Back when he was struggling to overcome bulimia, Elton John once said that he used to eat an enormous serving of curry thinking only about eating the next one. He said something to the effect that his mind was on the upcoming second serving before the first one was in the toilet. The point of what he was saying was that he wasn't even enjoying the first one, but rather focusing on getting more.
I mention this because I have also had many times where my focus was on the quantity of what I could eat, not on what I was actually eating. I could enjoy a candy bar more if I knew there was more waiting for me. The sheer notion that another round was available made eating the first one more gratifying. It's as if I couldn't enjoy anything as well or as much unless I knew there was a "buffer" zone of more on hand. Rather than deriving value from the actual sensory delight of the food I had in hand, I focused on the entire quantity.
One of my psychology professors so long ago once tried to make this point in a different way. He said that 'fat people think about food all of the time, except when it's right in front of them.' I found what he said insulting and judgmental, and I immediately rejected it as yet another thing that people without weight problems said about those with them because they didn't really understand us. The fact of the matter is, he was right, but how he said it and who it was coming from ensured that I would reject the message.
This notion of extracting pleasure only from copious amounts of food or feeling dissatisfied with a small portion is something that pervades a lot of Western cultural thinking. You often hear people complain about recommended serving sizes on food packages and say that the companies conceptualize a serving size as far too small to satisfy as a means of skewing nutritional information so that it appears more favorable. Perhaps the fault lies not with our food manufacturers, but in ourselves.
"Enough" is a highly subjective term based on body frame size, activity levels, and gender, but the truth is that most of us have formed our ideas of how much food is enough to satisfy (regardless of food type) based on cultural norms and life experience. If you are served huge portions in restaurants, you come to think of that as "enough". If your family eats heaping amounts of food, that is what you tend to think of a "enough". The bigger the cultural serving size norms are, the more people will require to satisfy their conceptualization of what portions they should eat. In many cultures, the norm for portion sizes is far smaller than that in the U.S., and that is why so many American tourists complain about them.
Of course, people like old Elton and I have disordered eating. If we are focusing on the next serving while we're supposed to be enjoying the first one, we're dealing with an issue that is beyond portions. It has to be addressed before portion control can be considered. Frankly, I've thought about this and I have not come up with a definitive explanation as to what causes this sort of thinking. Perhaps it's about growing up poor and trying to get your share. Perhaps it's about needing a feeling of being over-full or extracting gratification from the oral sensation of eating more so than the enjoyment of the food itself. Perhaps I starved to death in a past life and that part of my soul won't be gratified until it has eaten enough for both lives.*
I don't know what caused this tendency to attend to the food I don't have rather than what I do have. However, for me, the cure was mindful eating and a fair amount of self-induced therapy where I kept telling myself that "more is not going to be better." And the truth is that more really isn't better. Paying attention to the food is better. I'm doing this more and more with every bit of food I eat and it really does help. I don't know if the root cause may yet come back to bite me in the ass and I may find my ability to focus on what I am currently eating unraveling. For now, I just want to be aware that it was once the case, and could be again unless I continue to cultivate a different perspective every time I approach food.
*For the humor impaired, that is a joke.