Of course your metabolism has no idea what time it is. It doesn’t matter what time it is—after 12 hours of fasting, you have burned through your glycogen stores. It’s literally just biochemistry.

Get off your bro science high horse. You clearly don’t know as much about metabolic processes as you think you do.

I suppose my “hot take” would be that after you’ve fasted for more than 12 hours, you have burned off any glucose plus all of the glycogen stored in your liver. There is no longer any form of carbohydrate to derive energy from, so the body directly mobilizes fat stored inside adipocytes. That produces ketones in the body, which have been shown to have their own beneficial effects.

Eating all day at a calorie deficit will slowly chip away at the fat, but it’s less effective because energy for the missing calories are taken from a constantly-replenished glycogen store, plus some from fat cells. Removing the glycogen store in the liver through fasting and forcing fat cells to provide all of the energy instead, means your calorie deficit is being taken directly from fat stores. Remaining in the glycogen-depleted state for a few hours per day means more fat is burned through for energy in total.

Adding in the fact that excess glycogen stored in the liver is converted into fat and stored in adipocytes, the less glycogen you have overall, the smaller the fat stores in adipocytes will be, and therefore overall weight.