Ketones are the “leftovers” eliminated from the body when it uses stored fat for fuel. Ketosis is the state where the body is burning fat instead of glucose.
Since the goal of any weight loss diet is to reduce fat levels, it is a “good thing” to burn fat.
On a high carbohydrate diet, the body converts the carbohydrates into glucose and uses the glucose for fuel; anything not needed is stored as fat.
A low carbohydrate diet forces the body to burn fat, since there is no supply to convert to glucose. The excess ketones are secreted in the urine and in the breath. Ketones in the breath are one of the things that cause “bad breath,” but good oral hygiene can take care of this.
Despite fears to the contrary, ketosis induced by a low carbohydrate diet is not dangerous; ketones do not build up in a healthy body but are excreted. The only exception is in Type I diabetes; when a person cannot produce insulin and his or her blood sugar is out of control, a condition known as ketoacidosis can result.
For the rest of us, though, “ketoning” is simply proof that our body is using the fat we’ve stored – the very thing we’re hoping to accomplish.