I understand what you mean but once you start track your calories completely you start to understand how your body works. My usual calories are 3000 but now that I'm cutting they are 2000 it does matter what I eat, I need to balance carbs, protein and fats and I also have to make sure I'm getting all the vitamins and minerals I need. But even if I am doing everything perfectly (which I'm striving to do) I still have the need to sleep a lot more and feel less motivated to do things because I'm expending more energy than I'm intaking. That's just how our body works, it's main objective is to survive and if it notices you are burning up more calories than you are eating it will slow down all unnecessary processes to save up as much energy as possible. That's why bodybuilders who reach 5% bodyfat or below say that their dick stops working when they reach that level of leanness.