How does the human body prevent internal energy levels from becoming too low?

The nervous system transmits feelings of fullness to the digestive system, which signals metabolism to stop.

The digestive system transmits feelings of fullness to the nervous system, which signals metabolism to stop.

The digestive system transmits feelings of hunger to the brain, which initiates eating.

The brain transmits feelings of hunger to the digestive system, which initiates eating.

The brain transmits feelings of hunger to the digestive system, which initiates eating.

The brain transmits feelings of hunger to the digestive system, which initiates eating.