Although technically true, it's much easier (and quicker) to gain X calories than to lose them via exercise. So if you're overweight, your number one priority is to control your diet. Regular exercise is important for health reasons, but not to lose weight.
There are exceptions. If you're a professional cyclist, for example, and able to output several hundreds of Watt for several hours, 6 days a week, you'll quickly lose weight through exercise. But that's not actionable advice for regular people with a full-time job and a family.
If only thing you will do is to control calories, you are pretty much guaranteed to get into the yoyo cycle of loosing/gaining weight. Majority, like almost all, people who only focus on calories stop performing in their lives, becomes tired/sick, give up and gain weight.
If you are overweight, if your concern is not purely temporary esthetic, focusing on calories control is receipt for long term failure.
Also, the exercise is not done only so that you immediately spend some calories. It is to build muscle, raise temperature, speed up your metabolism. All these affects you calorie consumption long term.
High level competitive sport has nothing to do anything. It has zero to do with what average adult experiences.
Yes, that's great, exercise is important for your health, I already mentioned that. Doesn't change the fact that you generally won't lose weight through exercise, but through a change in diet.
> It is to build muscle, raise temperature, speed up your metabolism.
Those effects are negligible compared to eating, say, 20% less. In particular because exercise makes you hungry, and if you don't control your diet, you'll regain the lost energy through increased appetite afterwards. So again, yes, please exercise regularly, but that alone won't make you lose weight.
> High level competitive sport has nothing to do anything. It has zero to do with what average adult experiences.
Uh, yeah, that's exactly what I wrote: professional athletes are an exception, and their case doesn't apply to regular people.
There are exceptions. If you're a professional cyclist, for example, and able to output several hundreds of Watt for several hours, 6 days a week, you'll quickly lose weight through exercise. But that's not actionable advice for regular people with a full-time job and a family.