changes of overweight and obesity prevalence among school children in north west of iran after 3 years follow-up (2009–2011): a longitudinal study

background: obesity and overweight among children is a major public health problem in developed and developing countries and has important health and economic implications. this longitudinal study aimed to assessing the prevalence trend of overweight and obesity in west azerbaijan in north west of iran. methods: this study was a longitudinal follow-up study and was conducted in school children at 2009–2011 year. the subjects were all school children (12 years of age) that were recruited from rural and urban schools in west azerbaijan. overall, 22,820 girls and 28,763 boys were enrolled in 2009 and were followed for 3 years. a body mass index (bmi) 85th–95th percentile was classified as overweight and a bmi >95th percentile was classified as obese. all statistical analyses were performed using the excel software. descriptive statistics were used to characterize the sample in different time periods. the prevalence was calculated as the ratio of number of present cases to a given population number in a given subgroup at a given time. results: in urban schools, the prevalence of overweight among girls and boys was 118.26 and 103.9 per 1000 persons in 2009 year, respectively, and this trend was increased in both girls (152.90 per 1000 persons) and boys (125.72 per 1000 persons) in 2011. the obesity trend was increased among both girls and boys (22.26 and 26.52 among girls and boys in 2009 to 24.66 and 28.65 per 1000 persons in 2011), respectively. in rural schools, the prevalence of overweight among girls was increased from 84.5 in 2009 to 108.89 per 1000 persons in 2011, but this trend was decreased among boys (from 95.49 in 2009 to 43.9 per 1000 persons in 2011), and the prevalence of obesity among boys was increased at the end of follow-up, but this trend was decreased among girls. conclusions: overweight and obesity in children has increased. further studies are necessary to evaluate the relationship between obesity and overweight and risk factors such as dietary pattern and physical inactivity.