I actually avoid fruit juice in favour of the associated fruit.
Most fruit is classed as a free food by people like Slimmers World and on the Weight Watchers "core"
diet. That is because both these diets are based on the concept of filling foods (GL glycaemic load which is GI gycaemic index on portion size). Both these diets push people towards opting for a healthy alternative and encourage people to eat until they feel satisfied but no more.
The concept is that if you lined up 10 apples and ate them you would feel pretty full. If you juiced them and drank that you would not feel nearly so full and would have consumed the same amount of
calories.
I have never wanted to do a fast. I would just punish myself and am convinced that I would feel no gain.
The only time that I have not eaten for three days was when I had an operation and I certainly didnt lose weight that week.