Avoid Muscle Loss during a Juice Fast - How?

As the title says, I've been wondering how to avoid Muscle Loss. I'm on Day 6 of 40 on my Pineapple Juice Fast, I'm an athlete so this is a HUGE concern to me. I want to avoid losing Muscle during the fast, if that's possible.

I'm close to my idea weight, with maybe only 10-15 pounds MAX to lose, but I'm getting concerned because my Ribcage is starting to show and I don't want that. I just wanna be muscular (relative to my sport) and don't want to look emaciated. My fast is as much for Health improvement as it is for the remaining 10-15 pounds I've never been able to lose, but more geared towards my health than anything.

I wonder how your body deals with lack of Protein and Carbs during a long juice fast like this. How does it feed and maintain themselves without both?

Thanks in advance!

Cyane Tweet