Well what makes one "fat"? is it actually fat under the skin? 
I would rather be called fat than huge or obese.
I have always been of the thought process that if you didn't like something then change it. If you don't like being noted as fat then lose some weight. 
I've never been sure myself, madam.
I'm altitudinally-oriented, not width-oriented.
In other words, I notice the height of an individual long before I notice the girth.
Sometimes I never get around to noticing the girth at all.
And then in perceiving people in real life, I discount some things.
If a woman's borne infants, for example, I substantially subtract from my perception of her weight, because bearing infants is hard, arduous work and sometimes it's not easy to recover from it. So, for example, a woman might weigh 235 pounds, but if I've discerned that she's borne infants, my brain and my eyes see a 115 pound woman instead.
Or if I see a guy who weighs 400 pounds, but he's working away shoveling grain or something, my brain and my eyes see a 200 pound guy instead.
I dunno why I do this; I suspect it's because I'm trying to look at the soul of a person, rather than the body.
My descriptions of people in real life are usually in variance with descriptions of the same people by other people. (Size only; other details such as hair, skin, eyes, male, female, approximate age, whatnot, there's agreement. Size only.)