O chastity, how greatly thy beauty shines, in sleeping on the ground, and in hunger pangs that drive away sleep through the body’s hardship, and through abstinence from food which produces a deep moat between the ribs and the belly! All food and all leisure that we indulge in create and give birth to shameful images and unseemly idols, and these come forth and are beheld in the hidden place of our minds, enticing us secretly to take part in shameful deeds. But an empty stomach makes our thinking a desert land, arid and silent from any turbulent thought. The stomach that is filled to satiety is a place of spectacles and an arena of vile fantasies, yea even if we be alone in the desert. For, it is said, satiety desires many things.
—St. Isaac the Syrian