Fasting should be chiefly mental (abstention from thoughts). Mere abstinence from food will do no good, it will even upset the mind. Spiritual unfoldment will come rather by regulating eating.
But if, during a fast of one month, the spiritual outlook has been maintained, then in about ten days after the breaking of the fast (if it be rightly broken and followed by judicious eating) the mind will become pure and steady, and remain so.
In the early days after my coming here, I had my eyes closed and I was so deeply absorbed in meditation that I hardly knew whether it was day or night.
I had no food and no sleep. When there is movement in the body, you need food. If you have food, you need sleep. If there is no movement, you do not need sleep. Very little food is enough to sustain life. That used to be my experience. Somebody or other used to offer me a tumbler of some liquid diet whenever I opened my eyes. That was all I ever ate.
But remember one thing: except when one is absorbed in a state where the mind is motionless, it is not possible to give up sleep or food altogether. When the body and mind are engaged in the ordinary pursuits of life, the body reels if you give up food and sleep.
There are differing theories concerning how much a sadhaka should eat and how much he should sleep. Some say that it is healthy to go to bed at 10 p.m. and wake up at 2 a.m. That means that four hours sleep is enough. Some say that four hours sleep is not enough, but that it should be six hours. It amounts to this, that sleep and food should not be taken in excess. If you want to cut off either of them completely, your mind will always be directed towards them. Therefore, the sadhaka should do everything in moderation.
There is no harm in eating three to four times a day. But only do not say “I want this kind of food and not that kind” and so on. Moreover, you take these meals in twelve hours of waking whereas you are not eating in twelve hours of sleep. Does sleep lead you to mukti? It is wrong to suppose that simple inactivity leads one to mukti.
— Ramana Maharshi