I'm not the parent commenter, but I feel the same way. Just because something is a fact (although arguably fat doesn't sound very factual) doesn't mean it needs to be discussed during an interview. If someone started Quizzing me on the chemistry of rubber tires for a software dev role, I'd walk too. If someone started listing off the various kinds of sausage there are, I'd walk too. It would make me feel like I'm not taken seriously at best, or that I'm being scammed at worst.

Beyond that, if I looked east Asian, I could also see myself walking on this question for another reason. It would feel like a comment on my ethnic background, which has no place in an interview.

In American culture it's considered rude and gossipy.

Unless I knew what the reason was for asking, it would be like if an interviewer suddenly talked about how much weight Adele was gaining.

Personally, I won't work with paranoid people.