Purpose: This study aimed to verify the agreement between body mass index (BMI) and body fat in adolescents with different physical activity (PA) levels. Method: This cross-sectional study collected body fat data in 118 adolescents (aged 10 to 14 years) estimated using air-displacement plethysmography (ADP). Body mass 10 and height were used to calculate BMI. Physical activity levels were measured objectively by accelerometers. Results: For boys with low PA, BMI overestimated body fat values measured by ADP (mean error = -0.42; p = .018) which also occurred in group high PA (mean error = -0.76; p = .001). For girls, BMI underestimated body fat values measured by ADP values in group high PA (mean error = 0.43; p = .001) and low PA (mean error = 0.72; p < .001). Conclusion: It is recommended that researchers and practitioners 15 cautiously interpret BMI results, especially considering that most adolescents do not practice enough PA.
Keywords: Accelerometry; adolescents; anthropometry; body composition.