Dietary Trends and Projections Among Iranian Adults: Analysis of the Iran‐WHO STEPS Survey (2005–2021) and Modelled Estimates to 2025

INTRODUCTION: Dietary risk factors significantly contribute to the global and national burden of non-communicable diseases (NCDs). Over recent decades, Iran has experienced a nutritional transition, shifting from traditional diets to increased consumption of processed foods, salt, and sugar-sweetened beverages. While some data suggest improvements in certain dietary risk factors, overall trends remain inconsistent. With rising NCD prevalence, continuous monitoring of their determinants, particularly dietary risk factors are crucial for informing effective public health interventions. METHODS: We analysed data from eight nationally representative STEPS surveys conducted in Iran between 2005 and 2021. Using the WHO Stepwise approach to NCD surveillance, standardised, locally adapted questionnaires assessed dietary intake and sociodemographic variables among adults aged 18-65 years. Dietary risk factors included consumption of fish, fruits, vegetables, processed meats, salt, and sugar-sweetened beverages. Trends were modelled using a smoothing spline method with 1000 simulations, generating annual prevalence estimates with 95% uncertainty intervals. RESULTS: From 2005 to 2025, significant dietary changes emerged: prevalence of adequate fish consumption halved (41.6% [95% UI: 36.8-46.4] to 20.0% [12.8-27.2]), while appropriate fruit intake increased modestly (22.8% [14.9-30.7] to 28.0% [11.2-44.5]). Adequate vegetable consumption followed a bell-shaped curve, peaking at 55.5% [45.8-65.2] in 2014 before declining to 50.9% [26.7-75.1]. Appropriate processed meat consumption improved substantially (48.8% to 95.8%), as well as appropriate salt intake (29.3% to 65.0%). Appropriate Sweetened beverage consumption demonstrated a U-shaped pattern, decreasing initially before rebounding to 85.9% (85.6-85.9) by 2025. These trends remained consistent across all age strata in stratified analyses. CONCLUSION: Despite some improvements, overall adherence to dietary recommendations remains suboptimal. The reversal of early vegetable intake gains and low combined fruit and vegetable consumption highlight the urgent need for sustained, nationwide dietary interventions.