Title

The influence of individual, behavioural and environmental factors on BMI at 6, 8, 10 and 14 years

Abstract

As a child matures from birth to adolescence, the relative influence of individual, behavioural and environmental obesogenic factors varies. In this paper, we report four structural equation models that identify possible causal pathways and interrelationships between key obesogenic factors in the Western Australian Pregnancy Cohort (Raine) Study at age 6, 8, 10 and 14 years.

A sample of 1403 participants (674 females and 729 males) was available for analysis. Data for BMI, physical fitness and activity, sedentary behaviour, socioeconomic status, motor competence, diet, self concept, and the school environment were used to develop exploratory structural equation models (AMOS, SPSS) at 6, 8, 10 and 14 years.

The interrelationships between physical activity and sedentary behaviours changed across models at 6 years (χ2 (df = 22) = 25.036, p = .295), 8 years (χ2 (df = 32) = 33.326, p = .403), 10 years (χ2 (df = 40) = 47.820, p = .185) and 14 years (χ2 (df = 57) = 59.487, p = .385), with motor competence becoming important at adolescence.

The relationship between screen time and physical activity as predictors of BMI was complex, and changed between 6, 8, and 10 years. By 14 years of age motor competency, aerobic fitness and physical activity were highly interrelated and together predicted BMI. These exploratory analyses also identified that diet, the school environment, self-concept, and the valuing of physical activity were not important for BMI. Significant differences in pathways were also found between males and females. For example, the pathway between income and screen time was significant for males, but not females at age 14 years.

Interrelationships among obesogenic factors are complex, dynamic and individualised. Their influence on BMI operates in both direct and indirect ways and changes with age between 6 and 14 years. Interventions for obesity must consider age and gender specific differences in pathways and mechanisms.

Chivers, P., Hands, B., Parker, H., & Bulsara, M. (2010). The influence of individual, behavioural and environmental factors on BMI at 6, 8, 10 and 14 years. Obesity Research and Clinical Practice, 4(S1), S41. doi: 10.1016/j.orcp.2010.09.084

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