He's hungry, let the poor man be. Probably didn't eat anything decent since... splitting from the crew? Nah.
Also, I totally had the same theory as VanBuren. On a slightly more serious note: How can he be not Luffy's dad? Garb definitely got something mixed up there...
Poor Sanji... (though, I guess I understand him) and alas, poor Kuma. Honestly, I don't think he'll be back. Just hope they'll make it quick and painless when they face him.