I'm looking at those pictures, and I haven't seen a what I'd call a truly fat person yet.

As some have been saying here, and I usually hear it most from ladies and gentlemen of the south, I feel a more apt term is stout.

To me, the kilts I have seen look to be fitted well, and the wearer's look comfortable.
BTW, this comes from someone who used to be called "Fat Matt the River Rat"