Food access and obesity

Human diet and nutrition has long been known to influence health outcomes. The major focus of research during the last hundred years has been on the relationship between nutrient intakes and disease processes at a physiological level. In the post-war years, separate strands of research emerged primarily in the UK and the USA: on food retailing, from economic and planning perspectives; and on dietary patterns and dietary behaviour change, focusing on prevention of chronic non-communicable diseases such as coronary heart disease. Only with the emergence of interest in and, more recently, a UK policy focus on health inequalities, has the link been made explicitly between food retail access and dietary intake. From the early 1990s onwards, this research increasingly sought to answer the questions of whether urban ‘food deserts’ exist, and if so how they are caused and whether they can be tackled by modifying the food retail environment. In the last 5 years, this integrated strand of research has broadened and converged with a parallel strand of research on understanding the ‘obesogenic environment’. This new field of research has predominantly explored the effects of the built environment on physical activity, but has now also started to explore the availability and accessibility of retailed foods. A recent addition to this strand is research on the spatial patterning of and food availability in restaurants and fast-food chains. Little research on food access has explicitly looked at obesity as an outcome. However, the relationship between obesity and the ‘healthiness’ of diet, in terms of measures such as fruit and vegetable consumption or fat intake, is strong. Evidence demonstrating effects of retailing on diet and food purchasing has therefore been deemed relevant to this review. The nutritional quality of dietary intake is strongly patterned socioeconomically (1–13). A range of nutritional deficits, judged by current national recommendations in the UK, are more commonly found among those in lower socioeconomic groups, as well as among the elderly, teenagers, young adults and men. Many factors are known to contribute to dietary behaviour at a household or ‘family’ level, including disposable income; gender; the knowledge and skills of those purchasing, preparing, storing and serving food; influences such as advertising; and practical constraints within the household such as the availability and adequacy of facilities for preparation, cooking, cold and dry storage, and the consumption of food (1,2,14–24). Such research on the social patterning of diet has been replicated in other countries, in particular, the USA (17,24–29). The most recent development in this field has been the emergence of studies focusing on wider ‘environmental’ determinants of diet outside the home. In the early 1990s, the socioeconomic patterning of health variables, including health-related behaviours, were shown to have significant spatial patterning (30). In studies from Scotland (30–33) and elsewhere (2,25,26,34), the influence of area of residence has been shown to be a potent predictor of dietary patterns, over and above individual or household socioeconomic factors. Most recently, the focus of research interest has shifted to the potential environmental causes of observed inequalities in diet, in particular, food retailing. Much research has documented the changing landscape of food retailing in the post-war era, both in the USA and the UK. There are no comprehensive reviews, although the work of several British authors provides useful summaries (35–40). In summarizing what is available, a complex set of relationships and developments will inevitably be oversimplified. Research from the UK, as well as parallel work from the USA, documents a major retail revolution in food supply since the 1960s (41–51). The causes of these developments can be attributed to both supply and demand factors: changes in food retailing have been driven by the industrialization of agriculture and commercial forces, but these in turn have been influenced by socioeconomic and cultural shifts, such as the growing number of women in employment and increasing car ownership (52). Together, these factors have led to a greater demand for one-stop shopping and a greater willingness to travel to shops viewed as offering better value for money, quality and range of goods – a demand that was readily met by the major retailers (39). The most visible change has been the rapid growth of large multiple/chain-owned supermarkets in out-of-town locations, usually on main arterial or circular roads near to major urban conurbations. This has resulted in a decline in the numbers of smaller general and specialist grocery shops in town centres and suburban areas, which were unable to compete with the higher turnover and lower prices of supermarkets. The emerging pattern of modern retailing in the UK has therefore been dominated by a small number of major retailers (e.g. Tesco, Asda, Sainsbury, Morrison, etc.) with a predominance of large, out-of-town supermarkets carrying a huge range of lines at low prices, and smaller local stores increasingly diversifying to become all-encompassing ‘convenience’ stores maintaining higher prices driven by their turnover in order to compete (35). It was in this climate that