Reference data for body composition parameters in normal weight Polish adolescents: results from the population- based ADOPOLNOR study

The purpose of this study was twofold: (i) to develop age- and sex-specific reference data on body composition parameters, including fat-free mass (FFM), body cell mass (BCM), total body water (TBW), muscle mass (MM) and fat mass (FM), and indices of FFM, BCM and FM, and (ii) to assess potential differences in these parameters between male and female adolescents aged 10-18 years. Data used in this analysis were obtained from the ADOPOLNOR study, a population-based transdisciplinary cross-sectional survey focussing on the health and quality of life of adolescents, conducted in the western part of Poland. A homogeneous subsample of 4,037 participants of participants of normal weight from all types of schools and socioeconomic backgrounds, including 2,005 male and 2,032 female adolescents, was selected on the basis of BMI for the analyses. Bioelectrical impedance analysis (BIA) was used to assess various components of the body. The RefCurv software package, version 0.4.2, was used to calculate age- and sex-specific centile values and to plot smoothed centile curves. Despite the observation that body composition parameters generally increased with age during adolescence, with the exception of FM%, which decreased in boys, there was a clear sexual dimorphism. Boys had consistently higher values for FFM, BCM, TBW,, and MM compared to girls, with statistical significance (p<0.01) noted from the age of 13 (FFM) or 14 (BCM, BCMI, MM) years or throughout adolescence for parameters such as TBW and FFMI. On the contrary, boys consistently had significantly lower values for FM, FMI and FM%, indicating a lower proportion of body fat compared to girls. Centile values and curves were obtained separately for boys and girls and for each chronological age category and compared with other European samples of adolescents. Conclusion: The development of reference data for body composition in Central European adolescents is of paramount importance. These local reference data provide a contextualised framework that takes into account the unique physiological and environmental factors within the region. They can serve as an invaluable tool for research, screening and clinical assessment of nutritional status in adolescents.