Exploring the Mechanisms of Physical Activity and Dietary Behavior Change in the Program X Intervention for Adolescents

Lubans, David R.; Morgan, Philip J.; Callister, Robin; Collins, Clare E.; Plotnikoff, Ronald C.

doi:10.1016/j.jadohealth.2009.12.015

« Previous Next »Journal of Adolescent Health
Volume 47, Issue 1 , Pages 83-91, July 2010

Exploring the Mechanisms of Physical Activity and Dietary Behavior Change in the Program X Intervention for Adolescents

David R. Lubans, Ph.D.
- School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan Campus, Callaghan, Newcastle NSW, Australia
- Address correspondence to: David R. Lubans, Ph.D., University of Newcastle, School of Education, Callaghan Campus, NSW 2308, Australia.
Philip J. Morgan, Ph.D.
- School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan Campus, Callaghan, Newcastle NSW, Australia
Robin Callister, Ph.D.
- School of Biomedical Sciences and Pharmacy, Faculty of Health, University of Newcastle, Callaghan Campus, Callaghan, Newcastle NSW, Australia
Clare E. Collins, Ph.D.
- School of Health Sciences, Faculty of Health, University of Newcastle, Callaghan Campus, Callaghan, Newcastle NSW, Australia
Ronald C. Plotnikoff, Ph.D.
- School of Education, Faculty of Education and Arts, University of Newcastle, Callaghan Campus, Callaghan, Newcastle NSW, Australia
- Faculty of Physical Education and Recreation and School of Public Health, University of Alberta, Edmonton, Canada

Received 18 August 2009; accepted 12 December 2009. published online 11 February 2010.

Purpose

The objective of this investigation was to examine the mechanisms of physical activity and dietary behavior change in the Program X intervention.

Methods

Program X involved a clustered randomized controlled design with six schools (N=124 participants, mean age=14.1±0.8 years) randomized to intervention or control conditions for the 6-month study period. Physical activity and fruit and vegetable consumption were assessed using pedometers and questionnaires, respectively. The theoretical framework of the intervention was assessed using structural equation modeling, mediation, and moderation analyses.

Results

The model explained 56% of the variance in physical activity at 6-months, but did not represent a good fit to the data, χ²=87.43, df=19, p < .001. The model explaining fruit and vegetable consumption explained 31% of the variance and provided a good fit to the data, χ²=12.40, df=10, p=.259. None of the variables satisfied the criteria for mediation or moderation in the physical activity model, but gender moderated the effects of intervention on fruit and vegetable consumption.

Conclusions

None of the hypothesized mediators were responsible for behavior change in the Program X intervention. Future studies should address the limitations of existing psychosocial scales and continue to explore the mechanisms of behavior change using model testing, mediation, and moderation analyses.

Keywords: Mediation, Moderation, Structural equation modelling, Health promotion