concerns first emerged about the lack of food retail provision in some urban areas, and the term ‘food deserts’ was coined, linking the retail revolution inextricably with the socioeconomic patterning of diet highlighted above. The term is usually used to describe urban areas where it is difficult to buy a range of food necessary to eat healthily at a reasonable price (35,53–58). It is reported to have been used first by a resident of a public sector housing scheme in the west of Scotland in the early 1990s (59). It was picked up and used by the Policy Working Group of the Government’s Low-Income Project Team of the Nutrition Task Force in 1995 (5). The concept was then investigated by the Social Exclusion Unit’s Policy Action Team 13, in its review of shopping access for people living in deprived neighbourhoods (60). The idea of food deserts had immediate appeal to the media and policymakers, and rapidly became enshrined in government policy (39,54): it was mentioned in the National Health Strategy (61) and the Government’s independent enquiry into health inequalities (62). However, it is important to recognize that it has little scientific basis (55). By the mid-1990s, the economic climate had begun to change again. Two factors influenced further developments in the UK: the introduction of planning guidance aimed at revitalizing urban centres; and the rapid emergence of a new European-style ‘deep discounter’ (e.g. stores such as Aldi, Netto, Lidl), selling a limited number of lines at prices that undercut the major supermarkets (63). Together these factors led to a further change of track by the major retailers, with the introduction of new, smaller formats in a diverse range of settings (e.g. Tesco Metro and Tesco Express stores in city centres and petrol stations). Although this recent trend might have been expected to fill gaps in retail provision in urban areas, the major retailer’s smaller-format stores are invariably more expensive than their larger ones, a practice known as ‘price-flexing’ (63). This was one of the problematic issues identified by the Competition Commission in its review of supermarkets in 2000, but led to no more than a recommendation for self-regulation by the big players (64). Ultimately, the major retailers’ smaller stores retain a competitive edge over independent convenience stores by virtue of the economies of scale that underpin them (e.g. massive distribution networks, own brand products, etc.) (63). One other area of development is worthy of note. As well as developing formats and pricing strategies to meet commercial demand over the last 30 years, the major retailers have responded to consumer demand by massively expanding the range and quality of foods available (65). A key development attributable to this sector (and to Marks and Spencer in particular) has been the ‘ready meal’. This concept has been developed by all the major supermarkets to include a diverse range of convenience foods. Such foods have been criticized for their ‘healthiness’, especially their high-fat, sugar and salt content, but have become hugely popular and profitable (63,66). Another development was the introduction of ‘economy’ lines (such as Tesco ‘Value’ products) by all the major supermarkets in direct response to the commercial threat posed by the discount supermarkets (63,67). Some supermarkets (notably Sainsbury and Tesco) have also introduced ‘quality’ ranges (e.g. Sainsbury ‘Taste the Difference’) in order to compete with the major high-end retailers, such as Marks and Spencer. These developments, as well as huge diversification in non-food sales and a large number of mergers and acquisitions, have enabled the key competitors to retain market domination and maintain generally low food prices (63). This is a critical issue because, although the big players have been blamed for the demise of local, independent grocers, they have also been responsible for delivering considerable value to consumers. With the emergence of concerns about ‘food deserts’, a new strand of research evolved in the UK (and more recently in the USA), aimed at assessing food retail access for individuals and households. While the focus of research on retailing had been on the number, type and size of stores, this new work focused, in addition, on assessing the range, cost and quality of foods available in stores in geographically defined neighbourhoods. Early work defined methods, using a range of ‘healthy food basket’ methods (68–75) and definitive studies then started to demonstrate a mix of findings. Although some early studies suggested that ‘healthy’ foods may be more expensive and less available in poorer areas (74), more recent studies have failed to replicate these findings, showing instead that ‘healthy’ foods tend to be as, if not more, available in poorer areas and are lower in price (39,63,72,73,76–78). However, these studies have demonstrated consistent differences between types of store – larger grocery shops, not surprisingly, generally have greater availability, lower costs and better-quality fresh produce than smaller grocery stores. Nevertheless, some small specialist stores (such as greengrocers and market stalls) appear to offer even cheaper prices for fruits and vegetables than supermarkets (78). Another strand of work has explored modes of transport