I feel compelled to mention, because I am aware of ignorant doubters, that when I juice fast, my body actually gets supercharged with nutrients and is in a condition to better absorb what it needs, without having to digest anything. So...I am not starving! Juice fasting is a skill and an artform; you don't just quit eating and expect to accomplish anything.
Also, the main difficulty is the mental obcession with eating. Working with this contemplatively is part of the gift of fasting.
I will share my journey; its ups and downs.