Adherence to the EAT–Lancet planetary health diet and its associations with obesity and health-related quality of life in Iranian adolescents: a cross-sectional study

BACKGROUND: Adolescent obesity and diminished health-related quality of life (HRQoL) remain critical global issues and are further complicated by the urgent need for sustainable diets amid climate change. The Planetary Health Diet Index (PHDI), which is based on EAT-Lancet recommendations, connects human nutrition with environmental sustainability. METHODS: This cross-sectional study of 1,038 students (mean age, 15.13 ± 1.53 years) from the 2024-2025 academic year assessed dietary intake via a validated 147-item food frequency questionnaire. Anthropometrics followed standard protocols, and HRQoL was evaluated with the Pediatric Quality of Life Inventory™ Version 4.0 Generic Core Scales (PedsQL). Adjusted binary logistic regression models, controlling for age, sex, ethnicity, socioeconomic status, sleep duration, screen time, and energy intake, were used to analyze associations (SPSS version 28). RESULTS: The mean PHDI score was 50.79 (95% CI, 50.13-51.45; range, 19.66-94.46). According to the adjusted analyses, the highest quartile was associated with lower odds of general obesity (OR, 0.44; 95% CI, 0.24-0.81), abdominal obesity (OR, 0.56; 95% CI, 0.36-0.89), and impaired HRQoL (OR, 0.41; 95% CI, 0.24-0.70; all P < 0.05). CONCLUSION: Greater PHDI adherence is associated with improved anthropometric status and HRQoL in adolescents, underscoring the potential of sustainable diets for holistic health promotion. Longitudinal studies are needed to establish causality and generalizability.