used and physical proximity to food stores by socioeconomic variables, as well as the attitudes and preferences of low-income consumers. This research consistently demonstrates that car ownership and use of a car to buy food is socioeconomically patterned and that this is a key determinant in choice of main food stores (15,49,50,52,56,68,73,78–85). It also shows that carrying shopping, as well as the problems of storage, remain important barriers to accessing supermarkets by the poor (50,52,56,73,78–80,84,85). Nevertheless, the poor demonstrate sophisticated strategies for ‘economic’ shopping, utilizing a wide range of store types including markets, discount stores, supermarkets and convenience stores to buy the food they need to feed their families from one payday to the next (86,87). Although a huge majority use a car or public transport to travel to shops in the UK, those who walk or cycle to shops travel relatively small distances (78), suggesting that mode of transport may only contribute a small amount to daily energy expenditure. One of the key concerns in the ‘food deserts’ debate has been the question of whether a ‘healthy’ diet costs more than an ‘unhealthy’ diet. There has been a modest amount of research on the cost of a nutritionally adequate diet, including studies to define a ‘modest but adequate’ diet (69), but no reviews. In a study in the Hampstead area of London, Mooney showed that two diets, one meeting and one not meeting contemporary nutritional guidelines, differed in cost, with the ‘healthier’ diet consistently costing more (68). However, she also showed that both more and less healthy diets were consistently cheaper in more deprived than in more affluent neighbourhoods, but failed to draw attention to this in her conclusions. Perhaps for this reason, her study has been widely misquoted as demonstrating that healthy food costs more in more deprived areas. More recent research using more ‘realistic’ family food baskets has confirmed these findings and showed that availability of a ‘healthy’ diet increased from 1990 to 1994 and the cost declined in supermarkets. Availability and cost in local grocers remained poor (83). One interesting analysis of cost relates to ‘economy’ line products (mentioned above). Cooper and Nelson analysed a range of such products for nutritional content and found them to be as healthy as, if not healthier than, equivalent standard products and excellent value for money (67). While many regard such products as inferior on grounds of taste, they clearly can play a role in eating healthily on a low income. One of the few studies to come from outside the UK or the USA presented an economic analysis aimed at predicting the food choices individuals might make in order to reduce their food budget (by simulating the choices made by low-income French consumers) (88). Increasing cost constraints decreased the proportion of energy contributed to diet by fruits, vegetables, meats and dairy products, replacing these with cereals, sweets and added fats, thus reducing overall nutrient density – a pattern similar to that observed in the diets of lower socioeconomic groups. The authors concluded that economic measures would be needed to effectively promote healthier diets among the poor as, no matter how good the level of access, the poorest, ultimately, cannot afford the healthiest diet. So far, reference has only been made to separate bodies of work that have looked at retail access and the social patterning of dietary intake. Only a small number of studies have attempted to assess whether food retailing directly influences diet. This body of work can be divided into three groups: ecological studies that compare food retail access and diets within geographical areas, but do not look at where individuals buy their food; studies that explore cross-sectionally the relationship between food retailing and dietary intake in individuals; and experimental studies that explore whether changes in retail provision result in changes in the diets of individuals who live near to and/or shop in specific retail outlets. This group of studies has typically looked at the correlation between a measure of food access in geographical areas and a separate measure of diet in the same areas and drawn conclusions about causality. For example, Morland et al., analysing data from the Atherosclerosis Risk in Communities (ARIC) study, demonstrated that both and fruit and vegetable intake was higher in with more and concluded that the local food environment is important for diet However, they not have data on where people their food and only data on a limited range of grocery stores. they that their food at supermarkets in their own – a that from other retail research is A small number of studies have socioeconomic factors and food purchasing or of store etc.) in individuals These on the socioeconomic (and in some patterning of food purchasing, do not answer the question of whether food retail access to A study from the only study that has data on the diets of individuals and retail availability and access (78). a range of the authors were unable to demonstrate that retail including availability, proximity or were with dietary The factors that of diet, in terms of fruit and vegetable or fat intake, were dietary other of a healthy such as more or less and socioeconomic