- 1 - Biopsychological Investigation of Hedonic Processes in Individuals Susceptible to Overeating: Role of Liking and Wanting in Trait Binge Eating Michelle Dalton Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds Institute of Psychological Sciences July 2013 - 2 - The candidate confirms that the work submitted is her own, except where work which has formed part of jointly authored publications has been included. The contribution of the candidate and the other authors to this work has been explicitly indicated below. The candidate confirms that appropriate credit has been given within the thesis where reference has been made to the work of others. Chapter 2 of this thesis was based in part on the jointly-authored publication: Dalton, M., King, N.A., & Finlayson, G., (2013) Appetite, Satiety and Food Reward in Obese Subjects: A Phenotypic Approach, Current Nutrition Reports, 1-9. Chapter 7 of this thesis was based in part on the jointly-authored publication: Dalton, M., Blundell, J. & Finlayson, G. (2013) Effect of BMI and binge eating on food reward and energy intake: further evidence for a binge eating subtype of obesity. Obesity Facts, 6; 348-359. Chapter 8 of this thesis was based in part on the jointly-authored publication: Dalton, M., Blundell, J. & Finlayson, G. (2013) Examination of obese binge-eating subtypes on reward, food choice and energy intake under laboratory and free-living conditions. Frontiers in Psychology, 4, 757. The candidate confirms that her contribution was primarily intellectual and she took a primary role in the production of the substance and writing of each of the above. Her co-authors confirm that their contribution to each of the articles was in guiding the research presented and its evaluation as well as editing drafts of the manuscripts. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. © 2013 The University of Leeds and Michelle Dalton - i - Acknowledgements 1 Acknowledgements Firstly, I would like to sincerely thank Dr. Graham Finlayson, who has mentored me as an undergraduate student and throughout my post-graduate work as my PhD supervisor, for his encouragement and support over the last six years. His enthusiasm for research is contagious and it was doing a summer internship with him that initially inspired me to do a PhD. Without his guidance, expertise, and dedication this thesis would not have been possible. I would also like to thank my second PhD supervisor, Professor John Blundell, whose expertise, enthusiasm and drive for excellence has been inspiring. Under the guidance of John and Graham I have been fortunate to gain invaluable skills in scientific design and analysis, writing manuscripts and presentation delivery. I am sincerely grateful for all of the opportunities they have provided to me and I could not have wished for better supervisors. I would like to acknowledge the Biotechnology and Biological Sciences Research Council: Diet and Health Research Industry Club (grant number #BB/G530141/1), for providing the funding that enabled me to undertake my postgraduate work. I am grateful to Dr. Joanne Cecil and Dr. Roger Tavendale for sharing with me their expertise and for making me feel welcome during my visit to St. Andrews and Dundee, and for their contribution to Chapter 9. I would also like to acknowledge those people who contributed to this work. I thank Maddy Kavanagh and Olivia Bailey for their assistance in conducting the study in Chapters 5 and 6 and Rachel Fenwick and Alice Wright for their assistance in conducting the study in Chapter 9. Furthermore, I would like to thank the members of the HARU for providing help whenever it was required. I am also grateful to my parents for their unwavering belief and support throughout my life, and to my friends, in particular Kirstie and Lucy, who have listened and provided me with endless support, encouragement and happiness. Last but not least, I would like to thank my husband, James, for reading every last word and for making sure that we celebrated the little things…with champagne…and cake. - ii - Abstract 2 Abstract The objective of this thesis was to identify and characterise a robust phenotype susceptible to reward-driven overeating. Specifically, the thesis aimed to examine the role of liking and wanting for food in trait binge eating and to determine other potential biopsychological markers of susceptibility (psychological, physiological and genetic). In a systematic series of studies, normal-weight (Ch.6,7,9) and overweight or obese (Ch.7,8) females were categorised as either ‘binge-type’ or ‘non-binge type’ based on their scores on the Binge Eating Scale. Using a biopsychological approach, susceptibility was