The spiritual discipline of fasting has been part of religious life since the very beginning.
In Paradise, the Lord commands Adam (Gen. 2:16–17):
From every tree that is in the paradise you may eat for food, but from the tree for knowing good and evil, you will not eat from it. And on whichever day you eat from it, you will surely die.
When Adam broke the fast—eating from that tree before he was mature enough to handle it—the consequence was corruption and death. Through one man’s sin, death entered the world (Rom. 5:12). While some have speculated as to whether or not man was always intended to eventually partake—and be transformed through death and resurrection—what we know for sure is this: Adam was meant to abstain; he was meant to fast. He was meant to say “no” to his own desires, so that he could say “yes” to God.
We don’t fast in order to merit or earn anything from the Lord, but rather to become like him, imitating Christ in his own forty day struggle. And when Christ was tempted by Satan (as all who are engaged in Christian fasting will no doubt experience), his reliance upon both prayer and the promises of God were enough to sustain him.
Of fasting, the Lord taught his disciples:
And when you fast, do not look dismal, like the hypocrites, for they disfigure their faces that their fasting may be seen by men. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by men but by your Father who is in secret; and your Father who sees in secret will reward you. —Matt. 6:16–18
Christ mentions fasting as a foregone conclusion for his disciples. We also see that fasting is useless if it is not done with the right spirit. Those who fast publicly and with great fanfare have received their reward, and it is both temporal and fleeting. True fasting is a spiritual discipline that affects one’s whole person, aiding in one’s transformation into the likeness of Christ.
As the Orthodox Study Bible notes:
Fasting is for spiritual growth and the glory of God, not to be seen by those around us.
The preparation for fasting in the Orthodox Church is seeking forgiveness from one’s fellow parishioners (Forgiveness or Cheesefare Sunday, the last Sunday before Great Lent), along with preparing for the fast gradually so that we are not caught off guard and more likely to falter.
Alongside fasting from food, one must also fast from the passions. Otherwise, our fasting is truly in vain. On the eve of Great Lent, we sing:
Let us abstain from passions as we abstain from food.
And St. John Chrysostom likewise warns:
What good is it if we abstain from eating birds and fish, but bite and devour our brothers?
When the apostle tells the Romans, “put on the Lord Jesus Christ, and make no provision for the flesh, to gratify its desires” (Rom. 13:14), the emphasis is not the rules of fasting, but rather the transformation of one’s soul and body—transformation into a true and complete likeness of God.
The apostle also tells the Galatians (Gal. 5:16–17):
[W]alk by the Spirit, and do not gratify the desires of the flesh. For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh; for these are opposed to each other, to prevent you from doing what you would.
He shows us again that we are at war with our own desires (the desires or lust of the flesh). In order for spiritual renewal, one must strive to place the importance of that which is eternal over the temporal desires that tempt us, and which Satan and his demons use to lead us astray.
The purpose of fasting is not mere dieting or carnal in nature, but rather gets to the heart of what it means to be truly human. Our relationship with the Father was distorted in Paradise, and only through true spiritual renewal—such as can be experienced through the ascetic discipline of fasting, coupled with both prayer and almsgiving—can we grow to become greater than the sum of our parts. Through this, the first Adam becomes the last and true Adam.
This is why fasting is an integral part of the Christian life, both taught and encouraged by the Lord himself. But we must always do so with a right heart, in the right way, and for the right purpose.