UNHEALTHY BODY WEIGHT IN ADOLESCENTS ESTIMATED BY APPLYING THE ANTHROPOMETRIC INDICES BMI, BMI Z-SCORE AND TMI
Keywords:
unhealthy body weight, adolescents, BMI, TMIAbstract
Background: While body mass index (BMI) remains a convenient instrument for large-scale screening of unhealthy body weight, it has significant disadvantages related to its mathematical inaccuracy and inability to distinguish fat mass from muscle mass, which is particularly problematic when interpreting results in adolescents. Some recent scientific studies proclaim other, alternative, easily applicable and with better predictive power, anthropometric indices such as tri-ponderal mass index (TMI). The aim of the study was to determine the prevalence of unhealthy body weight among teenagers aged 13-18 years by applying anthropometric indices – BMI, BMI Z-score, TMI, as well as to determine the predictive capacity of the metrics used. Materials and Methods: A cross-sectional study was conducted among 1,004 adolescents from the Stara Zagora region. The collection of demographic data and results of anthropometric measurements were carried out in the period from May 2024 to September 2025. The subsequent statistical processing was performed using the software program SPSS version 26.0 for Windows. Results: The lowest levels of underweight in the sample were reported after using the BMI Z-score (2.00%). The highest prevalence rates of underweight among teenagers (17.00%), and particularly among girls (20.71%), were measured using BMI. The lowest levels of obesity in adolescents were calculated using BMI and TMI: 3.90% and 4.50%, respectively. The highest rates of obesity among participants varying from 12.20% to 13.60% were found after applying age- and sex-specific reference values of the TMI. Conclusion: Different levels of prevalence of unhealthy body weight – underweight, overweight and obesity were reported in the sample after applying BMI, BMI Z-score, TMI, including TMI with age- and sex-specific reference values. The ROC analysis conducted in the study revealed a low discriminatory potential of both BMI and TMI, determining the propensity for inaccuracies and weak rates of reliability of anthropometric indicators when used as tools in pediatric screenings for unhealthy body weight.
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