The Art of "Fasting"

On Thursday at my internship, we were all having lunch together when I noticed that one of the Indian women I work with was only eating potato chips.  I made a comment about her healthy meal (jokingly of course) and was matter-of-factly told that she was fasting because it was Thursday.  Apparently Thursday is the day of the God her family worships.  Okay, that part makes sense but why is she eating potato chips if she's fasting? They started laughing.  They explained that everyone fasts differently and in some traditions, you are allowed to eat any form of potato when you fast.  I'm not joking.  You can "fast" and eat any form of potato you want, including potato chips as long as there is no extra flavoring on them.  Salt is okay though.  Some things I will never understand.