Well, as I’ve said a thousand times already, you can only burn calories when you’re on a calorie-deficit.
However, when you fast, you produce more testosterone, more growth hormone, more glucagon, more adiponectin, and become more insulin-sensitive!
…OH YEAH, YOU ALSO PRODUCE KETONES…
which, in addition to the aforementioned factors, help to boost fat-loss whilst maximising muscle-preservation.