The increasing prevalence of child obesity in many developed countries emphasises the need to promote healthy eating and active lifestyles to children. Previous research indicates that a peer-modelling and rewards intervention produces substantial increases in children's fruit and vegetable consumption. The aim of the current thesis was to develop an intervention based on the same behavioural principles to increase children's physical activity. In the first instance, it was important to identify a valid, objective measure of children's physical activity. In Study 1, the electronic pedometer distinguished between children's play activities that ranged from sedentary to very vigorous, and showed good correspondence with heart rate and self-report measures of effort. In Study 2, children's habitual physical activity was measured over the entire day using pedometers and accelerometers. High-active children were more active than low-active children during both school-time and leisure-time, suggesting that an intervention targeting total physical activity throughout the day is most appropriate.
SUMMARY The increasing prevalence of child obesity in many developed countries emphasises the need to promote healthy eating and active lifestyles to children. Previous research indicates that a peer-modelling and rewards intervention produces substantial increases in children's fruit and vegetable consumption. The aim of the current thesis was to develop an intervention based on the same behavioural principles to increase children's physical activity. In the first instance, it was important to identify a valid, objective measure of children's physical activity. In Study 1, the electronic pedometer distinguished between children's play activities that ranged from sedentary to very vigorous, and showed good correspondence with heart rate and self-report measures of effort. In Study 2, children's habitual physical activity was measured over the entire day using pedometers and accelerometers. High-active children were more active than low-active children during both school-time and leisure-time, suggesting that an intervention targeting total physical activity throughout the day is most appropriate. In Study 3, an intervention incorporating peer-modelling (i. e., the Fit n' Fun Dudes), contingent rewards, and pedometer feedback was implemented in a school- setting with 9- to I I-year-old boys and girls as participants. The intervention produced substantial increases in the physical activity of both boys and girls, which were well maintained at 12-week follow-up, particularly among the least active girls in the sample. In Study 4, the intervention was implemented by parents in the home context and 9- to I I-year-old girls took part. They showed substantial increases in physical activity during the intervention and remained more active at follow-up relative to baseline. The physical activity of parents also increased following the introduction of pedometer self-monitoring procedures. There is great potential for future research to combine the healthy eating and physical activity interventions to provide a two-pronged approach to preventing child obesity.