There are so many factors at work, the calories in/calories out theory only holds true up to a point and even with that it's emerging to be very inexact because of what a pp also said, how our bodies deal with different types of calories is variable. Emotional eating aside, consider -
- an 8oz steak cooked rare will have less calories than same steak well done because our body has to do less work to break down the cooked steak - same as that same steak minced and cooked will have more calories than 'straight up'
Our bodies also need certain nutrients, good fat, protein, vitamins....whilst you can fill your body with hundreds or even thousands of empty calories and get enough energy to move, our body will still send hunger signals because it hasn't got the other things it needs. Appetite serves a function...
Rather than thinking purely in terms of calories think about what your body uses food for. Carbs aren't the devil but highly processed carbs main use is energy and most of us don't need so much of that. So of 500 calories of energy there may be 300 wasted and stored as fat. Of 500 calories of wholefood carbs, protein and good fat there's likely to be much less 'waste', it takes more energy to break the food down in the first place there will be fibre that passes through and helps our gut micro biome, and components are used to build and maintain muscle, to repair and regenerate cells, eyesight, brain function etc. A much bigger 'bang for your buck' calorie wise and you feel full longer as well as being healthier.
Added to which the effect sugar and highly processed food has on blood sugar/hunger signals.
Dieting and listening to a set of rules serves to disconnect us from what works for our own body and makes certain 'bad' foods seem highly desirable.
More often than not, as per certain pp's have said, people who easily maintain a healthy weight (which can also vary quite a lot from person to person and isn't necessarily what a bmi chart says), haven't dieted, they eat a high quality diet without demonising anything. They are satisfied by what they eat so in fact the crap rarely appeals and when it does that just have a little, the tendency to binge just isn't there.