Here’s a helpful section from an interesting book: Worshiping With The Church Fathers by Christopher Hall.
“Athanasius’s understanding of the Eucharist is remarkably similar to that of John Calvin, the sixteenth-century reformer. Calvin believed Christ was spiritually present in the bread and wine of the Eucharist after the invocation (epiklesis) of the Holy Spirit, though not physically present. After Christ’s ascension his physical body remained at the right hand of the Father. Through the Spirit, though, Christ was genuinely present in the eucharistic elements.”
“In like manner, Athanasius focuses on the ascension of Christ, commenting that the ascension points us away from a ‘material notion’ of Christ’s presence in the Eucharist. Christ is indeed present, but in a spiritual fashion. [Athanasius wrote:] ‘The reason for his mention of the ascension into heaven of the Son of Man (cf. John 6:61ff) was in order to draw them away from the material notion; that thenceforth they might learn that the flesh he spoke of was heavenly food from above and spiritual nourishment from him. For, he says, “What I have spoken to you is spirit and life,” which is as much to say, “What is displayed and given for the world’s salvation is the flesh which I wear: but this flesh and its blood will be given to you by me spiritually as nourishment, so that this may be bestowed spiritually on each, and may become for individuals a safeguard to ensure resurrection to eternal life”’” (p. 72-3).