However, the more important question (also answered in the article and the video) is:
Why do people eat more than they need? Why, when the human body can detect when it has enough nutrients and signal satiety to the brain?
The answer being: Because we've developed foods (by using high fructose amounts in them, through sugar) that block those signal paths. We've perfected foods that we want to crave and that don't make us feel we've had enough, so that we can consume more.
Yes, one possible answer to the caloric equation is: Have a strong will, be hungry and you'll be lean. The other is: Eat right, and you'll feel satiated after eating exactly the amount that's needed for your health.
And, btw, the equation assumes that all you eat and is digestible gets digested. That obviously isn't true, when overeating a lot of the food just goes through without the nutrients getting extracted. If that wasn't the case, many people would weigh thousands of pounds today.