Understanding the associations between motivational properties of identity and eating behaviours

Introduction. Identity refers to an individual's unique characteristics, social roles and affiliations, which are proposed to contain motivational features that influence human behaviour. This implies that the motivational aspects of one's identity can influence eating behaviours and, therefore, may be useful in eating behaviour change interventions. The present thesis aims to investigate this proposal through a systematic review and three empirical studies.Methods. The research presented in Chapter Two (Study One; a systematic review) aimed to synthesise and analyse the diverse array of identity, motivation and eating behaviour theories, constructs, and research outcomes in the studies eligible for inclusion. The identity theories and eating behaviours in each study were systematically classified, and study type and quality were assessed using a recognised tool. Study findings were then analysed to enable recommendations to be made about the theories and perspectives that offer the most promise for use in future eating behaviour change interventions. The methods used in the empirical studies are outlined in Chapter Three. In Chapter Four (Study Two), confirmatory factor analysis (CFA) and measurement invariance analysis of two-wave participant data (346 participants) aimed to create a measurement model which can be used to analyse the relationships between identity, motivational self (operationalised as aspirations) and eating behaviours. Using the same sample as Chapter Four, Chapter Five (Study Three) aimed to analyse the relationships in the model using structural equation modelling (SEM) to establish the relationships between factors. Finally, Chapter Six (Study Four), which uses a subset of the sample used in Studies Two and Three (250 participants), aimed to establish the precise associations between factors using multiple linear regression analysis. Results. Chapter Two (Study one) identified that self-determination theory (SDT) and self-schema-based constructs are consistently associated with eating behaviour change. Based on this review, it was also proposed that identity can motivate behaviour both explicitly and indirectly via one's aspirations. As such, identity and an SDT construct (aspirations) were included in the measurement model developed in Chapter Four (Study Two). The measurement invariance analysis in Chapter Four resulted in eight separate invariant measurement models, each with a factor encompassing personal, social and relational aspects of identity, one intrinsic and one extrinsic aspiration factor and one of eight eating behaviour factors (e.g., satiety responsiveness or enjoyment of food). Chapter Five (Study Three) found that food fussiness negatively predicted intrinsic and extrinsic aspirations. In addition, extrinsic aspirations positively predicted satiety responsiveness. Chapter Six (Study Four) identified that food fussiness negatively predicts health aspirations but does not predict image aspirations, and that image aspirations positively predict satiety responsiveness.Discussion. The research in this thesis identified predictive relationships between aspirations and specific eating behaviours. Overall, there may be opportunity to incorporate support and encouragement to develop intrinsically oriented health goals into public health interventions to reduce food fussiness. However, this is dependent on further research clarifying the varied aetiology of food fussiness and ensuring that incorporating this support in eating behaviour interventions is relevant and appropriate. Raising awareness about the potential risks to healthy eating behaviours of pursuing image goals may be effective in reducing unhealthy eating behaviours. Developing interventions that support the pursuit of aspirations, based less on image-focused rewards from others, may also reduce unhealthy eating behaviours. Future research should confirm the findings of this thesis and identify other eating behaviours (in addition to satiety responsiveness) that may be suitable for such interventions.