I've read, and also heard, that if you drink only 100% pure juice along with fruits/vegetables for 24-36 hours, then it will not only detox your body, but also cause you to lose weight. Does anybody know if this is true?

True to a point! What no one mentions is that once you add food back into your diet you'll gain that weight back immediately! There's a web page below that talks about cleansing diets and the pros and cons...