Accelerometry-measured activity or sedentary time and overweight in rural boys and girls

The aim of this study was to examine the association between overweight and physical activity or sedentary time measured by accelerometry in rural boys and girls 7 to 19 years old.

A cross-sectional study was conducted involving 130 girls and 99 boys in elementary, middle, and high school in rural Maryland. After weight, height, and body composition were measured, children wore an Actiwatch accelerometer for 6 days. Comparisons for activity counts were made between normal and overweight or at risk for overweight (at-risk/overweight) participants (>or=85th percentile of BMI). The associations between body composition and accelerometry-defined activity levels (sedentary, light, moderate, and vigorous) were analyzed by age group for boys and girls.

Differences in total activity in counts per day or counts per minute were not observed between normal and at-risk/overweight boys or girls in all age groups. No associations between measures of body composition and time spent in an activity level were seen in boys. Fat mass and percentage fat were positively correlated to time spent in sedentary activity (range r = 0.42 to 0.54, all p < 0.01) for girls. In contrast, fat mass and percentage fat were negatively related to time spent in light activity (range, r = -0.40 to -0.51, p < 0.05) for girls.

In girls, but not boys, greater body fat is associated with greater time spent being inactive, and lower levels of body fat are associated with more time spent in light activity. Physical activity interventions targeting inactive children in rural communities are warranted.