Associations of Physical Activity, Vegetarian Status, and Sleep Duration with Psychological Distress in Peruvian Adults: Model-Based Indirect Associations via Dietary Self-Efficacy

Background: Psychological distress (PD) has been associated with lifestyle behaviors, including physical activity, sleep duration, and diet-related practices. Dietary self-efficacy may represent a self-regulatory correlate in these relationships; however, evidence from population studies remains limited, particularly in Peruvian adults. Objective: To examine whether dietary self-efficacy is statistically associated with the links between physical activity, sleep duration, vegetarian status, and PD in a sample of Peruvian adults. Methods: A cross-sectional study was conducted in 684 Peruvian adults. Structural equation modeling (SEM) was used to evaluate the proposed associations, adjusting for age, sex, educational level, marital status, residence, and BMI. Results: The SEM showed acceptable fit, with RMSEA and SRMR within recommended ranges and CFI/TLI slightly below 0.90 (CFI = 0.898, TLI = 0.886, RMSEA = 0.039, SRMR = 0.047). Lower dietary self-efficacy was associated with higher PD (β = 0.283, p < 0.001). Physical activity showed an indirect statistical association with lower PD via dietary self-efficacy (β = −0.043, p < 0.001) and a significant total association with PD (β = −0.085, p = 0.018). Sleep duration showed a curvilinear (U-shaped) association with PD (linear β = −0.122, p = 0.001; quadratic β = 0.124, p < 0.001), but not via dietary self-efficacy. Vegetarian status was not directly associated with PD (β = 0.002, p = 0.956), and its indirect statistical association via dietary self-efficacy did not reach conventional significance (β = 0.022, p = 0.070). The model explained 14.1% of the variance in dietary self-efficacy and 19.3% of the variance in PD. Conclusions: Lower dietary self-efficacy was associated with higher PD and captured a model-based indirect statistical association between physical activity and PD. Given the cross-sectional design, these findings should be interpreted as correlational and warrant confirmation in longitudinal or experimental studies.