The local food environment and diet: A systematic review

Abstract

Despite growing attention to the problem of obesogenic environments, there has not been a comprehensive review evaluating the food environment–diet relationship. This study aims to evaluate this relationship in the current literature, focusing specifically on the method of exposure assessment (GIS, survey, or store audit). This study also explores 5 dimensions of “food access” (availability, accessibility, affordability, accommodation, acceptability) using a conceptual definition proposed by Penchansky and Thomas (1981). Articles were retrieved through a systematic keyword search in Web of Science and supplemented by the reference lists of included studies. Thirty-eight studies were reviewed and categorized by the exposure assessment method and the conceptual dimensions of access it captured. GIS-based measures were the most common measures, but were less consistently associated with diet than other measures. Few studies examined dimensions of affordability, accommodation, and acceptability. Because GIS-based measures on their own may not capture important non-geographic dimensions of access, a set of recommendations for future researchers is outlined.

Introduction

The body of literature on the local food environment and its effects on health has been growing, particularly in response to evidence of “food deserts” pocketing the US urban landscape (Michimi and Wimberly, 2010, Zenk et al., 2005). Yet, to date, there has not been a comprehensive review of the relationship between the local food environment and dietary outcomes. Previous food environment review articles have generally fallen into two categories. First, review articles have focused their discussion on disparities in access to healthy foods, including the existence of food deserts and neighborhood characteristics associated with food deserts (Larson et al., 2009, Walker et al., 2010). Other articles exploring the effects of food deserts have touched upon diet while focusing primarily on obesity as an outcome (Black and Macinko, 2008, Casagrande et al., 2009, Ford and Dzewaltowski, 2008, Holsten, 2009, Lovasi et al., 2009). For the most part, these reviews present comprehensive and theoretically sound discussions of the environmental determinants of obesity. Yet there has been relatively little discussion specifically devoted to what is conceivably the primary mechanism through which “obesogenic” settings operate – namely, the food environment–diet relationship.

Studies exploring the food environment–diet relationship have used a wide variety of methodologies to measure the degree of food access for study participants. In the past two decades, the increased use of Geographic Information Systems (GIS) technology has resulted in an outpouring of exposure assessment techniques (McKinnon et al., 2009). These measures commonly use store density (using buffer distances), or proximity to the nearest food store to operationalize food access (Charreire et al., 2010), although finding appropriate and consistent criteria for defining geographic boundaries has proved challenging (Charreire et al., 2010). Another common objective method for assessing food access is store audits, in which researchers visit stores and estimate the shelf-space occupied by certain foods in each store, or assess product variety or food prices within stores. Validated store audit measures, such as the Nutrition Environment Measure Survey (NEMS), have often been used to evaluate such store features (Glanz et al., 2007), although such measures have been used infrequently in studies linking food environments to health outcomes.

Still others studies have relied on respondent-based perceived measures to capture the food environment, including perceived availability and accessibility of food or food stores. Though uncommon, a few studies have used both a perceived and an objective measure in their study – for example, the availability of healthy food in the neighborhood and store density. In general, the proportion of studies using perceived measures of the food environment is small compared with those that use GIS-based methods; by 2007, GIS-based measures of the food environment outnumbered interview/questionnaire measures 57 to 10 (McKinnon et al., 2009), and the use of GIS measures is only likely to increase if current trends continue (Charreire et al., 2010). Undoubtedly, because of extensive variation in the operationalization of the local food environment, many measurement challenges remain unaddressed (Lytle, 2009) (Fig. 1).

Despite major measurement inconsistencies, previous review articles have yet to examine comprehensively how the food environment–diet study results have differed according to the method of exposure assessment. One previous review article sorted results by exposure assessment type, but examined only the fast food environment (Fraser et al., 2010). A recent set of two reviews sought to overview different indicators of the food environment, but one included only GIS-based measures (Charreire et al., 2010); the other examined only non-geographic measures and stopped short of linking the different exposure measures to actual dietary outcomes (Kelly et al., 2011).

A theoretical framework for conceptualizing the local food environment: Beyond the strictly methodological task of selecting the best exposure assessment technique lays a more theoretical question concerning the very definition of food access. Frequently, food environment conceptualizations have been divided into the community food environment and the consumer food environment (Glanz et al., 2005), drawing a useful distinction between the distribution of food sources within a community and what consumers encounter while inside their local retailers. Several previous articles have also begun to explore even more subtle conceptualizations of the food environment (Charreire et al., 2010, McKinnon et al., 2009), including the different dimensions of access that food environment measures have actually tapped into. Although a complete list of such dimensions has never been compiled, it has been suggested (Charreire et al., 2010) that one way of conceptualizing food access dimensions is by adapting a model of access proposed by Penchansky and Thomas, who outlined 5 dimensions relevant in the healthcare setting (Penchansky and Thomas, 1981). These dimensions include availability, accessibility, affordability, acceptability, and accommodation.

The first three are the most obviously familiar in the existing body of literature. Availability refers to the adequacy of the supply of healthy food; examples in the food environment might include the presence of certain types of restaurants near people's homes, or the number of places to buy produce. The dimension of accessibility may be more inherently geographic, as it refers to the location of the food supply and ease of getting to that location. Travel time and distance are key measures of accessibility. Affordability refers to food prices and people's perceptions of worth relative to the cost, and is often measured by store audits of specific foods, or regional price indices. Acceptability refers to people's attitudes about attributes of their local food environment, and whether or not the given supply of products meets their personal standards. As an attitudinal variable, it may be ideally measured by surveying participants; however, there have been a few creative attempts to estimate food acceptability by more objective means – for instance, by having store auditors assign food quality scores to produce. Accommodation, or how well local food sources accept and adapt to local residents' needs, is the final dimension of access. It is largely open to exploration in the current literature but could, for example, refer to store hours and types of payment accepted.

The primary aim of this paper is to evaluate the existing body of literature on the relationship between the local food environment and diet, with particular attention placed on the method of characterizing of the food environment. The secondary aim of this study is to explore the variety of conceptual definitions of “food access” within this body of literature. The relationship between food environments and diet will be diced according to different quantitative assessments of the food environment, as well as the different dimensions of access that could underlie each measure. Finally, this paper will identify understudied dimensions of “food access”, and make recommendations for future directions for the optimal study and improvement of food environments.