I fasted while working for 20 days. Its doable.
Look for posts I made on this topic, they include my observations and theories as well.
However Fasting is like jump starting your car, You can do it, and it could get you clean and lose weight etc, But you would need to keep it that way by clean eating and clean every thing else for the rest of your life. That is far more important than just the 1 time jump.