Department of Endocrinology and Metabolism, Peninsula Medical School, Plymouth Campus, Plymouth, UK. brad.metcalf@phnt.swest.nhs.uk
OBJECTIVE: Recent evidence suggests that, in children, traditional markers of metabolic disturbance are related only weakly to physical activity. We therefore sought to establish the corresponding relationships with newer metabolic markers. RESEARCH DESIGN AND METHODS: This was a nonintervention longitudinal study of 213 healthy children recruited from 54 schools in Plymouth, U.K. MTI accelerometers were used to make objective 7-day recordings of physical activity at ages 5 +/- 0.3 (mean +/- SD), 6, 7, and 8 years. Overall physical activity was taken as the average of the four annual time points. The metabolic markers at 8 years were adiponectin, leptin, high-sensitivity C-reactive protein (hsCRP), and insulin resistance (homeostasis model assessment). Potential confounders included percent body fat measured by dual-energy X-ray absorptiometry and diet measured by food frequency questionnaire. RESULTS: Whereas physical activity did not correlate with insulin resistance (r = -0.01), leptin (r = +0.04), or hsCRP (r = +0.01) independently of percent body fat, it did correlate with adiponectin, but inversely (r = -0.18, P = 0.02). This unexpected inverse relationship was strongest among the less active children (physical activity < median: r = -0.30, P = 0.01) but negligible in the more active children (physical activity > median: r = +0.04, P = 0.76). Adiponectin was significantly higher (0.52 SD, P < 0.01) in the least active tertile compared with the other two tertiles. Insulin resistance, however, did not differ across the physical activity tertiles (P = 0.62). CONCLUSIONS: Adiponectin levels in children are highest among those who are least active, but their insulin resistance is no different. Adiponectin has a known insulin-sensitizing effect, and our findings are consistent with a selective effect at low levels of physical activity.