Some people said that fasting or meal skipping is one reason of having a bad breath. I'm doing OMAD for almost 2years now. My breath is okay and I haven't receive any bad comment about it so far. I remember reading an article before it said that if our stomach is empty our intestine is not digesting any food it releases some sort of chemical. Sorry, I'm not good in science so I bearly remember it, it's something like that. So that gas or chemical causes the bad breath in short. Try at least, eat some thing or anything. Just try it. Or the best way is consult your physician.