Fasting is something that has been done since the very beginning of humanity as we know it. Before looking at the purpose of fasting, the very idea of fasting has to be defined. The regular definition of fasting is “going for a certain length of time without eating anything,” as mentioned by several dictionaries. In Christianity, we can use a broader definition of fasting, namely the abstinence of something for a greater purpose. This can mean fasting from the Tree of Knowledge (Genesis 2–3), fasting with the tongue (Joshua 6), fasting from animal-based products (Daniel 6), and more.
The Importance of Fasting
After having defined fasting, the purpose of fasting can be examined in more detail. The importance of fasting is realised in the story of the fall of Adam and Eve. Before the fall, humanity lived driven by the spirit and used the body to obey the spirit. However, after the fall humanity was driven by the body and inhibited by the spirit. Prior to the fall, humanity lived ‘’vertically’’ as their solemn focus was God and living with Him. After the fall, humanity lived ‘’horizontally’’ as in they only focused on the creation and neglected the Creator. This ‘’switch’’ in focus is the one that ought to be targeted during fasting periods. Basil of Caesarea (379 AD) summarises this idea, saying,
‘’Fasting was ordained in Paradise. The first injunction was delivered to Adam: ‘Of the tree of the knowledge of good and evil, you shall not eat.’ ‘You shall not eat’ is a law of fasting and abstinence.” The general argument is rather against excess than in support of ceremonial abstinence. In Paradise, there was no wine, no butchery of beasts, and no eating of flesh. Wine came in after the flood. Noah became drunk because wine was new to him. So fasting is older than drunkenness. Esau was defiled and made his brother’s slave for the sake of a single meal. It was fasting and prayer that gave Samuel to Hannah. Fasting brought forth Samson. Fasting begets prophets and strengthens strong men. Fasting makes lawgivers wise; it’s the soul’s safeguard, the body’s trusty comrade, the armour of the champion, and the training of the athlete’’1.
Why Do We Fast?
During fasting periods, the believer ought to try to live the pre-fall life that we were ordered to live. Note that St. Basil mentions that in paradise there was ‘’no butchery of beasts, no eating of flesh’’. In the garden of Eden, God gave Adam and Eve ‘’every herb that yields seed which is on the face of all the earth, and every tree whose fruit yields seed; to you, it shall be for food’’ (Genesis 1:29); even the animals ate only fruits and vegetables (Genesis 1:30). Even after the fall, God instructed Adam and Eve to hold on to their vegetarian diet (Genesis 3:18–19). Eating animals was only done after the flood, as humanity had reached a very low state. Origen the Scholar (254 AD) summarised this saying:
”Originally, God permitted the use of foods from vegetation, that is, vegetables and the fruits of trees. But the opportunity of eating flesh is given to men later when a covenant was made with Noah after the flood’’2.
This means that we have to fast in two ways, namely: fasting from bodily influences by reducing worldly cares and eating the same food as we did before the fall, as well as fasting with the spirit by increasing our spiritual activities and drawing nearer to God.
Therefore, the purpose of fasting is to restore the ‘’switch’’ that happened with the fall of humanity. By mimicking the life that we ought to have lived, we ascend ourselves to the life with God that humanity was called to live from the very beginning. Gregory of Nyssa (394 AD) said regarding this:
‘’Nature had not yet been divided; everything was completely fresh. Hunters did not capture prey, since people did not yet practice this. The beasts did not yet tear apart prey, since they were not meat eaters yet…. So was the first creation, and to this creation will be restored after this [age]. Humans will return to their original creation, rejecting hostility, a life encumbered with care, and the slavery of the world to daily worries. Once they have renounced all this, they will return to that utopian life which is not enslaved to the passions of the flesh, which is freedom, the closeness to God, a partaker of the life of the angels’’3.
By fasting, the believer regains the life he should have been living. Augustine of Hippo (430 AD) further explained this saying:
‘’Fasting cleanses the soul, raises the mind, subjects one’s flesh to the spirit, renders the heart contrite and humble, scatters the clouds of concupiscence, quenches the fire of lust, and kindles the true light of chastity. Enter again into yourself’’4.
 Basil of Caesarea. Homily on the Holy Spirit
 Origen the Scholar. Homily 1 on Genesis, section 17
 Gregory of Nyssa on Genesis 1:29. Catena Bible & Commentary
 Augustine of Hippo. Sermon on Prayer and Fasting