As far i seen, all infections comes from skin status and immunity. Low immunity and skin durability, infection on 30% is on (cuz usually i take notice that spawns on that). Much pain status on exact part might effect on character.
On add, you can overfed and make character fat (but I am sure that chubby is a effect. Fed a lot fat things (chunk of meat, hamburger)).
And too say, I am not sure of all, but I can say that what I observed so far. So take all with some grand of salt (or what was say).