I have walked up to people and said "OMG, what are you eating?" regardless of what they're actually eating, and then following up with "Isn't that really annoying, when people make a fuss of your food?"
I hope if I do it loudly enough, people will work out to avoid doing it to me.
I have had at least one person try and change the topic back to me mocking their food, since the actual work topic was unpleasant. Good to know.