Final answer:
The fasted state is a metabolic state in which the body switches to alternative fuel sources, such as fatty acids and proteins. The liver regulates glucose levels by releasing glucagon, and ketone bodies are produced as a fuel source during fasting.
Step-by-step explanation:
The fasted state is a metabolic state in which the body switches from using glucose as its primary fuel source to alternative fuels, such as fatty acids and proteins. During fasting, the body uses stored glycogen and then starts breaking down fats and proteins to provide energy. The liver plays a crucial role in regulating glucose levels by releasing glucagon, which stimulates glycogen breakdown. Once glycogen stores are depleted, ketone bodies are produced from fats and serve as the preferred fuel source for the heart and other organs while the brain continues to use glucose.