can't say I'm a fan of juice fasting as that's just fruit sugar. Sure it has nutrients etc, but without the fiber its going to trigger all the hormonal changes to make you body a fat-storing machine. plus you will be starving all the time. I find it easier to not eat at all and get all the benefits of autophagy (which is what you describe - https://en.wikipedia.org/wiki/Autophagy) . But each to their own ;)