Is a fat person really fat?

It depends on your point of view. Lets say there are 3 people

the thin

the average

and the fat

the thin person would view the average & fat person obese

the average person would view people heavier then he/she is as fat

and the fat would view itself and people higher as fat.

It really depends a point of view. Typically when people say

"Oh she is extremely fat!" it typically means very obese in everyones view

But if a thin person is talking to an average person and says

" Oh she is extremely fat!" the average might assume its an obese person while the thin will view it as an average or an obese