Creating ‘obesogenic realities’; do our methodological choices make a difference when measuring the food environment?

Abstract

BackgroundThe use of Geographical Information Systems (GIS) to objectively measure ‘obesogenic’ food environment (foodscape) exposure has become common-place. This increase in usage has coincided with the development of a methodologically heterogeneous evidence-base, with subsequent perceived difficulties for inter-study comparability. However, when used together in previous work, different types of food environment metric have often demonstrated some degree of covariance. Differences and similarities between density and proximity metrics, and within methodologically different conceptions of density and proximity metrics need to be better understood.MethodsFrequently used measures of food access were calculated for North East England, UK. Using food outlet data from local councils, densities of food outlets per 1000 population and per km2 were calculated for small administrative areas. Densities (counts) were also calculated based on population-weighted centroids of administrative areas buffered at 400/800/1000m street network and Euclidean distances. Proximity (street network and Euclidean distances) from these centroids to the nearest food outlet were also calculated. Metrics were compared using Spearman’s rank correlations.ResultsMeasures of foodscape density and proximity were highly correlated. Densities per km2 and per 1000 population were highly correlated (rs = 0.831). Euclidean and street network based measures of proximity (rs = 0.865) and density (rs = 0.667-0.764, depending on neighbourhood size) were also highly correlated. Density metrics based on administrative areas and buffered centroids of administrative areas were less strongly correlated (rs = 0.299-0.658).ConclusionsDensity and proximity metrics were largely comparable, with some exceptions. Whilst results suggested a substantial degree of comparability across existing studies, future comparability could be ensured by moving towards a more standardised set of environmental metrics, where appropriate, lessening the potential pitfalls of methodological variation between studies. The researchers’ role in creating their own obesogenic ‘reality’ should be better understood and acknowledged.

Concerning Limitations of Food-Environment Research: A Narrative Review and Commentary Framed around Obesity and Diet-Related Diseases in Youth

“…100 One strategy commonly used to define "exposure" in food-environment studies is to use administrative areas such as block groups, census tracts, or zip codes (Figure, panel A). ‡ Such administrative areas may be quite problematic for food-environment conclusions though, because there could be highly uneven exposures within administrative boundaries.…”

How can GPS technology help us better understand exposure to the food environment? A systematic review

“…One area of particular interest has been the influence of the macro-level food environment on weight and associated dietary behaviours, food intake, and food purchasing (Bader et al, 2010, Burgoine et al, 2013). …”

“…These include GIS (geographical information systems) (Moore, Diez Roux, Nettleton, Jacobs, & Franco, 2009), global positioning systems (GPS) (Zenk et al, 2011), smartphones (Boulos and Yang, 2013, Iverson,), tablets (Boulos & Yang, 2013), PDAs (handheld personal digital assistants) (Fitzgerald, 2005), Google Maps (Wang et al, 2011) and smart card technology (Lambert et al, 2005). Much of the evidence in the literature is however based on the use of GIS to compute measures of assumed exposures to the food environment based on the location of facilities (Burgoine et al, 2013) and typically focused on residential neighbourhoods with indicators of proximity/density used to describe retail food accessibility (Christian, 2012). Despite their popularity, these methods have several limitations.…”

Obesogenic environments: current evidence of the built and food environments

“…A systematic review of obesogenic environment papers included seven studies, associating physical activity and greenspace, but none of the papers used the same definition of this metric 4 . The review provides a good example of the problem of the multiple approaches, metrics, and definitions employed in obesogenic environment research since its inception 24 .…”