Populations undergoing extensive and rapid socio-economic transitions including historically disadvantaged communities face an increased risk of type-2 diabetes (T2D). In recent years, sedentary behavior and physical inactivity have been considered modifiable determinants when developing primary prevention programs to reduce T2D incidence. Reunion Island is a French overseas department with an increasing T2D population and a high level of socio-economic inequality. The objectives of our study were to identify the individual, social, and environmental factors associated with sedentary behavior and physical inactivity among the Reunion Island adult population, and to highlight these findings in order to propose T2D primary prevention strategies aiming at alleviating local social inequalities in health (SIH). In 2021, we conducted a population-based cross-sectional telephone survey using random sampling. Participants included adults over 15 years old living in ordinary accommodation on Reunion Island (n = 2,010). Using a sequential approach, multinomial logistic regression model (explaining 3 profiles of interest: sedentary/inactive, sedentary/active, non-sedentary/inactive), and sampling-design weighted estimates, we found that 53.9% [95% confidence interval: 51.1 to 56.7%] of participants had sedentary behavior and 20.1% [95% CI: 17.8 to 22.5%] were inactive. Abandoning physical activity due to the COVID-19 pandemic (p<0.001), final secondary school diploma or above (p = 0.005), student as professional status (p≤0.005) and living in fewer poor neighborhoods located far from city centers (p = 0.030) were four conditions independently associated with sedentary/inactive and/or sedentary/active profiles. Based on these findings, to help reduce SIH, we used a typology of actions based on the underlying theoretical interventions including four main action categories: strengthening individuals (using person-based strategies), strengthening communities, improving living and working conditions, and promoting health-based macro-policies. Our findings suggest several directions for reducing lifestyle risk factors and enhancing T2D primary prevention programs targeting psychosocial, behavioral, and structural exposures.