Place it immediately after the teasing line in an edit, as the direct comeback, then follow it with No No Wait Wait for a panicked backtrack before the group reacts. For a bigger payoff, close with Oh My God Wow after the denial, letting the second reaction sell the joke.
About this sound
This clip is a short Dutch spoken line, lasting just over five seconds, in which a voice insists, in Dutch, that the speaker is not fat at all. The delivery is blunt and defensive, turning a simple denial into something stubborn and a little overdone. It feels funny because the protest sounds too forceful for such a small claim, like someone caught mid-snack and refusing to admit it.