Earlier quoted context omitted.
You also have to do an awful lot of exercise to burn a substantial amount of calories.
I ran 16 miles this morning, burned over 2000 calories. But I won't lose any weight, I am going to eat those calories right back.
In a thought experiment (where it's possible to know the exact amounts) -- do you think consuming exactly 2k kcal is perfectly even with burning exactly 2k kcal? IE, is there overhead to transform the energy? Does it account for physical/energy waste?