Parent–Child Concordance in Mediterranean Diet Adherence and Fast-Food Consumption: An Exploratory Study of Portuguese Families

Background/Objectives: Parent–child dietary resemblance is well documented, but concordance in Mediterranean Diet adherence and fast-food consumption within the same family dyads remains underexplored in Portugal. This exploratory study examined parent–child associations across these complementary dietary dimensions. Methods: This cross-sectional study included 85 parent/guardian–child dyads recruited by convenience from two Portuguese basic education schools. Parents/guardians completed an online questionnaire for themselves and their child. Mediterranean Diet adherence was assessed using MEDAS and KIDMED. Associations were examined using Spearman correlations with bootstrap 95% confidence intervals, and fast-food concordance using exact agreement and weighted Cohen’s kappa. Multivariable linear and ordinal logistic regression models were also fitted. Results: Parental MEDAS was positively associated with child KIDMED (rho = 0.283, 95% CI 0.080–0.482, p = 0.009) and inversely with child fast-food consumption (rho = −0.304, 95% CI −0.491 to −0.094, p = 0.005). Parental fast-food consumption was inversely associated with child KIDMED (rho = −0.480, 95% CI −0.643 to −0.284, p < 0.001) and positively with child fast-food consumption (rho = 0.724, 95% CI 0.571–0.845, p < 0.001). Exact fast-food agreement was 76.5%, with quadratic-weighted kappa = 0.579 (95% CI 0.373–0.759). Adjusted analyses supported associations of parental MEDAS and child age with KIDMED, and parental fast-food frequency with child fast-food consumption. Conclusions: Parent–child dietary behaviours showed concordance across both dimensions, although Mediterranean Diet score concordance was modest. Larger longitudinal studies with direct assessment of both generations are needed to clarify direction and mechanisms in Portugal.