If we consider fed and fasted to be the yin and yang of metabolism, then the hormonal equivalent to fed and fasted could be thought of as insulin and glucagon.
Insulin is the dominant hormone in the fed state, which causes you to store food calories in the form of fat and glycogen. Glucagon is one of the dominant hormones in the fasted state that causes fat burning.
Insulin = Fat storage
Glucagon = Fat burning
The primary role of glucagon is to maintain your blood sugar levels while you fast. It does this by shifting the body into ‘burning’ mode.
Glucagon has some amazing effects on the human body, including maintaining our blood sugar levels, increasing fat burning, decreasing the production of cholesterol, and increasing the release of extra fluids from the body.
Because of the typical way we eat, we spend almost all of our time in an ‘insulin dominant’ metabolism (remember insulin = fat storage). By adding fasting into your lifestyle, you allow your body to revert back to a natural balance between an ‘insulin dominant’ metabolism and a ‘glucagon dominant’ metabolism.
Extract from the ebook Eat Stop Eat by Brad Pilon.