Happy reading about the "fitness system".
i see your game as an open world sandbox with storytelling - it will benefit from all stats going up AND down, so players can tell (or retell) the story they like.
Hope the fitness stats will also work in both directions - so players can transform and shape characters freely. Ofc. all with some effort or lack thereof.Played quite some sandbox, life sim or stat building games, many of them involving food and body stats.
What bothered me was that some of them did only go into one direction. Level up but never down - resulting in a dead ends.
Seems you are on a good path, not only with the above.
regards,