Your (RMR) Resting metabolic rate is very important, that's the baseiline calories your body needs to consume daily just to run & maintain the bodies organs, systems & basic functions including your brain. (RMR) is different for everyone.
The body has a great way of protecting itself, as it has to survive through what it considers "lean times" when you are not feeding it consistently the right amount of nutrients.
What happens is your body will go "catabolic" & start breaking down muscle to use as energy, as muscle is much easier to break down & convert to a fuel source than fat & there is plenty more of it available.
So you will usually release a stress hormone named cortisol, to anyone doing fitness it's comparable to what garlic & wooden stakes are to Vampires.
Theirs no doubt about it cortisol will get to work much more efficiently than any type of "Wile E. Coyote"® type products!
Joking aside when you go catabolic you literally are eating yourself & your body is slowing down & breaking down & what's worse your get better at storing fat because your body is trying to survive instead of thriving.
So think about what you eat when you eat it & what it's going to do for you short term & in the long run.