The Complicated Connection Between Supermarkets and Obesity

Like most food system “solutions,” supermarkets and food retail in general are a lot more complicated than we want them to be. Reading headlines would lead one to believe that once healthy food is readily available, it is reasonable to expect a reduction in obesity (or improvement in other diet-related issues). There has been a steady drumbeat of researchers challenging that notion, but their message rarely makes it beyond the academic literature (Tamar Haspel’s piece and Vaugh & Dubowitz’s article are recent exceptions). To understand how food access became such a prominent focus, it is worth reading an article published in the Fordham Urban Law Journal by Rosenberg and Cohen, which documents the evolution of food access, the conclusive and inconclusive evidence and recommendations to address some of these systemic problems.  

Most advocates seeking solutions to diet disparities would not claim that food retail alone will solve the problem. In our search for solutions, though, food retail has absorbed a large share of the attention. Certainly, retail needs to play a significant role; people do most of their shopping at supermarkets, with superstores a very close second. But we need to temper our expectations that supermarkets alone can drive change. Like any business, supermarkets need to make money. In order for supermarkets to stay in business, they have to sell what people want to buy, which includes healthy and less healthy foods. To understand some of the complexity of why supermarkets would only make a dent in the problem, it’s important to understand where conventional wisdom conflicts with research findings.  

• Conventional Wisdom: If you put a grocery store in a neighborhood without one, people will change their shopping locations. 
  • What the Research Says: On average, people shop at five different food outlets, regardless of income, and they don’t shop at the store closest to them.  The mean trip distance is 4.8 miles for people with household incomes of $25,000 or less.  So even if you have a store close to you, that doesn’t mean you’ll shop there. People of all income levels pick shopping locations based on price, quality, and convenience.
• Conventional Wisdom: Low-income households shop for food at their local corner stores or bodega.  
  • What the Research Says: Regardless of income, most people do their food shopping at supermarkets or superstores.  One report noted that while lower income households make fewer shopping trips, they spend the same percentage of their weekly food expenditures at supermarkets or superstores as non-low-income households.  Low-income households do spend more per capita at convenience stores, drug stores and dollar stores, although non-low-income households are just as likely to shop at these stores for food.  Due to low volume and more limited supply chains, prices in smaller stores tend to be higher than supermarkets, which exacerbates the cost burden for households who rely on them to fill the gap between shopping trips.  
• Conventional Wisdom: Increasing access to supermarkets leads to healthier purchasing.  
  • What the Research Says: Because supermarkets offer many less healthy foods along with healthy foods, increasing access alone does not change purchasing patterns. For most people, behavior changes take time. There is evidence that changing the store’s environment (e.g. shelf labels, product placements) can change purchasing patterns, and evidence that increased access changes residents’ perceptions of their food environment.  Both of these factors are important because they can reinforce changes in shopping behavior.
• Conventional Wisdom: Prices for healthy food items are higher in supermarkets located in low-income areas, which is why people don’t purchase them.  
  • What the Research Says: With the exception of some fresh produce, and that is a notable exception, prices for healthier food items are actually lower in supermarkets in low-income areas.  That does not mean, however, that the food is affordable to low-income households. One study found that households with poor food access (defined as more than .5 mile from a supermarket and not owning a vehicle) have a significantly lower median monthly income ($1,240 compared to $4,388) than those households with adequate food access.  Further complicating the situation, one study found that 40% of low-income people live in non-low-income areas, which means food in their area is even less affordable.  

No single solution will solve the problem of diet disparities; real change will require systems change. Such change happens when people come together to identify the multiple issues causing diet disparities, understand how those issues are related to and interact with each other, and begin to attend to their root causes.  

This blog post inspired a follow-up from researchers at the University of Delaware. Read "The 10 Things Food Advocates Need to Know Before Working with a Supermarket."