This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lipids, Subject name: Biochemistry
The major fuel in the brain after several weeks of starvation is: 
Select and explain. 
A. Glucose, B. Fatty acid, C. b-Hydroxybutyrate, D. Glycerol
C: b-Hydroxybutyrate
Answer: C: b-Hydroxybutyrate 
Explanation: Ans. C. b-Hydroxybutyrate(Ref: Harper 31/e page 210)In the prolonged fasting stage, 20% of brains energy is met by ketone bodies. Rest by available glucose. But after several weeks of starvation, ketone bodies provide the major metabolic fuel.