Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 3
To make your sadhana depend upon not eating is to make a great mistake. When people fast like that, they get into an abnormal condition and can easily mistake imaginations and delusions for 
true experiences. Much fasting in the end weakens the nervous system. So you must drop this habit of not eating for days together. For Yoga it is a mistake to eat too much but a mistake also to eat nothing or too little. If you eat too much, you become heavy and tamasic; if you fast or eat too little, you excite the vital energies and finally overexcite them, but at the same time you weaken the body and the nerves; both are bad for sadhana. You should eat regularly a moderate but sufficient amount of food; it is only if there is illness or disturbance of digestion that a low diet or not eating sometimes becomes necessary, but fasting even for the purpose of resting the stomach should not last more than a day.
For your sadhana you have to use, not outward means like this, but quietness, sincere peaceful aspiration, openness to the Mother.