characterised across several different scientific domains. Liking and wanting for food were measured using the validated Leeds Food Preference Questionnaire (Ch.5-9) – LFPQ - which separated explicit and implicit processes. Food choice and energy intake were assessed objectively and quantitatively in the laboratory using ad libitum test meals (Ch.5-9) and under free-living conditions using a validated multiple-pass 24-hour dietary recall (Ch.8). Physiological markers (fat mass, fat-free mass) were measured using bioelectrical impedance and air plethysmography (Ch.6-9). Potential genetic markers of susceptibility (e.g. FTO, DRD2, Taq1A, CD36) and intermediary phenotypes of trait binge eating were examined using a candidate gene approach (Ch.9). Overweight-obese ‘binge-types’ had enhanced explicit liking for food overall, and greater implicit wanting for high-fat sweet foods compared to overweight-obese ‘non-binge types’. This was associated with an increased preference for, and consumption of these foods under laboratory and free-living conditions. Furthermore, obese ‘binge-types’ had greater levels of adiposity and reported greater food cravings and lower positive affect. Lean ‘binge-types’ had a greater implicit wanting for sweet foods, and exhibited a greater preference for these foods. Liking - iii - and wanting for food assessed by the LFPQ were related to energy intake and food choice. Notably, an enhanced liking for food in a fed state was associated with greater energy intake. In addition, implicit wanting emerged as an important process; while enhanced implicit wanting for sweet foods was a risk factor for overeating, greater implicit wanting for low-fat savoury foods appeared to be protective. Examination of the intermediary phenotypes revealed that variation in certain genes relating to reward, taste and obesity were associated with energy intake and food choice, body composition and food hedonics. This thesis has identified a distinct, ecologically valid, behavioural phenotype of obesity that is characterised by reliable psychological and physiological characteristics. Furthermore, the results confirm the value of distinguishing between liking and wanting for food and for studying their role in eating behaviour. - iv - Publications and presentations 3 Publications and presentations Publications Research Articles Dalton, M., Blundell, J. & Finlayson, G. (2013) Examination of obese binge-eating subtypes on reward, food choice and energy intake under laboratory and free-living conditions. Frontiers in Psychology, 4, 757. Dalton, M., Blundell, J. & Finlayson, G. (2013) Effect of BMI and binge eating on food reward and energy intake: further evidence for a binge eating subtype of obesity. Obesity Facts, 6; 348-359 Finlayson, G., Arlotti, A., Dalton, M., King, N.A. & Blundell, J.E. (2011). Implicit wanting and explicit liking are markers for trait binge eating. A susceptible phenotype for overeating. Appetite, 57; 722-728 Reviews Dalton, M., King, N.A., & Finlayson, G., (2013) Appetite, Satiety and Food Reward in Obese Subjects: A Phenotypic Approach, Current Nutrition Reports, 1-9 Cecil, J.E., Dalton, M., Finlayson, G., Blundell, J., Hetherington, M. & Palmer, C. (2012) Obesity and eating behaviour in children and adolescents: contribution of common gene polymorphisms. International review of Psychiatry, 24 (3); 200-210 Finlayson, G. & Dalton, M. (2012) Hedonics of Food Consumption: Are Food ‘Liking’ and ‘Wanting’ viable targets for appetite control in the Obese? Current Obesity Reports, 1; 42-49. Finlayson, G. & Dalton, M. (2012) Current progress in the assessment of ‘liking’ vs. ‘wanting’ for food in human appetite. Comment on ‘“You Say it’s Liking, I Say it’s Wanting…” On the difficulty of disentangling food reward in man’ Appetite, 58 (1), 373-378 Book chapters Dalton, M. & Finlayson, G. (Oct 2013) Hedonics, satiation and satiety. In Satiation, Satiety and the Control of Food Intake Blundell, J., Dalton, M & Finlayson, G. (2013) Appetite and Satiety – A Psychobiological Approach. In Murcott, A., Belasco, W. & Jackson, P. The Handbook of Food Research. Bloomsbury Academic Finlayson, G., Dalton, M. & Blundell J. (2012) Liking vs. Wanting Food in Human Appetite: Relation to Craving, Overconsumption and “Food Addiction”. In Brownell, K.D. & Gold, M.S. Food and Addiction: A Comprehensive Handbook. Oxford University Press. - v - Oral and poster presentations Oral presentations Is trait binge eating a hedonic subtype of obesity? 48hr free-living and laboratory- based examination of reward, food selection and energy intake. Paper presented at Society for the Study of Ingestive Behavior, New Orleans, USA, July 2013 Characterising trait