grueso vs gordo - uses & similarities
After reading the posts for Chris' Word of the Day "grueso", I began to wonder what the differences are between "grueso" and "gordo". So, first I looked in the dictionary here.... That was helpful... I'm getting the impression that maybe "grueso" isn't commonly used to describe a person as being fat... correct? Or is it a matter of location, as to which word is used? Would someone tell me what the subtle differences are in the use of these words?
2 Answers
I gonna talk about the meaning in Spain, I unknown if in other coutries or regions could have another connotation.
I think "gordo" refered to people could be derogatory so it uses in colloquial conversations or when someone talk about himself. Estoy gordo!, mañana me pongo a dieta! 
And "grueso" in this context could be considered an euphemism, used in conversations more formals. For example: Disculpe, detrás de quién me pongo? Sitúese detrás del hombre grueso de la derecha....
I hope to have helped you! 
I'm reading a series of books where one of the protagonists is a "chubby" [rechoncho] adolescent. I have read where he is described as grueso many times. He is also supposed to be the "brains" of the team, so I do not think that he is being called "thick" [torpe] referring to his intellect.
Googling I see grueso being used as "gordo" referring to people.
What I googled was muchacho grueso and it is interesting to note that google translated it as fat boy.
