That is a bit too simple. Lots of modern food contains so much energy that our internal alarm switches are blown off-line. Therefore, you don't feel full anymore and you keep eating. That is called Insulin resistance (see https://en.wikipedia.org/wiki/... ) It is hard to overeat on apples. It is easy to overeat on sweets.
Off course, the food industry just loves to create food that makes you keep eating, because that will also make you buy more of it. That is why even organic meat contains sugar and all kinds of syrup nowadays. The first step to a healthy life is to eat real food.