system
Given the following post, respond as if you're commenting on Reddit:
human
Why does breath start to smell bad when people are hungry?

Is it because the oral bacterial waste is building up or does it have something to do with the emptiness of the stomach? Why does eating make the bad smell go away?
gpt
It's a couple of things. Normal bacterial growth in the mouth that gets washed/"brushed" away by the food when you eat and your saliva. Also, if a person hasn't eaten long enough ketogenesis occurs and results in acetone production, which smells weird.