That used to happen a lot for me a few years ago, but it still happens occasionally. For me, though, it's always been a symptom of a non-physical, often deeper problem. Like, if I'm nervously stressed out about something over several days, my appetite will tend to suffer. Also, a feeling of sadness/emptiness inside can trigger a loss of appetite for me, too. Be careful, please...Don't go without eating, just because you have no appetite. You need to eat SOMETHING, even if a little bit at a time, to keep your metabolism functioning well.