Ketosis

Ketosis is a state in metabolism occurring when the liver excessively converts fat into fatty acids and ketone bodies which can be used by the body for energy.
You may read that it is a "dangerous state" for the body, and it does sound abnormal to be "in ketosis." But ketosis merely means that our bodies are using fat for energy.

When people eat less carbohydrate, their bodies turn to fat for energy, so it makes sense that more ketones are generated. Some of those ketones are used for energy; the heart muscle and kidneys, for example, prefer ketones to glucose. But there is one type of ketone molecule, called acetone, that cannot be used and is excreted as waste, mostly in the urine and breath (sometimes causing a distinct breath odor).