Role of Sedentary Behaviour and Moderate-to-Vigorous Physical Activity on Fatness Phenotypes in Children

Sedentary behaviour (SB), which is characterized by the absence or low physical movement (e.g. sitting or watching TV) and by low energy expenditure (≤1.5 METs), has been associated with detrimental health effects, such as body fatness.

Purpose To examine the bi-directional associations between objective measures of SB and moderate-to-vigorous physical activity (MVPA) with total body fat (TBF) and abdominal body fat (ABF) in 10 to 11 year-old children.

Methods TBF and ABF were assessed by dual energy x-ray absorptiometry (DXA) in 168 boys (age: 9.9±0.36 years) and 170 girls (age: 9.8±0.42 years) with ABF evaluated between L2-L4. MVPA and SB were objectively assessed with accelerometers (Actigraph, model GT1M). Multiple regressions were used for data analysis with both SB and DXA adiposity data converted into standardized z-scores.

Results SB revealed to be independently associated with TBF (β=0.161, p=0.004) and ABF (β=0.151, p=0.007), after adjustment for age, gender, and register time of the accelerometer. However, after including MVPA in the model, the associations between SB and TBF (β=0.082, p=0.266) and ABF (β=0.056, p=0.449) were no longer significant. The only variable that remained statistically significant in the model was MVPA, but only in the ABF analysis (β=-0.007, p=0.046). Considering the opposite analysis of associations, the results remained similar with TBF (β=0.153, p=0.004) and ABF (β=0.144, p=0.007) being independently associated with SB. Nevertheless, after introducing MVPA into the model, the associations between these variables were once again non-significant (β=0.046, p=0.266 and β=0.031, p=0.449 for TBF and ABF, respectively).

Conclusions Associations of SB and phenotypes of fatness such as TBF and ABF were bi-directional. Regardless of the direction of these relationships, the results highlight the importance of decreasing SB, and increasing MVPA especially in order to improve the ABF phenotype in boys and girls 10 to 11 year-old.