Nutrition label literacy and adolescent mental well-being: a three-wave longitudinal study of healthy eating self-efficacy and physical activity as a moderator

BackgroundNutrition label literacy may help adolescents interpret packaged-food information and develop confidence in healthier food choices, but its longitudinal association with positive mental well-being remains insufficiently understood. This study examined whether healthy eating self-efficacy statistically mediated the prospective association between nutrition label literacy and mental well-being among Chinese adolescents and whether physical activity moderated the second stage of this pathway.MethodsA three-wave longitudinal survey was conducted among Chinese adolescents aged 12–18 years. Data were collected at T1 in November 2025, T2 in January 2026, and T3 in March 2026. The final matched sample included 2,412 adolescents. Nutrition label literacy was assessed at T1, healthy eating self-efficacy at T1 and T2, mental well-being at T1 and T3, and physical activity at T2. Longitudinal mediation and moderated mediation were examined using PROCESS Model 14 logic with 5,000 bootstrap resamples, adjusting for age, gender, only-child status, residence, T1 healthy eating self-efficacy, and T1 mental well-being.ResultsT1 nutrition label literacy was positively associated with T2 healthy eating self-efficacy (β = 0.231, p < 0.001). T2 healthy eating self-efficacy was positively associated with T3 mental well-being (β = 0.201, p < 0.001) in the longitudinal mediation model. The indirect association from T1 nutrition label literacy to T3 mental well-being through T2 healthy eating self-efficacy was significant (β = 0.046, 95% CI [0.036, 0.058]). In the moderated mediation model, the T2 healthy eating self-efficacy × T2 physical activity interaction was significant (β = 0.122, p < 0.001), and the index of moderated mediation was significant (index = 0.028, 95% CI [0.020, 0.037]). Conditional indirect effects were stronger at higher levels of physical activity.ConclusionNutrition label literacy may be prospectively associated with adolescent mental well-being partly through healthy eating self-efficacy, and higher physical activity was associated with a stronger indirect pathway. Because the study was observational, these findings represent longitudinal associations rather than causal effects. These findings suggest that integrated school-based strategies combining nutrition label education, healthy eating self-efficacy enhancement, and physical activity promotion are promising, but their effectiveness should be evaluated in future intervention studies.