How do I not lose weight? I'm already too thin.

I have much experience with juice fasting....like 25 years of doing it yearly. But, this is my first Master Cleanser fast. I have bronchitis, so I thought that this would be a great time to clean it all up. I am already very thin, and this is a great concern. According to the book I am using more maple syrup than the recipe calls for. Is there anyone out there who has figured out a way to fast and not lose weight on this program?

Juice Fasting Program on the Ocean