How the Body Switches Over
When you eliminate carbohydrates, blood glucose drops. Your body doesn't lose energy—it switches from carbohydrate metabolism to fat burning. The liver begins burning fat directly and produces ketones.
"When there is a lack of carbohydrates, and consequently a lack of glucose in the blood, the body switches to burning fat. The liver produces ketones from this fat, which feed the brain directly."
Ketones: Fuel for the Brain
The brain cannot use fat directly, but ketones are pure, exclusive fuel designed specifically for it. They provide the brain with energy of an entirely different quality than glucose.