Re: your theory... I personally question the whole concept of addiction, whether to food or alcohol or cigarettes or whatever. I believe there are various degrees of attraction toward a substance. If you happen to be highly attracted to alcohol, you'll have trouble moderating your intake. Same goes for food. I think some of us just like food more than others, just as some people like booze or sex more than others. Who knows why?
We all INTERPRET stimuli differently. For example, I enjoy the feeling of being really full. Someone else may dislike that very same feeling. I think the difference lies more in our neurology (the way we interpret the feeling) than in the elasticity of our stomach muscles or even our leptin levels. Just as one person may love the colour purple and another hate it. Same wavelength, same stimulus to the eyes and brain, different interpretation.