72h for body to change fuel in reality after total glycogen depletion.. electrolytes with no sugar are super helpful during this phase.. drinking ginger tea or green/black tea is also a good practice. Just avoid coffee as it is too stimulating and dehydrating. Your body and mind should feel rejuvenated not miserable. Take care and good luck
Takes me 3 days.
Found a trick though.
I cheat by lifting or any heavy activity, in order to flush any glycogen from my system.
Flips that switch within 24 hours, and I’m now burning stored fat for the remainder ofmy fast :)