Many prevention-oriented public health policies consist of informative campaigns. These campaigns are based on the idea that information is the key to changing the practices on the part of the population thinking that, once provided with the necessary information, the subjects would change their living habits to more healthy ones. However, many studies have refuted this belief: There is a major gap between what is known about nutrition and actual everyday eating habits. An analysis is provided of this overall dynamic in the case of working-class mothers based on the results of qualitative research done in Andalusia on eating habits and discourses. Here also, we find a major gap between what is known about nutrition and actual everyday eating habits. In this article, an analysis is made of the reasons for this discrepancy as well as of the dynamics leading to continual distortions and reinterpretations of the messages given out by the health authorities. Based on these analyses, recommendations are proposed with a view to public health policy: Instead of general informative campaigns, more localized actions or actions which would have a bearing on the material living conditions would be more effective.