Protection, risk and dieting: Intermittent fasting diets and disordered eating Jasmin Langdon-Daly D.Clin.Psy. Thesis (Volume 1) 2016 University College London UCL Doctorate in Clinical Psychology Thesis declaration form I confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. Signature: Name: Jasmin Langdon-Daly Date: 09.06.16 2 Overview Consideration of factors and behaviours which may increase the risk of disordered eating, or protect against these difficulties and promote resilience, can inform efforts to prevent and intervene. Part One of this thesis is a systematic review of research into protective factors against eating disorders and disordered eating in proximal social systems. A range of potential protective factors in families, schools, peer groups and neighbourhoods are identified. Many of these factors may be non-specific to eating difficulties, promoting a range of positive outcomes, while others may be more specific to disordered eating. Methodological issues in the literature which limit the ability to draw firm conclusions are discussed. Part Two presents empirical research into the impact of intermittent fasting (IF) diets on eating psychopathology, binge eating, food craving and mood. Contrary to expectation, starting a 5:2 IF diet did not result in increases in disordered eating or binge eating in healthy adult dieters, and in fact appeared to result in improvements in all outcomes. Higher scores on measures of risk factors for eating disorders at baseline were associated with greater reductions in disordered and binge-eating over the 28 day IF period. Limitations to interpretation of results are considered, along with potential clinical applications and suggestions for further research. Part Three presents a critical appraisal of the literature review and empirical paper. Assumptions informing the research questions, aspects of the research process, and potential interpretations and implications of the findings are considered, with reference to the perspective of the scientist practitioner. The empirical research in Part Two was completed as part of a joint research project. The details of the other part of this project can be found in Mahony, K. (2016). Nutrition and cognition: Exploring their relationship from two sides of the same coin. Clinical Psychology Doctorate Thesis. 3 Table of Contents Thesis Declaration Form ................................................................................ ................ 2 Overview .................................................................................................. 3 Table of Contents .................................................................................................. 4 List of Tables .................................................................................................. 5 List of Figures .................................................................................................. 5 Acknowledgements .................................................................................................. 6 Part 1: Literature Review .................................................................................................. 7 Abstract .................................................................................................. 8 Introduction .................................................................................................. 9 Methods .................................................................................................. 13 Results .................................................................................................. 15 Discussion .................................................................................................. 41 References .................................................................................................. 51 Part 2: Empirical Paper .................................................................................................. 56 Abstract .................................................................................................. 57 Introduction .................................................................................................. 58 Methods ................................................................................................... 63 Results ................................................................................................... 71 Discussion ................................................................................................... 80 References ................................................................................................... 87 Part 3: Critical Appraisal ................................................................................................... 91 References ................................................................................................... 100 Appendices ................................................................................................... 102 Appendix A ................................................................................................... 103 Appendix B ................................................................................................... 107 Appendix C ................................................................................................... 108 4 Appendix D ................................................................................................... 109 Appendix E ................................................................................................... 116 Appendix F ................................................................................................... 117 Appendix G ................................................................................................... 118 List of Tables Part 1: Literature Review Table 1 Standardised measures of disordered eating used in studies 18 Table 2 Participant, sample, design, outcome measures, QualSyst score and key findings for all studies 20 Part 2: Empirical Paper Table 1 Baseline scores on outcome and risk factor variables for study completers and non-completers 72 Table 2 Correlations between outcome and risk factor variables at baseline, for participants completing the study 74 Table 3 Mean calorie intake and proportion of energy intake from carbohydrates and protein for two days pre-diet, non-fasting days, and fasting days 75 Table 4 Change in eating pathology, binge-eating, food craving and mood after 28 days of 5:2 IF 76 Table 5 Main effects of and interactions with risk factor variables 79 List of Figures Part 1: Literature Review Figure 1 Diagram of systematic search protocol with studies excluded at each stage 16 Part 2: Empirical Paper Figure 1 Participant numbers and attrition at each stage 71 5 Acknowledgements I would like to thank my supervisors, Dr Lucy Serpell and Dr Sam Gilbert, for their invaluable knowledge, guidance, feedback and support, without which this thesis would not have got very far. I am also hugely appreciative of my research partner, Kate Mahony. Our collaboration has helped to keep me smiling throughout the research process, and I have been able to achieve far more than expected with her working alongside. Throughout the project I have received help from many different people. I am grateful to Amber Chung, Research Assistant, for her help in processing data for the empirical paper. Thank you to the organisations and individuals who helped by posting and sharing our advertisements for participants, in particular The Fast Diet website, and to our participants themselves, for their interest and enthusiasm. Finally, I would like to express my gratitude to my husband, family, friends and coursemates, for all of their support. 6 Part 1: Literature Review Systems of protection: Protective factors against disordered eating in the proximal social environment 7 Abstract Aims: This review aims to identify and evaluate the literature investigating protective factors and eating disorders, to establish what is known about factors in proximal social systems (family, peer group, school and neighbourhood) that could be considered protective against the development of eating disorders/ eating pathology. Methods: A systematic review of the literature was conducted on five databases, using search terms related to eating disorders/disordered eating and protective factors. Studies were systematically screened for inclusion, and all included studies were evaluated for study quality. Results: Thirty-three studies met criteria for inclusion. The majority of studies looked at factors within families, including aspects of family relationships and family practices around food or eating. There was a particular research focus on the potential protective role of regular family meals. Potential protective factors also appear to exist at the level of schools, peer groups and neighbourhoods/communities. There were weaknesses in the methodology used in many studies, in particular an over-reliance on cross-sectional correlational methods. Conclusions: Many of the potential protective factors identified, such as social support and family connectedness, may be non-specific to eating difficulties, promoting general adaptive development and a range of positive development outcomes. Factors in the family environment around food, eating and weight, such as frequent family meals and avoiding comments about weight, may be more