Physical activity, BMI and body weight perception among 15-year-old boys and girls in Poland in the light of international comparisons.

Background: The wrong subjective assessment of body mass may have consequences for the health, quality of life and proper functioning of adolescents in society.

Aim: The purpose of the study is to provide a detailed analysis of the discrepancies between the objective and subjective assessment of body mass by 15-year-old boys and girls in Poland against the background of international statistics and to assess the effect of physical activity on the level and directions of these discrepancies.

Material And Methods: The data concerned 72037 schoolchildren from 42 countries, including 1484 in Poland. The measure of objective body mass was the BMI categorized according to Cole's criteria. Research focused on the relation between the mean BMI and the subjective perception of their body mass by adolescents and the discrepancy in this assessment. In addition, the level of physical activity (MVPA) was taken into account.

Results: In Poland the percentage of adolescents with overweight was lower than the international average and amounted to 12.3% vs. 15.2%. The percentage of 15-year-old boys with overweight in Poland is nearly three times higher than girls of the same age (18.7% vs. 6.5%) and is at the mean level for Health Behaviour in School-aged Children (HBSC) countries. According to international statistics, the percentage of adolescents who consider themselves overweight is 32.7%, which is two times higher than the percentage of actual excess body weight. Polish girls are systematically first in the ranking of those who consider themselves too fat. It was demonstrated that Polish girls with a normal BMI for their age who consider themselves too fat are on average slimmer than their peers in other countries. There is a correlation between Moderate-to-Vigorous Physical Activity (MVPA) and the accuracy of self-assessment of body mass and the type of mistakes made in that assessment, which is more clearly marked among boys.

Conclusion: There are clear geographical and cultural differences in the level of discrepancies between the objective and subjective assessment of body mass among teenagers. Physical activity modifies these discrepancies.