Introduction: It is well known that adequate nutritional intake and proper diet are important for optimum athletic performance. F-MARC Nutrition for Football: a practical guide to eating and drinking for health and performance was published in Sept. 2005 and targeted to football players. However, effective instructional methods to achieve these goals have not been reported. Therefore, it is essential to determine the factors that regulate dietary behavior. The aim of this study was to elucidate the relationship between stage of change related to proper diet implementation, dietary nutritional status, and psychological factors in football players. Methods: This cross-sectional study used a questionnaire covering stage of change, decisional balance, self-efficacy, social support, and behavioral skills associated with proper diet implementation. Ten hundred and ninety-five U-15 footballers in the J. League completed the questionnaire and submitted 3-day food records. Results & Discussion: Social and psychological factors were significantly related with stage of change for proper diet implementation. Positive perceptions (pros), self-efficacy, social support, and behavioral skills were higher in later stages compared to earlier stages. Most nutrition-related intake including major nutrients, vitamins, and minerals during the later stage was also higher compared to earlier stages. The results of this study were based on a cross-sectional survey, and a longitudinal study is needed to validate the relationships between these variables. Conclusion: The social and psychological factors revealed in this study might represent predictors or facilitators of desirable eating behavior in J. League U-15 football players.
