Well I have a few ideas. You can use none or all doesn't really matter. Just a few suggestions to look at. But over all it's a really neat bust of a fat guy.
-He needs a upper eye lid. As it is now it blends/almost fades into the eye brow fat.
So when you make the upper eye lid more prominent you can then add a bit of eye fat over the top of it like hanging fat.
Also maybe adding some puffiness to the bottom lid might add for a fatter effect.
-At the ? I don't know whats going on it like it was pinched but his face is in a relaxed pose.
-His check bone seems to far in for the shape of his skull. Which would mean his upper lip would need to be a little wider and not so thin in that spot.
Also he could use some facial hair pores might look neat but it's a toss up because he's not really fat but has some fatness to his face.
So skin pores and stuff that that wouldn't show up that much but since it's a bit thinner it would look alright.
-Also his shoulder/neck base would be a little bigger to give off that fatter look.
