Whether on LC or fasting, the answer to low energy is often more water and salt (super important to hydrate on IF) or more fat. Like WearBear the morning with a 7 am aerobics class, I add coconut oil. A true fast is nothing but water, but unless you are doing it for cancer treatment or spiritual reasons, coffee, tea, broth with salt, and even small amounts of pure fat, are allowed on Dr Fung's protocol. Not a 700 cal. BPC, but a tsp. of oil if you feel hungry or not enough energy.