It's not ALL in our heads....

Although we do experience head hunger, there is also a physiological reason why we crave crap food if we eat crap food.....

http://health.yahoo.net/articles/nutrition/photos/10-most-addictive-foods#0

 

There are many great books written on this topic and many food scientists whose only job is to manipulate the ingredients in the processed foods in ways that will increase our use of them.  There is an army of people from food scientists to marketers and placement consultants in supermarkets who make a living from getting to eat processed foods.  The truth is that it is very hard to resist it because it is engineered, purposefully to make it hard for you to resist it in the first place and to make sure that once you start eating it, you don't stop.  The only real solution is to give it up.  The other issue is that carbs simple make you want to eat more and to eat more carbs.  It takes between four days and a full week to detox from this effect but once you do, eating protein and veggies becomes rather easy and you even find that you are less hungry and need less food to stay full.  You are right, it is not all in you head!

I second Elina's comments. I once heard a lecture by a man (who is now one of the foremost experts on eating whole/unprocessed foods) and he explained his many years working for Kraft. His job was to addict you to horrible foods. Scary.