Does what we eat affect us spiritually?
I would answer yes. If we are full, if we have eaten many desserts and in general a big meal, it is more difficult to pray. To progress in prayer and in general to progress spiritually we need above all to be humble and to love, we need faith, but also self-discipline and ascesis helps. I feel that what you are asking about is fasting. If someone has significant medical problems or other hardships, then their spiritual father may advise them not to fast, or to fast in a modified way. Most of us, however, are encouraged by the Church to fast.
This means that we do not eat certain foods on Wednesdays and Fridays, on Wednesday because of the unlawful council against Jesus and the betrayal of Judas on that day; and Friday is the day Jesus suffered and died on the Cross. There are also periods of the Church year that we are called upon to fast: before the great feasts of Pascha, Christmas, the Dormition of Panagia, and the feast of the Apostles. There are also the single-day fasts: on the Feast of the Exaltation of the Holy Cross, on the eve of Epiphany, and on the day commemorating the Beheading of St John the Baptist.
When we fast we abstain from certain foods: this varies somewhat, but often consists of not having meat, dairy products, eggs, fish and on very strict fasts even oil. On fasting days we also try to not eat as much, to finish our meal a little before we are full. Fasting is beneficial spiritually. Of course it can become even more beneficial if during fasting periods, as well as avoiding certain foods, we try extra hard to be spiritual.
In other words to put extra effort into prayer, reading of the Scriptures and spiritual books, being attentive during Church services, participating in the Sacraments, striving to do works of love, to bring others to Christ, to forgive, to be humble and patient. The Sticheron at Vespers on Wednesday of the First Week of Lent is as follows: “While fasting physically, brethren, let us also fast spiritually. Let us loose every knot of iniquity; let us tear up every unrighteous bond; let us distribute bread to the hungry, and welcome into our homes those who have no roof over their heads”. Fasting does affect us spiritually, and does help us.
Fasting is a type of rebellion, a refusal to accept that I am just a body, and that the needs of my body are the only part of me. Fasting forces us to remind ourselves that there are higher aspects to our nature than just our bodily needs. Fasting is a spiritual discipline. As Fr Alexander Schmemann wrote in his book Great Lent: “the purpose of fasting is to liberate man from the unlawful tyranny of the flesh, of that surrender of the spirit to the body and its appetites which is the tragic result of sin and the original fall of man. It is only by slow and patient effort that man discovers that he ‘does not live by bread alone’ – that he restores in himself the primacy of the spirit”.
In terms of how we see people around us who are not fasting, we need prudence. St John of Damascus put is as follows: “It is good to fast, but may the one who fasts not blame the one who does not fast. In such matters you must neither legislate, nor use force, nor compel the flock entrusted to you; instead, you must use persuasion, gentleness and a word seasoned with salt”. (On the Holy Fasts, Homily 3). Fasting has been with our Church from the beginning. Jesus Himself fasted for forty days before commencing His public ministry (Luke 4:1-2) and provided instructions on how to practice fasting (Matthew 6:16-18). In the book of Acts we learn that in the early Church they would fast, particularly prior to some great and holy work: “So when they had appointed elders in every church, and prayed with fasting, they commended them to the Lord in whom they had believed” (Acts 14:23).
Source: Lychnos October / November 2016