It is our unquenchable desire for more–we know not what ‘more’– that drives us to seek God, and it is this same desire that drives us to make room for Him through the practice of asceticism.
I fast not because food is bad, and not because I want to lose weight, but because I want to be hungry for God. By fasting physically we are reminded that our bodies are not disconnected from our souls and minds. We are little tri-unities of body, mind and spirit. What we do with our body affects our minds and souls. What we do with our mind and spirit affects the health of our body.
When my body is hungry it can be a holy hunger. When my stomach aches with hunger my soul yearns for the living God. When I cry in the wilderness for food, my soul leaps up to eat the bread of heaven and drink from the cup of eternal salvation.
That is one of the most edifying comments on the nature of fasting I have come across. Even if I have given out advice on fasting myself many times before, it is always helpful to be reminded of my own purpose.