The term "more fatness" can be replaced with several antonyms depending on the context of the sentence. If we are referring to a person's weight, the antonyms would be "thinness," "slenderness," or "skinniness." If we are discussing food, the antonyms would be "lean," "skinny," or "low-fat." In biology, the antonyms could be "muscularity," "athleticism," or "fitness." Finally, in fashion or style, the antonyms could be "body contouring," "tailoring," or "streamlining." It is essential to use the correct antonym according to the sentence's context to avoid misunderstandings or confusion.