Association of the planetary health diet index with overweight and obesity among patients with diabetes mellitus in a cross sectional study

The Eat-Lancet diet, which encourages a shift towards plant-based foods and reduced intake of animal products, has been proposed as a solution to improve both human health and environmental sustainability. This study explores the association between Planetary Health Diet Index (PHDI) adherence and the risk of overweight or obesity in type 2 diabetes (T2D) residing in Tehran, aiming to determine whether this diet can serve as a dual-purpose strategy for managing weight and promoting planetary health. A total of 210 participants were recruited in this cross-sectional study. Dietary information was gathered via a validated 168-item food frequency questionnaire, and PHDI score was derived from 16 food groups. Anthropometric assessments were performed following standard procedures to identify overweight or obesity. Associations between PHDI and outcomes were examined using logistic regression and restricted cubic spline models. Study participants had a mean age of 62.15 ± 8.60 years, and 70% were female. PHDI was categorized into tertiles, with 33.3% of individuals in the highest tertile. In fully adjusted logistic models, high PHDI adherence was associated—though not significantly—with lower odds of overweight/obesity (OR: 0.90; 95% CI: 0.42, 1.95) and obesity (OR: 0.90; 95% CI: 0.37, 2.20) compared to low adherence. Additionally, we did not observe any non-linear association between PHDI and odds of overweight/obesity in T2D patients, after adjustments for potential confounders. Given the absence of a statistically significant link between PHDI and the likelihood of overweight or obesity, which may reflect insufficient statistical power, future studies incorporating larger cohorts and diverse populations are needed to assess the generalizability of these findings.