Lori -
Right, exactly, it's all about the style of juice fast you do. If all you do is drink pineapple juice all day, that's not healthy.
I definitely recommend the video Fat, Sick, and Nearly Dead for people who want to understand better what a healthy juice fast style is about.
The key is to be comfortably full - but not overfull. The stomach is a flexible organ. It expands if you keep stuffing it - and then it takes more to feel full. I've, over time, reduced the size of my stomach so now it gets full before I can even finish my morning shake. So less than a shake container fills it up. Which is great because I feel happy and full with relatively few calories / carbs in me.
It definitely can be done, little by little, over time.
It's also better for your digestive health.
I would start with one day and in terms of how much to drink, drink until you're comfortably full. Don't worry about "finishing the shake". And drink ample water.
