A lot of overweight people do not like the use of the word "fat" because it has become so pejorative. Many people have had it used against them as an insult throughout their lives and it is often part of name-calling ("fatty", "fatso", etc.). Of course, I also have had this reluctance throughout my life to use this word.
A while ago, however, I realized that "fat" is not a dirty word. If your intent is not to insult, it's just descriptive or a noun which is used to describe nutrition or the composition of something. Fat consumption is actually an essential part of people's diets and it is important for good health. It's also a generic word for things like olive oil, butter, etc. It's also a way of describing a body, but that doesn't make it a taboo word. Unlike "ugly", "fat" is not a subjective adjective. "Fat" is a word akin to "asymmetrical" in discussing appearance. Asymmetrical features are seen as unattractive, but that doesn't mean that saying someone's face is asymmetrical is the same as saying they are ugly. Saying you are "fat" does not mean you are ugly, though some people may subjectively reach such a conclusion.
I'm not looking to "take back" the word "fat" and turn it around or anything. I'm only trying to overcome the sting that the word has acquired due to its use as a weapon against people who are overweight. I'm not afraid to say I'm fat nor am I afraid to use the word when I talk. Yes, I'm fat. This is an objective reality, not a subjective observation. If people use this word to hurt me, it is quite another thing from the way in which I use it, and that is to be factual and direct rather than resort to comfortable euphemisms.