I’m not sure if I asked this quesasssion in the title properly but I read somewhere that you burn the most fat once you hit 10 days in? I was planning to do a 4 day this time around but I’d like to maximize my fat burn if possible so if I need to do 10 days (which I have done before) I will. Any thoughts?
That doesn’t make any sense to me. After you hit ketosis, you are using fat as a primary fuel and thus you are burning approximately your BMR + active kcal of fat each day. Fasting for longer won’t increase the calories you spend (matter of fact, it might decrease since some people feel sluggish, cold, etc).
After your liver is empty of glycogen, you will be burning all fat. This takes 48hrs for women, and 72 hrs for men. It’s a mix before hand. My ketones usually starts near 0.0 and head pretty linearly to 1.3 (at 72 hrs) and then bam 2.3 or above right after.
So, very roughly, after 3 days you are burning near all fat.