Objective: To objectively measure habitual physical activity and sedentary behaviour in a clinical sample of obese children and to compare with age- and sex-matched non-obese controls.
Design: Pairwise comparison of obese children matched for age and gender with non-obese controls.
Subjects: A total of 116 obese children (body mass index (BMI)> or =98th centile) and 53 non-obese control children (BMI<85th centile). Controls were matched with 53 of the obese children (mean age 8.6, s.d. 2.0 years; 25 M and 28 F).
Measurement: Habitual physical activity and sedentary behaviour were measured over a 7-day period using CSA accelerometers. Total physical activity (mean accelerometry count per minute (c.p.m.)), percentage of monitored time in sedentary behaviour, light and moderate to vigorous intensity physical activity (MVPA) were compared.
Results: Obese children (n=116) spent on average 80.4% of their monitored time in sedentary behaviour and 2.5% of their monitored time in MVPA. Total activity (mean c.p.m.) was significantly higher in the non-obese group (n=53) than the obese group (n=53), 729 vs 648 c.p.m.; 95% confidence interval (CI) 7, 155. Time spent in sedentary behaviour averaged 80.9% (s.d. 6.6) in the obese group and 79.3% (s.d. 6.2) in the non-obese group, with no significant between-group difference (95% CI -3.9, 0.6). Light intensity activity was similar in the obese and non-obese groups (15.9 vs 17.3%; 95% CI -0.3, 3.0). Participation in MVPA was significantly higher in the non-obese vs obese group (3.9 vs 2.4%; 95% CI 0.6, 2.0).
Conclusion: This study supports the hypothesis that a clinical sample of obese children is less physically active than non-obese children, although the difference in total activity and MVPA between the groups was small.