Bunge treats a third reason for fasting: the spiritual purpose (p. 94).
Citing Evagrius again, he points out that fasting makes the soul like a high-flying eagle—a soaring soul that rises above the lethargy of gluttony. Like a cleaned mirror, fasting enables us to remove the dust and grime that blurs the vision of God.
In that sense, fasting is an opening so that the revelation of God can more clearly and accurately enter into us to do its work. The vision of God is not obscured by other things. Fasting is a means that enables purity of heart to be realized in us.
Bunge ends his meditations on fasting by reminding us that the form of fasting and its duration will not be the same for everyone. It will depend, he writes, on a person’s strength, age, and the circumstances of his/her life (p. 94).
In that regard, I think of John Wesley, who fasted regularly on Wednesdays and Fridays for more than 60 years. If he came to one of those days and was ill, he would take a little broth to keep his strength up. The value of fasting was (and still is) not the amount of mortification we practice, but rather the concentration of our attention upon God. The value of fasting is not how much we suffer, but rather how much we allow the time we would have spent eating to become time we spend “feasting” on God.