Rome says the host is REALLY Christ's flesh.
However; in the favorite book of Catholics; Christ Himself said:
The Spirit gives life; the flesh counts for nothing. The words I have spoken to you-they are full of the Spirit and life.John 6:63
But it REALLY does not look like the Lord's body which was broken, and His blood which was shed, with its manifest physicality that John emphasized, versus a Gnostic or Docetist Christ who was not what He appeared to be. And which soon to be crucified manifest flesh and blood a straight-forward literal reading of the "words of consecration" would refer to. Nor is there anything in the text which requires this to still look like bread and wine.
But since Cath priests cannot change the bead and wine into the manifestly incarnated flesh and blood of Christ (aside from a few purported miracles which do not conform to Eucharistic theology), then while what Caths receive REALLY looks like bread and wine, they are to believe that it REALLY is the crucified body and blood of Christ (even in the smallest particle), while the bread and wine REALLY no longer exist, Christ being present instead.
That is, until the bread and wine which no longer exist REALLY exist begin to manifest decay, at which point the Catholic christ REALLY no longer exist under that appearance. Nor does the bread and wine either according to Aquinas. At which point as concerns the "Real Presence" in that locale, theologically
they have taken away my Lord, and I know not where they have laid him. (John 20:13)