Exploring adolescent food choice: A food environment perspective Rachel Louise Tyrrell BSc Honours ANutr Thesis submitted for the degree of Doctor of Philosophy May 2014 Human Nutrition Research Centre Institute of Health & Society Faculty of Medical Sciences Newcastle University Abstract Obesity is a significant problem in young people. Relative to other age groups, less is known about health related lifestyle behaviours of young people, particularly in the transition period from adolescence to adulthood. Food choices are made within the food environment, which encompasses any opportunity to obtain food or influence food choice. Environmental exposures such as the availability and accessibility of ‘more healthy’ and ‘less healthy’ food options interact with individual factors to drive food choice. The aim of this work was to explore whether, and to what extent, the food envionment to which a young person is exposed has an influence on individual dietary intake. A range of methods including food diaries in conjunction with text messaging and photography, questionnaires, Global Positioning Systems (GPS), Geographical Information Systems (GIS), and qualitative interviews were used. The majority of young people (96%) reported using a food outlet at least once over a 4-day period. Less healthy food outlets, such as takeaways and convenience stores, were the most frequently used. Being exposed to a greater number of food outlets was significantly associated with visiting a greater number of food outlets. Similarly, being exposed to a greater proportion of ‘less healthy’ food outlets was associated with visiting a greater proportion of ‘less healthy’ food outlets. However, relationships between the number of food outlets visited and dietary intake were weak and there was little evidence to suggest an association between exposure to food outlets and dietary intake. Qualitative results indicated that time, geographic location, economic cost and social occasion influenced choice of food outlet. In addition, the particular food outlet chosen appeared to dictate the food choices made with habitual repeat ordering of meals an emerging theme. No previous research has linked individual eating behaviour to the food environment. Identifying the types of outlets young people use, the food choices made within and the factors influencing decisions and behaviours is important for the development of targeted long term obesity prevention strategies to facilitate healthier food outlet environments. i Dedication In loving memory of two very special people taken from us far too soon. James Wilton, 2nd October 1981 – 2nd February 2014 Roy Smith, 2nd August 1954 – 21st April 2014 Forever in our hearts. ii Acknowledgements The research presented within this thesis was funded by the Food Standards Agency's Postgraduate Scholarship Scheme. I have a lot of people to thank but firstly I'd like to thank the participants without whom this research could never have happened. You were all a delight to work with and I appreciate the time and effort each of you put into the study. A big thank you to my supervisory team: Prof Ashley Adamson, Dr Amelia Lake, Dr Susan Hodgson and Dr Wendy Wills. Your support and encouragement over the past four years has been invaluable. Thanks to Prof John Mathers and Dr Mary Brennan for their advice and reassurance during annual progress meetings. Huge thanks to all my colleagues at the HNRC for making the office a fun place to be and for keeping me going on a day-to-day basis. Special thanks to my fellow PhD students, especially Rachel ‘let’s go for sushi’ Gallo, Suzanne ‘is it chocolate time?’ Spence, Jo ‘pass the Krupnik’ Gorniak, and Lorraine ‘shall we open a tea shop?’ McSweeney. Thanks also to #teamalcohol for being incredibly supportive over the last 7 months of writing up - you guys are the best! Thanks and apologies to my wonderful family and friends. I know I’ve been more than a little neglectful and promise I’ll see you all lots more from now on! Last, but certainly not least, the biggest thank you to Dave Smith for keeping me grounded and always asking the most important question; “What would Valentino do?” iii Statement of Contributions to Research A number of people, including undergraduate placement students and fellow PhD students, contributed the data collection and entry at various stages of the study. All were trained and supervised by Rachel Tyrrell. Gillian Hodge and Abigail Coleman were placement students in HNRC during 2010/11 and assisted with pilot study data collection (food diaries and anthropometric measurements) and data entry under supervision. Lisa Burn was a placement student in HNRC during 2011/12 and assisted with food diary and anthropometric data collection during the main phase of the study. She completed questionnaire and food diary data entry and coding, and transcribed five of the qualitative interviews, under supervision. Victoria Cox was supervised by Rachel Tyrrell when completing her undergraduate dissertation project during 2011/12. Victoria was trained to complete Measuring Food Environments surveys. The results from these surveys (n=30) were included in the final analysis. Paul Adamson built the Food Environment Access database used for dietary analysis. Wendy Wills read the qualitative interview transcripts and provided a second option regarding the qualitative analysis coding frame. Catherine Purvis-Mawson reviewed documents for suitability for use with young people, assisted with pilot study recruitment and provided contact details for youth workers during recruitment for the main study. Special thanks to the following individuals: to all the teachers, youth workers and others who helped with recruitment, particularly Rhonda Knox and Catherine McCullagh. To Tom Burgoine, Louis Goffe and Rachel Gallo for their help and support with GIS matters. To Lisa Burn, Rachel Gallo, Lorraine McSweeney, and Sue Bell for giving up their time to ensure security protocol was adhered to when conducting data collection and interviews with young people outside of office hours. iv Table of Contents Chapter 1 Introduction ...................................................................................... 1 Chapter 2 Review of the literature .................................................................... 4 2.1 Literature review approach .................................................................... 4 2.2 Introduction ............................................................................................ 5 2.3 The obesogenic environment ................................................................. 7 2.3.1 Defining the food environment .......................................................... 9 2.4 Exposure food environment ................................................................. 13 2.4.1 Identifying food outlet locations ....................................................... 13 2.4.2 Classification of food outlets by type ............................................... 15 2.4.3 Measures of exposure to food outlets ............................................. 16 2.4.4 The relationship between exposure to food outlets and health outcomes .................................................................................................... 20 2.4.5 Using Global Positioning System and travel routes to investigate exposure to food outlets ............................................................................. 25 2.5 Visited food environment ..................................................................... 27 2.5.1 Organisational food environment .................................................... 28 2.5.2 Visited community food outlet environment ..................................... 34 2.5.3 Frequency of eating at food outlets and health outcomes ............... 37 2.5.4 Consumer food environment ........................................................... 39 2.5.5 Consumer food environment and health outcomes ......................... 40 2.6 Individual food environment ................................................................. 44 2.6.1 Measuring health related outcomes in adolescents ........................ 45 v 2.6.2 Psychosocial factors influencing adolescent food choice ................ 50 2.6.3 Socio-demographic factors influencing food choice ........................ 54 2.7 Literature review summary ................................................................... 56 2.8 Research aims and objectives ............................................................. 57 2.9 Methodology ........................................................................................ 58 Chapter 3 Methods development .................................................................... 59 3.1 Acceptability of methods ...................................................................... 61 3.2 Lifestyle Questionnaire development ................................................... 63 3.3 Questionnaire database development ................................................. 63 3.4 Global Positioning System device testing and selection ...................... 64 3.5 Pilot study ............................................................................................ 65 3.5.1 Ethical approval and incentives ....................................................... 65 3.5.2 Study sample .................................................................................. 65 3.5.3 Pilot study timeline .........................................................................