Assessments of the role of self-control in determining an individual's eating behaviour in different eating scenarios
Obesity is an increasing global problem. Although the causes of this condition comprise diverse factors, it is argued that a key contributor is the contemporary food environment. The current food environment constantly exposes individuals to an abundance of food-related signals or ‘cues’ that encourage consumption. There is a growing body of literature that endeavours to understand individual differences in terms of how people respond to these food cues. Interestingly, research shows that some individuals are more susceptible to the effects of the current food environment than others. One of the key hypotheses to explain such individual differences relates to self-control. While previous research affirms self-control is crucial for keeping homeostatic balance, it remains unknown how self-control moderates energy intake and its primary determinants – portion size and energy density. Thus, the aim of the current doctoral research is to systematically test for the role of self-control in determining individuals’ eating behaviour. Specifically, the thesis discusses the role of self-control in influencing an individual’s food choice, energy intake, portion size and energy density, in different eating scenarios. In addition, the thesis investigates the possibility of a cognitive training paradigm on moderating an individual’s self-control for food choice. In this thesis, Study 1 tested the consistency across three measures of self-control, that are available in the literature, for predicting an individual’s food choices. A total of 116 female participants were tested with the inhibitory control test, an implicit self-control task, and an explicit self-control task, and then these measures were then analysed against each participant’s performance on a food choice task. Results from this study revealed that the explicit self-control measure (i.e. Tangney’s Brief Self-Control Scale) was the most effective approach for predicting food choice (for a high-calorie food) relative to the other two measures (p = 0.002). In addition, no statistical relationship was observed between the three self-control measures (p > 0.05), suggesting they measure distinct self-control processes. Study 2 assessed the role of self-control energy intake across diverse food categories (i.e., sweet snack, savoury snack and main meal). A total of 61 female participants, identified as having either high or low self-control (i.e. Tangney’s Brief Self-Control Scale), were tested for their eating behaviour for the above-mentioned three categories of food. Results from this study showed that self-control by this measure had no direct effect on energy intake across the three food categories (p > 0.05). Nevertheless, the results revealed that self-control can moderate the energy intake of a certain food category (i.e., sweet snack: p = 0.048; savoury snack: p < 0.001). This study suggested that the moderating role of self-control on energy intake differed across food categories (found in both sweet and savoury snack, but not in main meal scenario). Study 3 tested the specific effect of self-control on the two primary determinants of energy intake – portion size and energy density. A total of 44 female participants, identified as having either high or low food self-control (i.e. Food Self-Control Scale), were tested with two high and low-calorie foods in both food choice and consumption tasks. Results from the study revealed that self-control only exerted effects on an individual’s food choice based on energy density (p < 0.05), but not on portion size (p > 0.05). This new finding provided useful insights into the subsequent development of a self-control intervention strategy, which was described in study 4. Study 4 developed a cognitive training paradigm for self-control and tested its effectiveness on influencing both portion size and energy density judgements for individuals with low self-control (i.e. Food Self-Control Scale). The training paradigm was constructed based on a modified implicit association test in conjunction with body images. Results showed that individuals who underwent the training programme had no significant reduction in their portion size nor energy density intake compared to the baseline session (p > 0.05). This study indicated that simple cognitive training cannot moderate the effects of self-control on dietary decision-making. Overall, this doctoral research assessed the role of self-control in determining an individual’s eating behaviour in different eating scenarios. Findings from this project indicated self-control, as a top-down self-control trait, was associated with choices of food energy density, it however did not directly influence portion size. The moderating role of self-control on food choice and energy intake differed across eating scenarios (e.g., present in both sweet and savoury snack consumption, but not in main meal consumption). Overall, this research provided important and novel insights into the role of self-control in regulating eating behaviour via food energy density.
Advisor: Mei, Peng; Miranda, Mirosa; Indrawati, Oey
Degree Name: Doctor of Philosophy
Degree Discipline: Department of Food Science
Publisher: University of Otago
Keywords: self-control; food choice; portion size; energy density; energy intake; eating behaviour.
Research Type: Thesis