Ah, digestion! The old-school parochial schoolkid’s question! Which pretty much never matters!
Almost as soon as Communion is consumed, the Host becomes unrecognizable as having the appearance of bread, and ditto for His Blood and the appearance of wine. Things get thoroughly diluted, dissolved, and molecularly taken apart. And since it’s unrecognizable, you know that it’s no longer Jesus. Since this is the rule on other Communion stuff (like dropping consecrated Hosts into a pool of water, or similar what-if questions), it also applies to digestion.
(The only time it really matters is if somebody swallows the Host and coughs it back up immediately in a recognizable form. I suppose it might also matter if one had a serious stomach problem; but one could safely ask God to look after Himself, or just receive Communion from the chalice.)
Of course, if you follow one of the old pious customs like “making a thanksgiving for Communion” for five to fifteen minutes in a pew after Mass, you definitely don’t have to worry about this stuff.
But actually, you never have to worry. Jesus Christ was a pretty good eater, and He knows your need to eat. That’s why there’s no rule, and never has been one (AFAIK).
It was the custom for synagogue meals to start immediately after the service, and what little we know about Early Christian Masses shows that they tended to eat meals together right afterward, too.
So break your fast right after Mass (or even right after Communion, if you have serious reasons), and be happy!
(That said… If a person has serious blood sugar problems, candy would constitute medicine. Even in the old days, medicine did not break the fast.
(Also, anyone sick/frail enough to need medicine during Mass is excused from the Communion fast, anyway.
(It’s meritorious to try not to break the fast and try not to scandalize your pew neighbors, but fainting is not good.)