Fasting Analogy

I could have sworn I heard an analogy quoted from a church father of fasting being like an eagle being tied down to a dog, with the eagle representing our spiritual life and the dog representing our flesh and earthly desires. The only way for the eagle to soar was to deprive the dog, and if we kept feeding and indulging the dog/our flesh it would hold down the eagle and prevent us from growing spiritually. Now I can't seem to find this reference or analogy anywhere -- and am wondering if anyone knows the source to this? Perhaps my memory is incorrect?