We examine the association between living in an urban area with more or less green space and the probability of being obese. This work involves the creation of a new dataset which combines geo-coded data at the individual level from the Irish Longitudinal Study on Ageing with green space data from the European Urban Atlas 2012. We find evidence suggestive of a u-shaped relationship between green space in urban areas and obesity; those living in areas with the lowest and highest shares of green space within a 1.6 km buffer zone have a higher probability of being classified as obese (BMI ⩾ ۳۰). The unexpected result that persons in areas with both the lowest and highest shares of green space have a higher probability of being obese than those in areas with intermediate shares, suggests that other characteristics of urban areas may be mediating this relationship.

Introduction

Over half of the world’s population (54%) currently lives in urban areas (UN, 2015). Growing urbanisation is set to continue with a projected two-thirds of the global population expected to reside in urban areas by 2050 (UN, 2015). Given the worldwide trend of urbanisation, there has been renewed focus on the physical health impacts of living within these urban areas, and in particular the importance of ensuring adequate green space provision. Indeed the United Nations Sustainable Development Goal 11.7 states a target of providing “…universal access to safe, inclusive and accessible, green and public spaces, in particular for women and children, older persons and persons with disabilities” by 2030. The benefits arising from green spaces can be examined from a multitude of angles e.g. mitigation of the urban heat island effect, promotion of local ecosystems, improved air quality and, health and wellbeing effects (see Carlin, Cormican, and Gormally (2016) for full review). This paper focuses on the physical health benefits of green space; in particular whether the presence of green space in urban areas has the potential to reduce an individual’s probability of being obese. The WHO estimates that the prevalence of obesity has more than doubled worldwide between 1980 and 2014 (WHO, 2016), with 1.9 billion adults classified as overweight in 2014, and of these, 600 million classified as obese. This is particularly concerning given that obesity substantially increases the risk of developing other noncommunicable diseases such as cardiovascular disease, diabetes, osteoarthritis and some cancers (WHO, 2016). The primary cause of obesity is an energy imbalance between calories consumed and calories expended (WHO, 2016). This imbalance is the result of increased consumption of highenergy foods and decreased physical activity. Obesity can therefore be considered a side effect of increased urbanisation, which has led to a rise in sedentary life-style patterns. Coined by Swinburn, Egger, and Raza (1999), the term obesogenic environment refers to “the sum of influences that the surroundings, opportunities, or conditions of life have on promoting obesity in individuals or populations”. This definition which recognises the importance of an individual’s social, economic and physical environment, shifts the focus of solving the obesity epidemic from the individual to the systemic level. As identified by Mackenbach et al. (2014), several features of the physical environment are proposed to impact obesity including urban sprawl, land-use mix, food environment, crime rate, walkability, and green space. The primary channel through which urban green space is proposed to impact obesity is through increased physical activity. However, as identified by Lachowycz and Jones (2011) who performed a systematic review of the pre-existing literature, there is a large amount of conflicting evidence regarding the association between obesity and urban green space. In particular self-selection effects can be difficult to control for due to data limitations (Boone-Heinonen, Gordon-Larsen, Guilkey, Jacobs, and Popkin, 2011).