Let me start by saying i am a total newbie to fasting, but im keen to try it.
Two of the guys in my office seem to have some insight, although very different stances on the science.
First guy says intermittent fasting (he does 6hr window 5 days a week) works because you always eat below maintenance calories on fasting day. Simply because you cant consume that much food within the limited eating window…
Second guy claims you can you eat your normal amount of maintenance calories (or slightly over) and can still lose weight because during the 18hr fast, your merabolism is faster. So your true “maintenance” is probably ~1000 caloroes higher than normal.

Which of them is right?