Nutrition Label Utilization, Dietary Self-Management, and Health-Related Quality of Life Among Korean Adults: A Two-Part Model Analysis of Nationally Representative Survey Data

Background: Health-related quality of life (HRQoL) is a central outcome measure in population health research, yet empirical investigations directly linking nutrition label utilization to HRQoL remain limited, particularly in East Asian contexts. This study examines the associations between nutrition label use, dietary control, and HRQoL among Korean adults while accounting for the pronounced ceiling effect inherent in EQ-5D utility scores. Methods: Data were drawn from the Korea National Health and Nutrition Examination Survey (KNHANES) 2024 (N = 5215 adults aged 19–80). HRQoL was measured using the EQ-5D-3L with Korean time trade-off weights. Nutrition label use was operationalized as a composite index (0–3). Given that 48.0% of the weighted sample reported perfect health, a two-part model was employed: Part 1 applied survey-weighted logistic regression predicting perfect health, while Part 2 applied survey-weighted OLS regression restricted to those with imperfect health (n = 2713). Results: In Part 1, nutrition label use was not significantly associated with perfect health (OR = 1.057, p = 0.124), whereas dietary control was negatively associated (OR = 0.819, p = 0.009), suggesting reverse causality. In Part 2, nutrition label use was positively associated with EQ-5D scores (β = 0.0047, p = 0.006). Education, income, and unmet medical need were dominant predictors. Results were robust to an alternative full-sample OLS specification. Conclusions: Nutrition label utilization was modestly and positively associated with HRQoL among Korean adults with imperfect health. Given the cross-sectional design, this association should be interpreted as exploratory and may reflect broader health-oriented characteristics, including health consciousness, self-regulatory behaviors, and health literacy, rather than the independent effect of nutrition label use alone. The findings also underscore the methodological importance of addressing ceiling effects in EQ-5D analyses.