The causal pathway effects of a physical activity intervention on adiposity in children: The KISS Study cluster randomized clinical trial

BACKGROUND Very little information on the potential mechanisms of the physical activity interventions effects on adiposity is available. We evaluated the possible mediating factors of a physical activity school-based intervention on the sum of skinfolds in children. METHODS This is a cluster randomized trial, secondary analysis of the KISS study. Children (n = 499) from the first and fifth grades were randomly assigned to intervention or control group. Adiposity was estimated by four skinfolds, aerobic fitness assessed by the shuttle run test, and insulin, triglycerides, total cholesterol, high-density lipoprotein (HDL), and glucose collected via fasting blood samples. RESULTS The intervention affected aerobic fitness (0.140 SD, 95% CI 0.011 to 0.270), triglycerides (0.217 SD, 95% CI -0.409 to -0.025), cholesterol/HDL ratio (-0.191 SD, 95% CI -0.334 to -0.047), glucose (-0.330 SD, 95% CI -0.538 to -0.121), and skinfolds (-0.122 SD, 95% CI -0.189 to -0.056). No intervention effect on insulin was found. We observed that changes in aerobic fitness impacted children's triglycerides and cholesterol/HDL ratio and consecutively the glucose levels mediating 30% of the intervention effect on skinfolds. CONCLUSIONS Our findings provided evidence of the positive metabolic distress caused by a physical activity intervention on adiposity levels in children