Exploring Novel Associations Between Psychosocial Work Factors, Obesity, and Energy Balance-Related Behaviours

Abstract

In many parts of the world, including Australia, the majority of the adult population is overweight or obese – presenting a significant risk to health and wellbeing. The positive energy balance hypothesis states excess weight is caused by consuming greater dietary energy than is required for functioning and physical activity. While this hypothesis describes the main biological mechanism for weight gain, it does not explain why individuals engage in excess dietary intake and/or insufficient physical activity. The biopsychosocial model advocates the additional consideration of psychological and social factors within various settings. The aim of this research was to provide a better understanding of how psychosocial work factors may be associated with overweight and obesity, as well as two important energy balance-related behaviours: leisure-time physical activity (LTPA) and habitual diet. The Job Demand-Control-Support (JDCS) model is most prevalent in the study of psychosocial work factors, yet there is considerable inconsistency in how it has been operationalised. Previous research suggested equivocal associations between psychosocial work factors and obesity – with some studies reporting associations and others not. Concomitantly, evidence emerged to suggest the two subscales of job control (skill discretion and decision authority) may hold differential associations with some health outcomes, but no previous research had considered the potential for these to hold differential associations with obesity. In study one, cross-sectional analyses of data from 450 South Australian employees revealed the two subscales of job control were the only components of the JDCS model associated with measures of obesity. Notably, these associations were in opposite directions. Higher levels of skill discretion were associated with reduced waist circumference and body mass index (BMI), while higher levels of decision authority were associated with elevated waist circumference. It was important to consider the behaviours that may underpin these associations. Study two comprised a systematic review of studies that consider the associations of LTPA and/or habitual diet with psychosocial work factors within the JDCS model. After screening records (n = 6,863), 31 studies meeting inclusion criteria were summarised. There was general support for a negative association between various conceptualisations of work stress within the JDCS model and LTPA; particularly lower job control and lower LTPA. There was some suggestion of an association between work stress and poorer diet, but insufficient studies to draw strong conclusions. Study two revealed no previous studies had considered the potential for the two subscales of job control to hold unique associations with LTPA or diet. As such, study three employed a similar methodology to study one, but with LTPA (3 categories: no activity, activity but not sufficient, sufficient activity) and dietary energy intake (kJ/day) as the outcomes. Analyses suggested higher levels of skill discretion were associated with increased LTPA, but not associated with diet. Conversely, decision authority was not related to LTPA, but higher levels of decision authority were associated with reduced dietary energy intake. Surprisingly, higher coworker support was associated with increased dietary energy intake. The findings of this thesis suggest the two subscales of job control may be uniquely associated with obesity and energy balance-related behaviours. As such, future research should consider operationalising the JDCS model at the subscale level, since this may reveal novel associations with obesity and other health outcomes – presenting new opportunities to improve employee health and wellbeing. Further implications of this research, as well as limitations and recommendations for future research, including the need for replication, are discussed in the final chapter.