Original article
Daily physical activity related to body fat in children aged 8-11 years

Presented in part (abstract) at American Heart Associations scientific sessions Nov 13-16, 2005, Dallas, Texas.
https://doi.org/10.1016/j.jpeds.2006.02.002Get rights and content

Objective

To evaluate the association between objectively measured daily physical activity and body fat.

Study design

Cross-sectional, observational, study of 248 children aged 7.9 to 11.1 years. Abdominal fat mass and total body fat mass were measured by dual-energy X-ray absorptiometry. Daily physical activity was assessed by accelerometers for 4 days.

Results

Total body fat expressed as a percentage of body mass was inversely related to minutes of vigorous physical activity per day, for all children r = −0.38 (P < .05). Children, both boys and girls, in the highest quartile of body fat performed on average 12 minutes less vigorous activity per day compared with their counterparts in the lowest quartile. Multiple regression analysis revealed that independent factors for body fat were number of minutes of vigorous activity per day and sex.

Conclusion

Low physical activity can be a contributing factor in childhood obesity. Only longitudinal studies, however, can give more definitive information about the relation between daily physical activity and obesity.

Section snippets

Subjects

Recruitment of the study cohort has been presented previously.16 Four hundred seventy-seven children (259 boys and 218 girls) attending third or fourth grade in 4 different schools in Malmö, Sweden, received an invitation to participate in the study; 248 children (140 boys and 108 girls) aged 8 to 11 years accepted the invitation. All schools were located in middle-class residential areas. Height and body mass of all invited children were retrieved from the general health data registered by the

DXA

Whole-body composition was measured by DXA, (DPX-L version 1.3z; Lunar, Madison, Wis). Pediatric software was used for children with a weight below 30 kg. Daily calibration of the machines was executed with the Lunar phantom. One research technician performed all measurements and software analyses. Total body fat mass (TBF) and abdominal fat mass (AFM) were quantified. The automated software used to quantify AFM also included the thoracic vertebral column, which could be a potential source of

Results

Age, anthropometric, DXA, and accelerometry data are displayed in Table I. A separate analysis of anthropometric data retrieved from school records revealed no significant differences in height, body mass or BMI between children who participated in the study and those who did not. Boys who participated in the study had mean values for height, body mass, and BMI of 127.5 cm, 26.3 kg, and 16.1 kg/m2, and the corresponding values for boys who did not participate were 128.1 cm, 27.0 kg, and 16.3

Discussion

In this population of children with relatively normal body mass distribution, we found that subjects with a higher percentage body fat were significantly less active. For example, both boys and girls in the lowest quartile of BF% spent on average 12 minutes more per day performing vigorous activity, such as running, compared with their counterparts in the upper quartile of BF%. The 2 lower quartiles in activity had 3 to 4 times higher risk of being obese, but the third quartile of activity had

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    Supported by the Swedish Research Council K2004-73X-14080-04A, Centre for Athletic Research 121/04, the Malmö and Lund hospital foundations and the Region Skåne Foundations.

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