Background: Black adults face significant health disparities, with sedentary behavior and physical inactivity contributing to these inequities. While social support plays a key role in increasing physical activity and reducing sedentary behavior, its specific influence on these behaviors in Black adults is not fully understood. Specifically, although social support can alleviate stress and loneliness—both of which are known to hinder physical activity (PA) and promote sedentary behavior—the ways in which stress and loneliness mediate the effects of social support on these behaviors in Black adults remain unclear. Understanding these mechanisms is crucial for developing culturally relevant interventions that empower Black adults to adopt more active lifestyles and reduce health disparities.

Objectives: This study investigated the indirect relationship between perceived social support and health behaviors (PA and sedentary behavior) mediated by stress and loneliness among Black adults.

Methods: We performed a cross-sectional analysis of Project CHURCH, a community-based participatory study by The University of Texas MD Anderson Cancer Center in partnership with Black churches in Houston, developed to engage the Black community in overcoming cancer research participation barriers. Structural equation modeling assessed direct and indirect effects of the predictor on the outcome via the mediator, adjusting for covariates in 1,827 Black adults. Bootstrapping with 2,000 iterations provided standard errors (SEs) for effect estimates. Missing data were addressed using missForest imputation.

Results: Social support had a significant indirect effect on PA (b=0.004, SE=0.002, p=0.018) and sedentary behavior (b=-0.927, SE=0.369, p=0.012) via perceived stress. Specifically, higher social support reduced stress, which was associated with more PA and fewer sedentary hours. Social support also indirectly influenced PA (ab=0.007, SE=0.003, p=0.021) and sedentary behavior (ab=-3.062, SE=0.653, p<0.001) through loneliness; social support reduced loneliness, which was associated with increased PA and fewer sedentary hours.

Conclusions: Higher levels of social support are linked to reduced physical inactivity and sedentary behaviors among Black adults, with stress and loneliness as mediators. Future research should aim to strengthen social support networks to reduce psychosocial stressors and loneliness and improve health outcomes in this underserved population.