VK I too am starting a 72 hour fast tomorrow. Heading out to nature on sabbatical to commune with nature. No TV no computer no phone just me in a cabin fasting, meditating, reading my Bible and being.

I have been doing (2) 24 hour fasts per week for the last 3 years. It has become a lifestyle change for me.
The only thing I consume is water, tea, and black coffee. There are so many health benefits to fasting but too many to go over in this reply. The hardest part is defeating your mind when it is telling you you are hungry. Headaches are possible but when a headache starts to come on or your stomach is growling, dring 8 ounces of water. It will pass. When fasting, it is very important to drink LOTS of water. This washes toxins from your body and out of your organs and you do not become toxic.
Good Luck VK. I am looking forward to hearing how you did.