Abstract
BackgroundObesity remains one of the most challenging public health issues of our modern time. Despite the face validity of claims for influence, studies on the causes of obesity have reported the influence of the food environment to be inconsistent. This inconsistency has been attributed to the variability of measures used by researchers to represent the food environments—Researcher-Defined Food Environments (RDFE) like circular, street-network buffers, and others. This study (i.) determined an individual’s Activity Space (AS) (ii.) explored the accuracy of the RDFE in representing the AS, (iii.) investigated the accuracy of the RDFE in representing actual exposure, and (iv.) explored whether exposure to food outlet reflects the use of food outlets.MethodsData were collected between June and December 2018. A total of 65 participants collected Global Positioning System (GPS) data, kept receipt of all their food purchases, completed a questionnaire about their personal information and had their weight and height measured. A buffer was created around the GPS points and merged to form an AS (GPS-based AS).ResultsStatistical and geospatial analyses found that the AS size of participants working away from home was positively related to the Euclidean distance from home to workplace; the orientation (shape) of AS was also influenced by the direction of workplace from home and individual characteristics were not predictive of the size of AS. Consistent with some previous studies, all types and sizes of RDFE variably misrepresented individual exposure in the food environments. Importantly, the accuracy of the RDFE was significantly improved by including both the home and workplace domains. The study also found no correlation between exposure and use of food outlets.ConclusionsHome and workplace are key activity nodes in modelling AS or food environments and the relationship between exposure and use is more complex than is currently suggested in both empirical and policy literature.
Highlights
Obesity remains one of the most challenging public health issues of our modern time
Full list of author information is available at the end of the article
Three participants withdrew before data collection and eight participants were excluded due to errors in their Global Positioning System (GPS) data resulting in a final sample of 65
Summary
This study was undertaken between June and December 2018. It included participants residing in Leeds, UK and its surrounding areas, aged 18 years old and above, with proficient digital skills (e.g. smartphone, laptop or computer) and access to the internet. The collected GPS data were used to create a buffer of 1 km on both sides of the road network which was considered as an AS (GPS-based AS) This buffer size was considered a reasonable estimate of how far a person would walk [28, 65] and captures the adjacent area to individual daily paths. 2 SDE were created to capture 95% of all GPS points of participants movements. The orientations of 2 SDE were assessed for agreement with home-workplace direction and recorded as a binary variable (yes/no) (see Fig. 1). The PoI data set was used to identify and map all food outlets in the study area. The PPV in this study denoted the proportion of food outlets within the RDFE that were truly present in an individual’s AS. Exposure referred to food outlets within a defined environment and use referred to the food outlets in which the participants purchased food
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