Fasting for selfish reasons

Just came across a great saying on fasting. I have often been asked by Protestant Christians why we, as Orthodox Christians, fast. The response by Bishop Kallistos Ware to this was very simple. People are all too often willing to fast from food for all sorts of selfish and vain reasons: to diet, to lose weight or to improve health. So why are we not willing to fast for the benefit of our souls?