Do We Have This One?
Quickly, try to think of a king that isn't tremendously fat.
You probably didn't think of any, or King Triton from The Little Mermaid
. This is because many kings are corpulent.
Kings are on occasion depicted as morbidly obese, fat lards because they're usually thought to be just sitting on their throne, warming it while doing nothing.
Can sometimes, but very rarely, apply to Queens. (But queens aren't really that common in media as much as Kings.)
This trope is completely non-existant in Real Life
. Almost every king and queen are trim and fit.