Epinephrine and norepinephrine are both fight or flight hormones, often called adrenalin and noradrenalin. When they are released into the blood stream, they trigger the release of glucose from energy stores, and increase fat burning.
They also make you feel awake and alert. Fasting increases the amounts of both of these hormones in your blood. This is your body’s way of maintaining your blood sugar levels and increasing your fuel supply by helping to release fatty acids from your fat stores.