Certainly true for someone eating well and when talking about 1 meal in many , problems arise for continuous response to insulin a la diabetes a growing problem.
I dont think anyone is worrying about a single meal jzpowahz , very few people would eat clean all the time.
Back to the OP though fasting has been shown to have positive effects , problems would only arise for people who reward themselves with a treat just because they have fasted instead of building upon on the result for a better result as StrungOut suggested.