A water fast is not gonna fix your autoimmune or digestive issue!
Every that I have helped with an autoimmune or digestive issue have had an underlying parasitic infection. A parasite is something that lives and thrives of the host, to the host’s detriment.
So by definition, that could be a (a) Yeast Infection; (b) Worm Infection; (c) Fungal Overgrowth; & (d) Viral Infection
The issue with fasting to resolve this is that these parasitic infections just go into hibernation. Then, as soon as you start eating food again after your water fast, they come out of hibernation and start creating all your problems again.
What we need to do is totally remove these parasitic infections out of your body. So, your body can get back into balance.
You can do all of that whilst having a balanced diet without starving yourself.