Role of cardiorespiratory fitness on the association between physical activity and abdominal fat content in adolescents: the HELENA study.

We examined the role of cardiorespiratory fitness (CRF) on the association between physical activity (PA) and abdominal fat content in adolescents. Abdominal fat content was measured by waist circumference, waist-to-height ratio and dual energy X-ray absorptiometry (DXA) at 3 regions (R1, R2, and R3). PA and CRF were assessed by accelerometry and the 20 m-shuttle run test, respectively. Vigorous PA was inversely associated with waist circumference and waist-to-height ratio (β from -0.149 to -0.197; p<0.05). In both CRF groups (i. e., low and high), vigorous and moderate-to-vigorous PA (also average PA in the low CRF group) were inversely associated with abdominal fat (i. e., R1, R2 and R3; β from -0.146 to -0.244; p<0.05). This association did not differ according to CRF group (P for interaction >0.05), yet the percentage of variance in abdominal fat content, when assessed by DXA, explained by PA was slightly higher in adolescents with low CRF (3-8%) compared to those with high CRF (2-4%). The findings indicate that there is not a clear interaction effect of CRF in the association between PA and abdominal fat in adolescents, yet slightly stronger association was observed in the low fit group.