There is a specific moment near the end of an illness when food sounds appealing again. Nothing else has changed — still weak, still in the clothes you have been in for days — but you want toast, and yesterday you did not.
That is the turn. It arrives before you feel well, and it is the most reliable signal going.
Vitality returns in that order: appetite, then interest, then energy, then the sense of being yourself again. Wait to feel fully restored before believing you are on the mend and you will miss the first three.