The followers listening to Christ could not accept what He was saying, they listened with disdain & disgust.
He foretold His Ascension, indicating the body they ate would be His Resurrected Body. It would be spiritual food, for spiritual life, now and after death.
Christ did not prompt his statement to say this was only a symbolic description, nor did he retreat from his statement. He allowed those who wanted to leave to do so.
As a matter of faith, we face the same dilemma and choice today – lifeless symbol or real presence?
Will you see the Body of Christ shared in the Eucharist as a mere shadow of its real substance or will you choose the path of faith and commitment as Peter did?