Weight status of rural school youth in Poland: secular change 1986-2016.

The objective of this study was to evaluate secular changes in the Body Mass Index (BMI) and weight status of rural children and adolescents in west-central Poland across decennial surveys spanning 1986 and 2016. Participants were 8,677 boys and girls 7-15 years attending schools in 10 rural communities in 1986, 1996, 2006, and 2016. Heights and weights were measured; BMIs were calculated. Weight status was classified using International Obesity Task Force (IOTF) criteria. The sample was partitioned into three age groups (7-9, 10-12, 13-15 years) for analysis of secular change in the BMI using sex-specific analysis of covariance (ANCOVA) with age and age² as covariates, and for comparison of the prevalence of mild, moderate and severe thinness and of overweight and obesity. BMIs increased, on average, across the four surveys, but differences between adjacent surveys varied. Prevalence of severe and moderate thinness was low in both sexes, while mild thinness tended to decline over time, more so among girls. Overweight and obesity increased over time, especially in 2006 and 2016 compared to 1986 and 1996. In conclusion, secular changes in the BMI between 1986 and 2016 were significant. Age-adjusted mean BMIs suggested a gradient, 2016 > 2006 > 1996 > 1986, except in girls 13-15 years. However, changes across the decennial surveys varied. The observed changes in overweight and obesity between 1986 and 2016 were consistent with studies in Poland spanning the past two generations.