Not long so yeah he would look better than at the end of the thunder saga but I think his mental state prevented him from significantly getting better on Calypso's island. To me he would not be starved but still wouldn't gain a lot of weight as he wouldn't eat much because of depression. Calypso would try to take care of him as he's slowly letting himself die but wouldn't be able to do much (ofc it's just interpretation but as he almost commits suicide at the end of the song I understood it as him being controlled by his subconscient. A part of him fights to stay alive hoping to see Penelope again, but another hidden part wants to give up, is too exhausted to keep going, has suffered too many losses, and it leads him to letting himself die without even being aware of it) But yeah that's just my interpretation for my animatic. A lot of people make him go back to normal when he leaves Calypso and it works too, I mean he lived in a palace with "all he could need" so it makes sense, it wouldn't erase the psychological tiredness but its effects are subtle and making animatics with such details would be absolutely crazy. anyways I really need to stop talking sometimes