The message changes belief and the rest is theory: the "1% or less" milk campaign and reasoned action.

Background: Theory-based approaches to public health interventions are useful for designing, implementing, and evaluating research. This paper describes and presents data to support the theoretical force behind the "1% or less" nutrition intervention studies.

Methods: Using the Theory of Reasoned Action (TRA), high-fat (whole and 2%) milk users were targeted. Supermarket milk sale data were collected, and randomly selected intervention and comparison community residents were surveyed via telephone to assess milk use. TRA constructs were used in the surveys that were conducted immediately before and after a 6-week mass media campaign. Campaign messages were aimed at changing behavioral rather than normative beliefs.

Results: We found significant and predicted changes in intervention participants on intention, attitude, and behavioral beliefs, but not subjective norm outcomes. A path model showed support that TRA variables mediated significant changes in self-reported milk use.

Conclusions: The analysis further validates the TRAs and supports a template using both the Principle of Compatibility and TRA to aid development and implementation of messages for effective behavior change field interventions.