Interleukin-6 secretion and fat oxidation rates in children with simple obesity and different levels of physical activity

Physical inactivity is accompanied by a decrease of skeletal muscle mass and is one of the main reasons for obesity. Interleukin-6 (IL-6) acts as a paracrine and endocrine regulator of the intensity of carbohydrate and fat metabolism during exercises. The purpose of this research was to evaluate the fat oxidation rate and serum IL-6 in children with simple obesity depending on the level of daily physical activity (PA). Methods used: a cross-sectional, single-center sampling study that included 53 children aged 12 to 18 y/o (27 boys/26 girls) with obesity (SDS BMI 3.0 [2.6;3.3]) divided into two groups depending on the level of daily PA was conducted. The maximal fat oxidation (MFO) was assessed during ergometric stress testing with gas analysis. The IL-6 was assessed by ELISA at baseline and after a single physical activity. The level of daily PA was determined using the IPAQ international questionnaire Results: basal IL-6 level in children with obesity and low PA was 1.18 [0.42;1.55] pg/ml and was statistically significantly increased compared to the group of children without physical inactivity, 0.57 [0.22;0.8] pg/ml (p=0.029). The values of IL-6 after physical activity in both boys and girls with obesity and physical inactivity were statistically significantly increased compared with the group of children with obesity and moderate/high PA (p=0.032 and p=0.012 for boys and girls, respectively). The MFO in children with a low level of PA was 0.33 [0.22;0.41] g/min and did not significantly differ statistically from the group of peers with moderate or high PA (0.31 [0.25;0.36] g/min; p=0.431). Conclusion: a sedentary lifestyle in obese children leads to an increase in both basal and stimulated IL-6 secretion and is not accompanied by a decrease in maximal fat oxidation.