Many people report feeling older injuries/illnesses during prolonged fasting. It's not clear what is the nature of that, if it's just psychosomatic and some neural pathway is correcting/readjusting/"backpropagating" itself (think phantom pain) or if the original repair was "temporary" and body does a proper rebuild there, or something completely different is going on. Try 1 week then tell us if you felt something similar, I did.

EDIT: This Reddit thread has interesting comments, elevated HGH might be the culprit:

https://old.reddit.com/r/fasting/comments/5gl1aq/can_fasting...