Dissertation title: Reinforcing fear appeals in social marketing using systematic interaction and social norms to induce physical activity. Purpose: The study aims to empirically verify the conceptual advancement of social marketing using group centered approaches to counter poor social habits that could hardly be addressed through conventional promotional techniques, persuasion and one way communication specially targeting individual behavior change. This study examines the relationship among five variables i.e. systematic interaction, social norms, fear appeals, exercise intention and physical activity behaviour. The mediating role of fear appeals and exercise intention between systematic interaction, social norms and physical activity behaviour was examined; and, also examined the long-term impact of systematic interaction on behaviour. Methodology: Integrated paradigm has been used as an effective process to better understand the phenomenon of social marketing and its empirical verification that broadens the perspective of social marketing. This longitudinal experimental study used mixed method design to examine the efficacy of interactive paradigm in social marketing. For this purpose, Activity theory (an outshoot of group dynamics) was used as a strategic tool to manage group interaction and discussion among study participants. Eligible sample was randomly assigned to treatment group and control group. The data analysis was performed using SPSS. The qualitative data was analyzed using QSR NVIVO. Findings: The results significantly revealed that the systematic interaction had a positive effect on fear appeals, physical activity, exercise intention and behavior. Fear appeals have positive and significant effect on exercise intention. Physical activity is positively related to social norms. Systematic interaction is positively related to social norms. Social norm is positively related to fear appeals. Results also showed that exercise intention mediates the relationship between fear appeals and physical activity. Findings explain new understanding and insights that strengthen the objective of using systematic interaction in social marketing as well as theoretical and practical 9 applications of the theories used as a progeny of group dynamics and substantiate the spectrum of outcome and consequential benefits that bring about efficacy of the concept of social marketing and broaden the scope in development programs. The qualitative outcomes assessment of this study depicts the linkages of the talk pattern with central word physical activity. Using activity theory results from qualitative study are grouped into four categories; artifacts producing activities, subject producing activities, rule producing activities and activities related to community transformation. Originality/Value: This is an original study using activity theory, a progeny of group dynamics employing a longitudinal mixed method research design. The participatory paradigm using systematic interaction is a key factor that enhances the value for social marketing programs to achieve desired behaviour change.