1) Have the bodyfat stored as energy if you're going to do an extended fast. I wouldn't push anything beyond a week if you're below 10% bodyfat for men, 15% for

1) Have the bodyfat stored as energy if you're going to do an extended fast. I wouldn't push anything beyond a week if you're below 10% bodyfat for men, 15% for women. 2) Drink water, not too much, not too little. 3) Supplement electrolytes. Sodium, Magnesium, Potassium. You can see my comments elsewhere in this thread for more details on that.