The relative influence of sedentary behaviours versus physical activity on Body Mass Index in a sample of Australian children

Findings from studies investigating physical activity (PA) in Australian children have been mixed in terms of family-influenced motivations to exercise, as well as the subsequent influence of PA on obesity levels. Our objective was two-fold. Firstly to investigate whether a) parental modelling (children observing parents exercise and enjoyment of sport) or b) parental support (driving to sports, spectating, encouraging children to participate) had the greater influence on the child engaging in PA. Secondly to investigate the relative influence of the child’s PA and screen-time sedentary behaviours on Body Mass Index (BMI). Primary caregivers of 144 children (54% male), between the ages of 5 and 13 years, completed a retrospective seven-day questionnaire to report 1) their own physical activity levels and attitudes towards same, and 2) their child’s physical activity level, sedentary “screen-time” behaviours, and child’s BMI. Participants were primarily recruited from Sunshine Coast sporting clubs, potentially yielding a (biased) relatively active sample. Firstly, parental modelling and attitudes showed no relationship with a child’s PA levels. Measures of parental support however, combined to account for 25% of the variance in a child’s PA level. Secondly, in contrast to previous research, no significant correlation to a child’s PA levels with screen-time was shown. An independent t-test showed children in the normal BMI range (n = 86) exhibited significantly lower screen-time usage when compared with overweight children (n = 46). No significant difference in the level of PA was reported for children in both the normal and overweight BMI ranges. Parental support influenced the child’s PA level, not parental modelling. However, it was not the amount of PA that affected a child’s BMI in this sample, but rather the amount sedentary screen-time. Public health/education campaigns should focus on increasing parental awareness of idle-time on children’s weight.