Introduction and objective:
Body height, body weight, and body mass index (BMI) are key indicators of physical development and sensitive markers of long-term environmental and socio-economic conditions. This study aimed to assess 35-year secular trends in body height, body weight, and BMI among girls living in rural areas of eastern Poland and to evaluate their public health implications in a predominantly agricultural region.

Material and methods:
The study included 11,764 girls aged 7–15 years examined in five cross-sectional surveys conducted in 1986, 1996, 2006, 2016, and 2021 in the same rural schools. Anthropometric measurements were performed in accordance with ISAK recommendations. BMI was calculated and classified using international cut-off points proposed by Cole et al. Secular trends were analyzed using one-way ANOVA with post hoc Games–Howell tests and linear regression, while BMI category distribution was assessed using the chi-square test.

Results:
A systematic increase in body height and body weight was observed across all age groups. Between 1986 and 2021, mean body height increased by 7.66 cm and mean body weight by 7.03 kg, with the greatest dynamics occurring during the peripubertal period. Mean BMI increased by 1.37 kg/m². A marked shift in BMI category distribution was observed, characterized by an increasing prevalence of overweight and obesity and a decline in the proportion of girls with normal body weight.

Conclusions:
The findings confirm persistent secular trends in somatic development among girls from rural areas of eastern Poland and indicate a growing public health challenge related to overweight and obesity, highlighting the need for targeted preventive strategies in rural populations.