well, *obviously* i wouldn't recommend lying about fasting just for fun, or lying to a person who is most likely enlightened and/or open-minded. BUT, if you know you're talking to a narrow-minded person who probably wouldn't understand, then why waste your energy? i'd rather not "cast my pearls before swine" and waste valuable resources trying to defend my beliefs to a brick wall.
Who on earth would waste their energy talking to someone narrow minded? If I'm doing something that they don't grasp, that's their issue to deal with - not mine. I may be a lot of things but masochist is not one of them.