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Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9 to 10 year old Portuguese children

¹Faculty of Human Movement, Technical University of Lisbon, Portugal
²Sports Medicine, Norwegian School of Sports Sciences, Oslo, Norway
³University of Madeira, Portugal
⁴Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
⁵Sport and Exercise Science, Bath University, Bath, UK
⁶Medical Research Council Epidemiology Unit, Cambridge, UK
⁷School of Health and Medical Sciences, Örebro University, Örebro, SWEDEN

Ulf.Ekelund{at}mrc-epid.cam.ac.uk

ABSTRACT

Objective: We examined the independent relationships between objectively measured physical activity and insulin resistance in Portuguese children.

Research Design and Methods: School-based, cross-sectional study in 147 randomly selected girls (9.8 ± 0.3 years; 27.8 ± 9.3 % body fat) and 161 boys (9.8 ± 0.3 years; 22.0 ± 9.2 % body fat). Physical activity was assessed by the Actigraph accelerometer for 4 days and summarised as time spent sedentary (accelerometer counts < 500/min), in light intensity (accelerometer counts 500–2000/min) and moderate and vigorous intensity activity (accelerometer counts >2001/min). We measured total and central fat mass by dual X-ray absorptiometry. Insulin resistance was expressed as the Homeostasis Model Assessment score.

Results: Time (min/d) spent sedentary was significantly and positively associated with insulin resistance (B–coefficient=0.001, 95% CI; 0.0002; 0.002, p=0.013). Time spent in MVPA (B–coefficient=–0.002, 95% CI;–0.003;–0.001, p=0.0009) and overall physical activity (B–coefficient=–0.001, 95% CI;–0.008; 0.003; p<0.0001) were significantly and inversely associated with insulin resistance. All associations remained statistically significant, although were attenuated after further adjustments for gender, birth weight, sexual maturity and total or central fat mass (p<0.03).

Conclusions: Physical activity is associated with insulin resistance independent of total and central fat mass in children. Our results emphasise the importance of decreasing sedentary behaviour and increasing time spent in moderate and vigorous intensity activity in children, which may have beneficial effects on metabolic risk factors regardless of the degree of adiposity.

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