I'm currently on the third week of my juice fast. Honestly I'm not sure if it's the fast or if it's the fact that I'm sleeping better then I ever have in a LONG time but I HAVE AN IMMENSE AMOUNT OF ENERGY! I've been working out and just "going" throughout the day. Anyway, at first you will be very tired and maybe even weak but stick it out and you'll find you will have more than enough energy for all of your activities!