From the article-
"The term obesity comes from the Latin word obesus, which roughly translated means intensive eating"
In that context, Obese is a much more brutal word than fat.
I always thought of the degrees of fatness this way.... someone eats too much- they become a bit overweight. They keep getting bigger until they are chubby. then they keep eating till they get fat. Then they keep it up and they become obese. Then they cannot move anymore, keep eating and become morbidly obese.
Obese is always the last step before Gilbert Grapes' mom.