Watch this video
Fat, Sick & Nearly Dead
"100 pounds overweight, loaded up on steroids and suffering from a debilitating autoimmune disease, Joe Cross is at the end of his rope and the end of his hope."
http://vimeo.com/40023282
Depends alot on your health and your weight.
The guy in the video had lots of fat to use as energy.
Go for vegetable juice over fruit, more nutrients and less sugar
I think the reason it works is because you are not consuming -
Grains, Sugar, Vegetable oils