Based within the Self-Determination Theory (SDT), the overall objective of this thesis was to examine how motivational processes involved in the regulation of eating give rise to different self-regulation strategies in terms of eating quality and quantity, and how the adoption of these strategies influence women’s eating behaviors and life satisfaction over time. This objective was achieved through a series of eight studies, divided into four manuscripts. First, a measure that would allow us to assess healthy and unhealthy eating behaviors based on recent recommendations of Canada’s Food Guide was developed and validated. In Manuscript #1, we validated the Healthy and Unhealthy Eating Behavior Scale (HUEBS) by examining the structure of the scale (Study 1 N = 360; Study 2 N = 711) and by establishing convergent validity through the examination of the relationships between motivational concepts, healthy and unhealthy eating behaviors as measured by the HUEBS, and waist circumference (Study 2 N = 711; Study 3 N = 264). Results supported the factor structure of the scale. It was also demonstrated that as women moved along stages of change for eating regulation, they reported higher levels of self-determined (versus non-self-determined) motivation and a higher consumption of healthy (versus unhealthy) foods. Furthermore, findings showed that healthy eating fully mediated the relationship between self-determined motivation and waist-circumference, and that the relationship between self-determined motivation and healthy eating was moderated by stages of change. Since there was also a need to develop a scale that would allow us to measure planning and self-monitoring strategies in terms of eating quality (i.e., nutrient intake) and quantity (i.e., calories and portion sizes), Manuscript #2 validated the Planning and Self-Monitoring the Quality and Quantity Scale (PMQQS; Study 1 N = 355; Study 2 N = 318). Results supported the 6-factor structure of the scale and demonstrated that strategies related to the quality of eating were more strongly and positively associated with healthy eating and more strongly and negatively associated with unhealthy eating, whereas strategies related to the quantity of eating were more strongly and positively associated with bulimic symptoms and Body Mass Index (BMI). Manuscript #3 then examined if the strategies assessed by the PMQQS provided additional variance to eating behaviors over and above the effects of motivation (Study 1 N = 456) and if the strategies mediated the relationships between motivation and eating, while controlling for BMI (Study 1 N = 456; Study 2 N = 979). Overall, it was found that strategies played a significant role in explaining eating behaviors and that planning and self-monitoring the quality of eating mediated the relationships between autonomous motivation and healthy and unhealthy eating, whereas planning and self-monitoring the quantity of eating mediated the relationship between controlled motivation and bulimic symptoms. Finally, in Manuscript #4, we tested a longitudinal model (N = 230) examining the roles of goals and motivation in the prediction of the strategies and various types of eating and the effects of adopting these behaviors on life satisfaction over a 3-month period. Results revealed that intrinsic goals were positively associated with autonomous motivation whereas extrinsic goals were positively associated with controlled motivation for eating regulation at Time 1 (the baseline), and that autonomous motivation positively predicted quality strategies whereas controlled motivation positively predicted quantity strategies at Time 2 (1 month). Planning and self-monitoring quality then predicted healthy and unhealthy eating behaviors, whereas planning and self-monitoring quantity predicted bulimic symptoms at Time 3 (3 months). Finally, healthy eating was positively associated with life satisfaction, whereas bulimic symptoms was negatively associated with life satisfaction at Time 3. Overall, this thesis increases knowledge on why some women succeed, whereas others fail, to regulate their eating behaviors over time.

This thesis examined how women cope with various types of body-related discrepancies, such as those related to their physical appearance, and their effects on eating behavior. The Hierarchical Action-Based Model of Inconsistency Compensation, an integrative model comprising tenets from the action-based model of dissonance (Harmon-Jones et al., 2009) and Self-Determination Theory (Ryan & Deci, 2017), was used as a guiding framework to understand motivational differences in compensation processes and eating behavior following a body-related discrepancy. This objective was achieved through three studies broken down into two articles. The first study (Article 1; N = 398) used a mixed method cross-sectional design and examined the types of body-related discrepancies women face, their contextual elicitors, and motivational differences in the propensity of experiencing them. Following the recollection of such experiences, the associations between women’s motivation for eating regulation and eating intentions, and the mediating role of dissonance-based processes in these relationships, were examined. Results revealed that women, in general, experience discrepancies related to the appearance and care toward their body. These experiences were often elicited by body exposure (e.g., reflection in the mirror) and occurred in a non-social-evaluative context. Additionally, women with more controlled eating regulation experienced more discrepancies in eating quality and physical activity. Furthermore, results demonstrated that women with more autonomous eating regulation intended to engage in more healthy eating in response to a body-related discrepancy, whereas women with more controlled eating regulation intended to engage in more disordered eating. These distinct pathways were partly explained by differences in self-compassion, and consequently dissonance arousal, and selection of behavioral (versus cognitive) compensation strategies. The second study (Article 2; N = 107) replicated findings from Study 1 by exposing women to a mirror while being instructed to talk about their body in a non-social-evaluative (n = 52) or a social-evaluative (i.e., presence of two female judges; n = 55) context. Dissonance was experimentally manipulated in an additive fashion (i.e., mirror versus mirror and social evaluation) to determine whether motivational differences in dissonance processes and eating behaviors were contingent upon the evaluative nature of the context. Results partly replicated findings in Study 1, such that women with more autonomous eating regulation intended to engage in more healthy eating following mirror exposure (ME), and this relationship was partly explained by engagement in behavior modification strategies, whereas women with more controlled eating regulation intended to engage in more disordered eating following ME. These relationships persisted across ME conditions. Finally, the third study (Article 2; N = 199) used the same paradigm as Study 2 with the additional manipulation of women’s self-related body talk during ME, such that women were instructed to engage in positive/compassionate (social-evaluative n = 47; non-social-evaluative n = 52) or negative (social-evaluative n = 48; non-social-evaluative n = 52) body talk. This allowed us to observe the effects of positive and negative body talk on women’s eating behaviors and the moderating role of motivation following ME. Results demonstrated that women with more controlled eating regulation benefitted from counter-attitudinal (positive/compassionate) body talk during ME as indicated by more intent to engage in healthy eating behavior. Taken together, results suggest that increased salience of body-related discrepancies negatively affects women’s ability to regulate their eating if they do so for more controlled reasons. This is partly attributed to low emotion regulation resources and use of avoidant compensation strategies. However, these negative implications on their eating behavior can be alleviated via dissonance by facilitating the restructuring of body-related cognitions in contexts that typically elicit body-related discrepancies.