Tehran University of Medical Sciences Journal of Nutritional Sciences and Dietetics 5 1-2 2019 01 01 32 39 Zahra Abdollahi Department of Nutrition, Mofid Children’s Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran Ali-Akbar Sayyari Pediatric Gastroenterology, Hepatology and Nutrition Research Center, Research Institute for Children Health, Mofid Children’s Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Beheshteh Olang Department of Nutrition, Mofid Children’s Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. & Pediatric Gastroenterology, Hepatology and Nutrition Research Center, Research Institute for Children Health, Mofid Children’s Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Hassan Ziaodini Department of Health Psychology, Research Center for Education Studies, Ministry of Education, Tehran, Iran. Hossein Fallah Department of Nutrition, Mofid Children’s Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran Zahra Abasalti Department of Nutrition, Provincial Health Center, Mashad University of Medical Sciences, Mashad, Iran. Fereshteh Fozouni Department of Nutrition, Provincial Health Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Sakineh Jafari Department of Nutrition, Provincial Health Center, Isfahan University of Medical Sciences, Isfahan, Iran. Farhad Lashkarlouki Department of Nutrition, Provincial Health Center, Golestan University of Medical Sciences, Gorgan, Iran. Mahnoush Sahebdel Department of Nutrition, Provincial Health Center, Ahvaz Jondishapur University of Medical Sciences, Ahvaz, Iran. Arash Siadati Department of Nutrition, Provincial Health Center, Ardabil University of Medical Sciences, Ardabil, Iran. Hamideh Aslani Department of Health Psychology, Research Center for Education Studies, Ministry of Education, Tehran, Iran. Roya Riahi Department of Pediatrics, Child Growth and Development Research Center, Research Institute for Primordial Prevention of Noncommunicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran. Motahar Heidari-Beni Department of Pediatrics, Child Growth and Development Research Center, Research Institute for Primordial Prevention of Noncommunicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran. Roya Kelishadi Department of Pediatrics, Child Growth and Development Research Center, Research Institute for Primordial Prevention of Noncommunicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran. 2019 09 02 2019 12 27 Background: This study aimed at examining the effect of an educational program on children’s and adolescents’ knowledge of, attitude toward, and practice of healthy lifestyle habits. Methods: This was a quasi-experimental nationwide intervention carried out as part of the Iran-Ending Childhood Obesity (IRAN-ECHO) program. Participants were selected from six cities of Iran. The sample size was calculated to be 1264 for each city. Knowledge of, attitude toward, and practice of healthy nutritional habits were measured at baseline and following the intervention. A physician and a dietitian provided recommendations on healthy diet, screen time, physical activity, and sleep time. Behavioral therapy was given when necessary. Results: The prevalence of overweight or obesity was 7.6%. The frequency of students with desirable knowledge was significantly greater after the intervention compared with baseline (32.5% vs 24.8%, p = 0.02). The mean score for attitude toward obesity complications significantly increased from 73.09 to 74.78 (p = 0.03). There was also a significant increase in the mean score for the practice of low consumption of unhealthy snacks after the intervention (difference = 1.63, p = 0.03). The mean score for participation in mild physical activity increased from 50.67 to 65 after the intervention (p < 0.001). However, there were no significant changes in the number of students with desirable attitude and practice following the intervention (p> 0.05). Conclusion: The study shows that an educational intervention based on WHO-ECHO recommendations can be useful for improving the knowledge of a healthy lifestyle in children and adolescents. Over time, it might lead to a positive attitude and behavior toward a healthier lifestyle. Continued professional education and implementation of guidelines for the prevention and management of early childhood overweight and obesity are suggested. https://jnsd.tums.ac.ir/index.php/jnsd/article/view/284