system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Fatty acids are the main source of energy for
assistant
The correct answer is  Fed state Preferred fuel
Starvation preferred fuel




RBC


Glucose
Glucose




Heart


Fatty acids
Ketone bodies




Brain


Glucose
Ketone bodies




Liver


Glucose
Fatty acids / protein




Muscle


Glucose
Fatty acids




Adipose tissue


Glucose 
Fatty acids.