And the reality is that simply taking in fewer calories will often cause your body to burn fewer calories because your body is meant to conserve energy for the times when it is needed to run away from the bigger predators.
Discipline is easier when you aren't hungry it turns out.
The food labels on your food packages are determined by calorimetry. But your body digests some food more readily than other foods, also affected by what else you eat with it, how you prepare it, etc. Also your body encourages you to eat certain things to get various nutrients: you rarely eat those nutrients alone; typically they come along with a bunch of other stuff. Then peoples' feedback systems are heavily influenced by all sorts of things: signals from your gut biome, your emotions and response to social signals and learning, various kinds of signalling reflecting what you eat (and those signals are empirically hacked by food engineers), and random brain bugs, among others.
Exercise is hardly scientifically measurable either. It's not like that "calories burned" reading on your bike, is comparable to a bike from a different manufacturer, much less a different kind of exercise.