Physical Activity Determinants Under the Double Burden of Malnutrition: Contrasting Pathways for Underweight and...

Chinese adolescents face a dual burden of malnutrition, yet the weight-status-specific mechanisms underlying physical activity (PA) participation remain underexplored.

We conducted a cross-sectional study among 1573 adolescents (aged 9-15 years) in Shangrao City, China. Validated scales measured social-ecological factors (family/peer support, physical environment), psychological factors (stage of change, self-efficacy, decisional balance), and PA participation. Data preprocessing utilized full information maximum likelihood to handle missing values. Confirmatory factor analysis was performed to validate the measurement model, followed by multi-group structural equation modeling to analyze pathway configurations across underweight (n = 187), normal-weight (n = 1070), and overweight/obese (n = 316) groups. Mediation effects were tested using bootstrapping with 5000 resamples.

Clear weight-specific patterns emerged. Normal-weight adolescents presented a fully functional comprehensive model where PA was predicted by the stage of change (β = 0.211, p < 0.001), friend support (β = 0.120, p < 0.001), self-efficacy (β = 0.092, p < 0.05), and perceived benefits (β = 0.095, p < 0.01). Underweight adolescents primarily relied on internal readiness driven by stage of change (β = 0.270, p < 0.001) and self-efficacy (β = 0.164, p < 0.05), with family support only indirectly influencing participation via psychological mediators. In contrast, overweight/obese adolescents showed a "socially dependent" pattern: friend support directly predicted PA levels (β = 0.136, p < 0.05), significantly enhanced self-efficacy (β = 0.370, p < 0.01), and effectively lowered perceived barriers (β = -0.165, p < 0.05). Additionally, the physical environment strongly impacted perceived benefits (β = 0.471, p < 0.01) but did not translate into action.

These findings underscore the significant differences in PA determinants across the spectrum of malnutrition, necessitating targeted public health interventions to support the Healthy China 2030 initiative.