are required here.