One of the weirdest things about emerging from switching from an outside in caricature of fatness, to an inside out experience of self, is how often I find my assumption that I knew what people were talking at me, dashed.
Take the above. It means, the calories the you put into your body must equal the calories that are spent by your body.
That means, if you consume 2,000 calories you must use 2,000 calories.
Okay. When you take calories into your body, your body uses them in functioning at all, including eating and processing what you've eaten so you can use it, or digestion. It also uses energy to hold or store them too, expending energy to keep them.
If it means calories in equals calories out, literally, then lowering calories, will lower expenditure of calories, resulting in equilibrium, of that lowered energy.
If you take in less calories and increase expenditure say through exercise, you will use less energy for everything else to allow for this increased expenditure.
To say that all energy must be accounted for, is not the same as saying if you eat less, your body will use the same amount of calories it did when you ate more calories.
If you eat less, you expend less, if you eat less, and raise your calorie expenditure, you will expend less in other areas.
The issue is, why is your body storing calories, what for?