factors. demonstrated that retail access is generally good in all of the with some in poorer areas (e.g. more and cheaper fruit and However, they confirmed the findings of that availability, price and quality are in with convenience stores. While some of the that retail availability has only a on dietary patterns, this study was limited by its Two studies have of the development of a new, large both a Tesco in areas of the UK. The study from a no area and a size small to small changes in behaviour The authors reported a on fruit and vegetable among those who to the new A study from in showed little on fruit and vegetable consumption among local or changes were similar in to those in the that the effects in a were by a change The study with the study (78), provides the most and to that food retail access not have a on dietary in the UK at The research presented so not that food retailing in diet and it is therefore reasonable to that it is also to have a on is not to that other such as are not but in the overall scheme of about retail availability and access may not be the most profitable for about modifying diets in the One recent review has of the to similar conclusions The authors suggested that a between the findings of studies from the USA and other developed important differences between the USA and The is that the USA is a more where issues such as food retail access are for the poor and, in particular, Evidence from a range of studies of health as well as studies of the retail to such a There is also one recent study that has explicitly looked at the relationship between food retailing and This is study from Morland et al., analysis the data and from the same as its among and was with lower numbers of supermarkets and higher numbers of convenience stores in However, was no that individuals within their own and these may be by the socioeconomic of neighbourhoods, that people live in poorer areas, by supermarkets and more convenience stores. In study from have recently the data to explore the between retail factors and obesity by body from and have found no of an of food retailing, although further work is One relatively new, area of research a studies have begun to explore the role of food (and outside the in predicting While food outside the can be nutritionally inferior to food and can contribute to energy an with has not been demonstrated However, two areas have been in the USA, provision of healthy as well as and in the UK and of fast-food outlets. From the USA, et have a relationship between of consumption of food from fast-food restaurants in and development of obesity Two studies have shown to be more fast-food restaurants in predominantly areas and one has demonstrated healthier available in restaurants in such areas In the UK, et failed to socioeconomic patterning by small area of food in but that fast-food restaurants were more to be found in more deprived areas in and Scotland In et found the density of fast-food to be greater in more deprived areas. The huge of research on this issue has only begun to answer the question of whether retail access dietary intake. A key to be that studies and are to do and of or major studies are It is also difficult to within the that from the retail sector is also needed to such studies from energy but it is to what this from energy consumption or from energy that these are and can be about the to which diet is in the of to food access may become The edge in this field are studies where both retail factors (e.g. access, availability and and diet are as to so that the of can be and with an experimental so that change in diet can be on change in retail Only one such experimental study has been to and further studies are in a range of conclusions can be More research is also needed to the role and of food and outside the in fast-food and other the relationships that have emerged from the research to not a of all of this For example, is a significant body of and research that the by the poor in a healthy diet and is further research on access to facilities for the storage, and serving of food in (78). There is also further research focusing on of using methods and price that may be relevant to the prevention of obesity A more and review of all the relevant research so as to the further development of such an would be of to understanding of will remain but in parallel with research to and where are for relationship between socioeconomic factors and dietary intake, by food retailing. are highlighted in in Some of these have been the of research (e.g. to dietary knowledge and dietary but a range of other areas skills and preferences remain important cultural determinants of the of diet and not be A review of the on food and food budget was the of the review. However, the research demonstrating the socioeconomic patterning of diet and the the effects of cost constraints on dietary choices of research the potential for economic such as to low-income may potential research on increasing access to and other also be of The for of food retailers in developing price may be more but is also have developed focusing on the of food retail access (52). Such an a from that presented but to draw attention to other potential for for obesity such as on food and policy (e.g. of and of food retailers, and other food of interest was