Childhood Obesity
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University of Canterbury Measuring the exposure to Obesogenic Environments among New Zealand School Children A Thesis Submitted in fulfilment of the requirements for a Degree of Master of Science in Geography Andreas Ian Wilson 1-1-2015 Page | ii Page | iii Abstract The prevalence of obesity has increased greatly in the last 30 years. Intensified urban landscapes have created environments that facilitate rising obesity rates. The level of unhealthy food consumption and physical activity accessibility has become imbalanced within the built and social environments of individuals. The term obesogenic environment has been used to describe the increased exposure to obesity, based on the characteristics of the surrounding environment. Previous academic literature has attempted to measure the contribution of obesogenic environment exposure to obesity health outcomes. The key aim of this research is to measure the correlation between obesogenic environments and BMI outcomes of New Zealand school children aged 5-14. Part 1 of this research method considered all children aged 5-14 sampled in the New Zealand Health Survey (NZHS) 2013/2014. Linear regression analysis was used to determine the correlation between BMI and selected NZHS participant responses; the key analysis in part 1 was the correlation between BMI and participants mode of transport to and from school. Part 2 of this research method focused on the New Zealand city of Hamilton. The research method used NZHS data to measure participant exposure to obesogenic environments based on the health responses given by participants. Geospatial network analysis was used to determine the NZHS participant’s home, route and school environments. Obesogenic environment exposure was defined by the Hamilton food and physical environment attributes contained within euclidean buffer zones created around the participant’s home, route and school environment. Linear regression analysis was then used to determine the geospatial correlation between the participant’s environment exposure and BMI outcomes. The results of this research method suggest that participant’s exposure to obesogenic environments did not contribute to obesity health outcomes, based on the lack of statistical evidence provided by the linear regression analysis. Page | iv Table of Contents Abstract….. ................................................................................................................................................. iv Table of Contents ........................................................................................................................................ v Figures…….. ............................................................................................................................................. viii Tables……. ................................................................................................................................................. ix List of abbreviations ................................................................................................................................... x Acknowledgements .................................................................................................................................... xi Chapter 1 – Introduction ............................................................................................................................ 1 1.2 Obesogenic environments ............................................................................................................. 2 1.3 Obesity in New Zealand ................................................................................................................ 2 1.4 Research Purpose .......................................................................................................................... 3 1.2 Research Aims and Objectives ..................................................................................................... 4 1.3 Thesis Structure ............................................................................................................................ 5 Chapter 2- childhood obesity ..................................................................................................................... 7 2.1 Chapter Summary ......................................................................................................................... 7 2.2 Introduction ................................................................................................................................... 7 2.3 Health Related Consequences ....................................................................................................... 9 2.4 Body Mass Index measurement .................................................................................................. 11 2.5 Cost of Childhood Obesity .......................................................................................................... 14 2.6 Obesity and Public Health Intervention ...................................................................................... 16 2.6.1 Build Environment Intervention ......................................................................................... 17 2.6.2 Social Environment Intervention ........................................................................................ 17 Summary ................................................................................................................................................. 18 Chapter 3 – Obesogenic Environments ................................................................................................... 20 3.1 Obesity and Inequality ................................................................................................................ 21 3.2 Defining Obesogenic Environments ........................................................................................... 23 3.3 Food Environment vs Physical Environment .............................................................................. 24 3.2.1 Food Environment............................................................................................................... 24 3.2.2 Physical Environment ......................................................................................................... 28 Page | v 3.4 Mapping Obesogenic Environments ........................................................................................... 33 3.4 Measuring the obesogenic environment .............................................................................. 34 Summary ................................................................................................................................................. 38 Chapter 4 – Childhood Obesity in New Zealand.................................................................................... 39 Chapter Summary ................................................................................................................................... 39 4.1 Introduction ................................................................................................................................ 40 4.1.1 Age ...................................................................................................................................... 43 4.1.2 Ethnicity .............................................................................................................................. 45 4.1.3 Social Deprivation............................................................................................................... 46 4.2 Obesity Response in New Zealand ............................................................................................. 48 4.3 Hamilton City .............................................................................................................................. 53 4.4 Summary ..................................................................................................................................... 54 Chapter 5 – Method .................................................................................................................................. 55 Summary ................................................................................................................................................. 55 5.2 Data Sources ............................................................................................................................... 56 5.2.1 NZ Health Survey ............................................................................................................... 56 5.2.2 Control Variables ................................................................................................................ 57 5.2.3 Participant Privacy and Safety ................................................................................................ 59 5.2.4 Otago Social Deprivation Index .......................................................................................... 60 5.3 Part 1: Nationwide Analysis ....................................................................................................... 62 5.3.1 BMI vs Mode of Transport ................................................................................................. 63 5.4 Part 2: Hamilton Geospatial Analysis ......................................................................................... 64 5.4.1 Creating the Obesogenic Environment ..............................................................................