Over the past several decades, overweight and obesity levels have increased throughout the United States and the greatest increases among obese people occurred in persons with some college education between the ages of 18 and 29 years. This study examines the utility of theory-based messages designed to increase college students intention to eat healthy food and engage in substantive physical activity. In the present study three research objectives are presented. The first objective is to report the relative contributions of variables in an extended theory of planned behavior model (TPB, plus habit, symbolic modeling, and direct modeling) predicting behavioral intentions to eat healthy food and perform physical activity in direct or indirect ways. A second objective is to give a detailed analysis of underlying cognitive structures corresponding to specific beliefs, which discriminate most between high-intenders and lowintenders. The final objective is to report the effects of discriminated messages in changing behavioral intentions to eat a healthy diet and to perform physical activity following a classroom intervention. Overall, the current study contributes to the literature because it uses a theory-driven approach to develop discriminate messages that can be used to influence college students intentions to eat healthy food and to participate in physical activity.