From the sayings of StSyncletica about Fasting

"Just as the most bitter medicine drives out poisonous creatures so prayer joined to fasting drives evil thoughts away."

"Do not let yourself be seduced by the delights of the riches of the 
world, as though they contained something useful on account of vain pleasure.  
Worldly people esteem the culinary art, but you, through fasting and thanks to cheap 
food, go beyond their abundance of food.  It is written: 'A satisfied soul loathes the honeycomb, but to a hungry soul every bitter thingissweet. [Proverbs 27:7].