Gluconeogenesis is the process of breaking down protein consisting of skin, connective tissue, and lean muscle to make glucose, the primary energy source for our body. This can be very dangerous depending on the length of the fast and the amount of exercise that we do. If you don't give enough time for your body to recover and expend too much energy, you can break down a lot of lean muscle to provide the quick burst of energy for the body so it doesn't shutdown.

For longer fasting periods, it is important that we rest and give the body time to repair itself. Stressful situations like exercise inhibit gluconeogenesis more than doing nothing and we don't want to lose lean muscle, so we need to make rest the main priority.