Year

2008

Degree Name

Doctor of Philosophy

Department

Faculty of Education

Abstract

Childhood overweight and obesity is prevalent in both developed and developing countries world-wide, and urgent and effective response is required. To date, methodological limitations in paediatric obesity treatment trials have precluded recommendations advocating specific treatment strategies. Physical inactivity is implicated in the aetiology of obesity, however, published experimental trials evaluating interventions designed to promote physical activity in overweight and obese children have been compromised by the same methodological limitations as many paediatric obesity treatment trials. The aim of this study was to compare the efficacy of the following interventions for the promotion of habitual physical activity, fundamental movement skill proficiency and perceived competence and for reducing adiposity in overweight and obese children: a child-centred physical activity skill-development program (PA), a parent-centred dietary modification program (DIET) and a childcentred physical activity skill-development program plus a parent-centred dietary modification program (PA+DIET). The current study was an assessor-blinded, multi-site, randomised controlled trial. All interventions were delivered over a 6-month treatment period and included a 10-week intensive face-to-face program and a 3-month maintenance phase. Outcome assessments at baseline and 6- and 12-month follow-up included: objectively measured physical activity (total physical activity and percent of time in moderate, vigorous and moderate-to-vigorous physical activity), video-assessed fundamental movement skill proficiency (locomotor skills, object-control skills and gross motor quotient), domainspecific perceived competence (athletic/physical, social/peer acceptance, scholastic/cognitive competence, behavioural conduct, physical appearance and globalself-worth), and adiposity (BMI z-score and waist circumference). Primary analyses were conducted following the intention-to-treat principle using linear mixed models. Of the 165 participating overweight or obese children who completed BMI assessments at baseline, 114 (69%) and 106 (64%) were retained at 6- and 12-month follow-ups, respectively. Study findings indicated that improvements in fundamental movement skill proficiency outcomes were greater in PA and PA+DIET participants than DIET participants at 6-months, though not at 12-months. Despite these changes, perceived athletic/physical competence and habitual physical activity were not found to differ between groups 6- or 12-months after the beginning of treatment. Within-group findings indicated that the PA program influenced children’s perceived competence in the physical activity and social domains, while the DIET program enhanced children’s perceptions of their physical appearance and behavioural conduct. Subsequently, the combined PA+DIET program resulted in within-group improvements in selfperceptions at 6-months and 12-months in all of the domains influenced individually by the physical activity and dietary treatments. All three evaluated treatments were associated with improvements in BMI z-score at 6-months, with maintenance of improvements apparent in all groups at 12-month follow-up. Moreover, both the DIET program and, to a lesser degree, the PA+DIET program were associated with greater reductions in adiposity at 6- and 12-months, compared with the PA group, indicating that these two programs were more efficacious for reducing adiposity in overweight and obese 5- to 9-year-old children. In light of the study findings, the child-centred physical activity skilldevelopment program was considered efficacious for enhancing overweight and obese children’s fundamental movement skill proficiency in the short-term. However, a beneficial effect of treatment to participants’ habitual physical activity could not be established. To enhance the program’s impact on fundamental movement skill proficiency in the long-term, and on perceived athletic/physical competence and habitual physical activity, modifications to the program should be considered, including: i) delivering the program content over a longer treatment period (e.g. 20-weeks) or reducing the content by focusing on the most enjoyable movement skills and those that predict child physical activity behaviour, ii) further parent-centred physical activity treatment sessions, and iii) greater focus on parent-centred behaviour modification strategies for physical activity. Where improvement in a wide range of behavioural, psychological and physiological outcomes is desired, the combined PA+DIET program would be recommended. This program resulted in improvements in overweight and obese children’s movement competency, perceived competence and adiposity in the shortterm and, in some cases, at 12-month follow-up, illustrating its efficacy in the treatment of obesity and related behavioural and psychosocial outcomes in children. As such, effectiveness trials are warranted to examine the transferability of the PA+DIET program in community settings. The promotion of physical activity and the prevention and treatment of obesity in childhood are issues central to the current and future health status of people in many countries, and are therefore issues that warrant further consideration and continued research efforts.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.