If he's gained some weight, he may not have as much appetite just because he's getting more than sufficient calories. I wouldn't worry too much about it unless he starts to lose weight again.
Glad to hear he's feeling feisty!
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."