Ketone Body

Definition

Ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) are molecules produced by the liver during the breakdown of fatty acids during fasting or severe carbohydrate restriction.

How it works

During prolonged fasting or a ketogenic diet, lipolysis releases fatty acids. The liver converts them into ketone bodies that cross the blood-brain barrier and fuel the brain (up to 70% of its needs). Nutritional ketosis is different from diabetic ketoacidosis, which is much more dangerous.

Role

Fuel the brain and muscles in the absence of glucose, spare muscle proteins.

Examples

• Ketogenic diet (<50g carbohydrates/day)
• Prolonged fasting > 24h
• Untreated type 1 diabetes (ketoacidosis)

Recommendations

Nutritional ketosis is safe for healthy individuals but should be supervised in cases of diabetes.

Key takeaway

The brain can function on ketone bodies — it's an evolutionary adaptation to fasting.

Related terms