Here are 4 perspectives on fasting:
1: Fasting and Christ
Fasting is connected with Christ’s absence (Mt 9:15). Thus it is a law that no one fasts on Sundays or 50 days of Paschaltide. Denying material food, which nourishes our body, nurtures an interior disposition to listen to Christ and be fed by His saving word. Through fasting and praying, we allow Him to come and satisfy the deepest hunger that we experience in the depths of our being: the hunger and thirst for God. We abstain during to the 40 days of Lent to prepare for the alleluia during the 50 days of Easter. Just as the Eucharistic fast orients us toward receiving Him at Mass, our fasting orients us toward the heavenly banquet. The ultimate goal of fasting is to make the complete gift of self to God.
“To abandon, for God’s sake, all worldly enjoyments, has always been the practice of holy souls” — St Alphonsus de Liguori
True fasting is to be converted in heart and will, “abstinence not only from food but from sins” St John Chrysostom said.
2: Fasting and Spiritual Warfare
Jesus asked his disciples to use fasting as an important spiritual weapon to achieve spiritual victories (Mt 17:21, Mk 9:29, Lk 2:37). Jesus fasted for 40 days and 40 nights to begin his ministry of exorcism. We all need to develop the habit of saying no to ourselves, and this is acquired only through regular spiritual exercises — namely through fasting. Fasting is a spiritual arm to do battle against every possible disordered attachment to ourselves.
“Likewise all who set out to follow in His footsteps make the beginning of the struggle upon this foundation. For this is a weapon forged by God, and who shall escape blame if he neglects it? And if the Lawgiver Himself fasts, who among those who keep the law has no need of fasting?” — St Isaac the Syrian
“The enemy stands more in awe of those whom he knows can fast.” — St Francis de Sales
3: Fasting and distrust of self
The aim of fasting is to give up on yourself and be led to humility. To feel the extent of your own helplessness and desire God to come to your rescue. It is in our weakness and emptiness that the power of Christ is most active and manifest.
Fasting is not an act of mortification for mortification’s sake. On the contrary, fasting for a Christian should be a joyful experience, because it is a self-discipline that we voluntarily impose upon ourselves in the ongoing effort to simplify our lives, to reconquer interior unity, order and freedom, to struggle to overcome our sins and to grow in love and communion with God and others.
Tip: We should never eat to satiety but always rise from the table feeling that we could have taken more.
“Fasting is a spiritual arm to do battle against every possible disordered attachment to ourselves.” — Pope Benedict XVI.
“Fasting finds us as slaves and prisoners and loosens the bonds and delivers us from the tyranny to restore us to former freedom.” – St. John Chrysostom
4: Fasting and Charity
Fasting is an aid to open our eyes to the situation in which so many of our brothers and sisters live. Voluntary fasting enables us to grow in the spirit of the Good Samaritan, who bends low and goes tot he help of his suffering brother (PB XVI Deus Caritas Est).
Fasting is much more than penance. Fasting has two aspects: physical and spiritual. When we fast we deny our bodily impulses, our spontaneous appetite for food and drink, not because these impulses are in themselves evil, but because they have been disordered by sin and require to be purified through self discipline. Fasting confronts our tendency to grab and snatch at material things, to see them only as sources of our satisfaction. Fasting helps us to hunger for God. Fasting reminds us that man does not live by bread alone but by every word that comes from the mouth of God.
“Fasting is an indispensable means of gaining the fruit of the Holy Spirit in one’s life.” — St Seraphim
When a priest complained to St. John Vianney about his parishoners, the saint asked, “Have you fasted for them?”
Prodigal Catholic 
This is so helpful! The Church Fathers know best!!