Relationships of physical activity with metabolic syndrome features and low-grade inflammation in adolescents

Aims/hypothesis: Physical activity has beneficial effects on symptoms of the metabolic syndrome and low-grade inflammation in adults. These associations have rarely been studied in adolescents. Moreover, it has not been established whether they depend on adiposity, fat localisation and adipokines. Subjects, materials and methods: We used cross-sectional data of 640 12-year-old adolescents participating in the Intervention Centred on Adolescents' Physical Activity and Sedentary Behaviour Study (ICAPS). Weight, height, body fat mass and WHR were measured. Metabolic syndrome components, two inflammatory markers (IL-6 and C-reactive protein), plasma leptin, adiponectin and soluble TNF-α receptor 1 (sTNF-α R1) were determined. Insulin resistance was estimated by homeostasis model assessment (HOMA) and energy expenditure due to organised leisure-time physical activity (PAE) assessed by questionnaire. Results: The metabolic syndrome was present in 5.8% of the adolescents. After adjustment for sex, sexual maturity and socio-economic status, a beneficial relationship between PAE and all metabolic syndrome features was found, but only the associations with HOMA and IL-6 were independent of body fat mass and WHR. Adjusted means from the lowest to the highest tertile of PAE were 1.99, 1.80 and 1.78 for HOMA (p=0.04), and 0.88, 0.69 and 0.70 pg/ml for IL-6 (p=0.02). PAE was inversely associated with leptin, independently of body fat mass and WHR (p<10^-2), but not with adiponectin or sTNF-α R1. Further adjustment for adipokines did not change the relationships of PAE with HOMA and IL-6. Conclusions/interpretation: In adolescents, physical activity is inversely related to HOMA and IL-6, independently of adiposity and fat localisation. These relationships are not accounted for by adipokines.