I started outlining and writing a piece about the biochemistry behind it, but (1) it took me down a way deep rabbit hole, and (2) I'm not very clear that I don't understand the topic well enough to write about it.
That said, when doing a basic intermittent fasting protocol a la Leangains.com, it's been relatively easy to consistently march down towards lower bodyfat and greater health and wellness.
I ran a caloric deficit of between 500 and 1000 calories each day, eat all those calories spaced into a 4-6 hour window.
That was pretty good, and remains pretty good.
I've recently (six weeks ago) started experimenting with fasting 24+ hours, sometimes to the 60 to 70 hour range once a week.