Inflammatory proteins during childhood and adolescence have been shown to be predictors of cardiovascular disease in adulthood⁽Reference Juonala, Viikari and Rönnemaa¹⁾. Likewise, higher levels of body fat seem to play a pro-inflammatory role in adolescents⁽Reference Wärnberg, Nova and Moreno²⁾. However, there is limited knowledge about the role of physical activity and fitness on inflammatory proteins in adolescents. Therefore, the aim of this study was to examine the relationships between self-reported physical activity (PA), fitness, body mass index (BMI), and inflammatory proteins. A sub-sample of 193 adolescents (92 girls), aged 13–17 years old and enrolled in the AFINOS study, was selected for the current study. PA was assessed by a global activity rating (compared to others of your age and sex, how much PA do you get?). Similarly, fitness was self-reported by the following question: how is your physical fitness? Both PA and fitness assessments were rated on a 5-point scale ranging from 1 (much less active/very bad) to 5 (much more active/excellent). Weight and height were also obtained by self-report and BMI was calculated (kg/m²). C-reactive protein (CRP, mg/dl), ceruloplasmin (mg/dl) and complement factors C3 and C4 (g/l) were determined, and logarithmic or square roots transformations were applied when necessary. Student's t test showed no differences between sexes regarding age and BMI. Adolescent boys were more active and fit than girls (both P=0.001). No sex differences were found for inflammatory proteins, except for ceruloplasmin, adolescent girls reaching higher levels than boys (P=0.002). PA was significantly related with fitness (r=0.546, P<0.001) but not with BMI (r=−0.132, P=0.077) after controlling for age and sex. Fitness was also related with BMI (r=−0.301, P<0.001) after controlling for age and sex.

Table 1. Partial correlations controlling for age and sex (n=193)

*P<0.05.

PA was not significantly related/associated with inflammatory proteins, but borderline significances were found with ceruloplasmin (P=0.066) and C3 (P=0.072). On the contrary, fitness and BMI were significantly related with all the inflammatory proteins tested. When BMI was included as confounder, fitness was only significantly related with celluloplasmin (r=−0.195, P=0.008) and C3 (r=−0.216, P=0.003). These results suggest that PA has a potential beneficial effect on low-grade inflammation in adolescents due to its role on fitness.