While this may sound reasonable, I argue that this advice is completely USELESS. Knowing the First Law of Thermodynamics helps you with weight loss about as much as knowing the Theory of Gravity helps you with flying. Of course, our bodies must obey the Laws of Thermodynamics, but eating less does not help you lose fat. Just like eating more does not mean you will necessarily gain fat. After all, eating more may mean a gain in muscle, bones, tissue, fat, or a combination. When you were a kid, you were certainly consuming more calories than you burned in order to grow. Those excess calories did not all turn into fat! How do people reconcile the calories-in calories-out mantra with everyday phenomena like growing up?
Similarly, a shortage of calories will not necessarily result in burning fat. It may result in metabolizing sugars, muscle, or even your organs in order to meet the bodyEUR(TM)s energy requirements. Plus, over 90% of the calories you burn go into basic metabolic functions. Running for three miles may only increase your calorie burning by an additional 10%. ThatEUR(TM)s not much reward for all that effort. Meanwhile, if you put your body in a caloric deficit, your metabolism could slow down, and you could end up burning fewer calories than you did originally!
This reason explains why most people will see weight loss for only the first two weeks or so. The bodyEUR(TM)s metabolism eventually adapts to the current calorie consumption, and no additional weight loss is achieved without a further decrease in daily food consumption. Sometimes, people end up on these starvation diets just to see the scale go down. Meanwhile, your body is metabolizing your muscles quickly just to keep you alive. The body will hold onto the fat tissue as much as possible on low-calorie diets. Fat is a good repository of energy, and as far as your body knows, it is going to need that stored energy in order to help you live through this mock famine.
So - Is dieting an energy balance? Technically, yes. Your body must adhere to the Laws of Thermodynamics; there is no way to bypass science. BUT this balance is not as simple as you first imagined. In order to master actual weight loss, you must learn to regulate your metabolism the correct way.