My wife mentioned something interesting. In the past, when I have dieted, she would comment that my breath would have a distinctive smell–not exactly unpleasant, but “sharp”. I always assumed that was from ketones, produced from fat metabolism.
She has mentioned that right now, I have much the same smell, except much stronger. It doesn’t seem to have anything to do with oral hygiene, so I am assuming it is arising from the unusually high amount of fat metabolism and extremely low carbohydrate intake (less than 15g/day) producing a state of ketosis. I don’t thin k there’s anything I can really do about it other than apologize and try not to breathe on her.
Research suggests that others have encountered similar things.