He doesn't change course, hands in his trouser pockets. He killed a boy's hopes and dreams today. In the face of that, he hasn't much of an appetite.

He's never said he's not a bit of a hypocrite, where proper care of oneself is concerned. If the Captain was telling him the same things, he'd still be forcing Jim to eat something.

CMO's prerogative. At least, that's what he's calling it.