I have this theory about* low-fat diets and portion control. It goes like this: Eating food that's not dense in calories (i.e. low-fat, high-carbohydrate meals) means you need to eat a larger volume to feel full.
Proponents of low-fat diets would present this as a positive: You get to eat more for the same number of calories! The problem is that it resets your concept of what a normal portion is. Your brain is trained to think to you need more food to feel full, so when you do eat calorie-dense meals, you still want larger portions.
This would explain why the French can eat a much more calorie-dense diet than Americans and have much lower incidence of obesity and heart disease. (This is known as the French paradox, but it's only a paradox if you take for granted that fat, in particular saturated fat, is bad for you.) The portions in France are much smaller, so they eat fewer calories overall. Too, in the absence of a warped sense of portion size, more calorie-dense food is more satisfying.
Anecdotally, I think you can reset your sense of portion size by moving to a higher-fat diet (not low-carb per se, but not low-fat either).
*Yes, all my blog posts are going to start with the phrase "I have this theory about..." from now on.