The theory of moderation is intended to be applied to healthful foods and healthful foods alone.
Moderation applied to unhealthful eating does not work in theory or in practice. All the idea of moderation does successfully is draw attention from the real issue: that there are good and bad foods, projecting the concept that all food is good food, and that we can eat whatever we want without consequence as long as it is limited.
Unfortunately this is not true. Everything that we eat has a consequence, whether positive or negative, and however potentially minute. For example, moderation would say that it is okay to eat a hamburger, as long as you trade the fries for a salad and the soda for some juice. By following this logic, all we are accomplishing is the drowning out of our unhealthful food choice with a high percentage of healthful food choices. Although partially effective, and of course better than the option which included the french fries and soda, we are ignoring the real issue. Our efforts have not changed the fact that the hamburger has a negative impact on our health. We have lessened the impact, but not changed the truth: hamburgers are bad for you.
Ignoring that the idea of moderation is inherently flawed, we can discuss the average practice of moderation. True moderation of food allows its occurrence in our diet much less often than we would like to believe. For example, moderating something like chocolate may place it in our diet once a week, or even less often. This is not how the average person approaches moderation. The average person instead uses moderation as a rationale for making constant unhealthful choices. That is, the person moderates cookies, chocolate, fast food, dairy, and etcetera. Using this “once in a while is okay” attitude leads us to constant, although perhaps different, unhealthful choices.
Moderation does not work. Some foods are bad for us and should be entirely eliminated from our diet. Some things we consider to be foods are not even really food in the first place, but sinister food-like substances and they should be avoided permanently.