This can be found in John 6.I bet the disciples that walked away did not understand that Jesus was not saying"Here I am,eat me.
I’m not concerned so much as some not understanding that Jesus calls himself at one point in scripture The water that we can drink and never become thirsty again.Here he was speaking of a spiritual water that we can drink freely from.Jesus however did not mean water that you could find on this earth,only through him can we have eternal life.When we eat his flesh and drink his blood,this is like being in Christ and Christ in us.This thing they did was for the Spirit of man,to be be in accordance and in Christ.I’m going to leave it at that because I do not want to confuse you on your search for the Lord.I have an understanding but mine is different because I’m not Catholic,so I might confuse you here in your search.

The bread represents that you are the body of Christ because you ate him(Spiritually)The blood represents that you are washed in his blood and that is how you are part of the body of Christ.I hope I have not confused you with a protestant view