Limited access to supermarkets not the only cause of obesity in food deserts, research finds

Rather, encouraging consumers to select more healthy food options by providing nutrition education and removing transportation barriers to existing outlets for healthy food “could play a more beneficial role,”​ argues Di Zeng of the University of Arkansas in research he presented Jan. 4 at the Allied School Sciences Association Annual Meeting in San Francisco.

He explains in the paper​ that “food deserts are increasingly hypothesized as a causal factor of overweight and obesity in the US”​ because they tend to have fewer supermarkets, which offer more healthy options at a lower price than convenience stores, which are more prevalent in food deserts and sell more energy-dense, processed foods.

Although this theory is “reasonable”​ given that fresh fruits and vegetables are less available and more expensive in convenience stores than grocery stores, Zeng argues that “the dichotomy of supermarkets with healthy foods and convenience stores without … could be an oversimplification and the results may not apply to all individuals.”​

Using a rational-choice framework, the study found the causes of obesity epidemics in food deserts, which Zeng does not deny, are “far more complicated”​ than access to supermarkets measured by distance and income levels.

In fact, the framework suggests that contrary to popular belief, “longer distance to the supermarket does not generally increase weight, yet in certain cases a shorter distance does.”​

Zeng explains consumers who walk to the grocery store benefit from the added exercise to cover longer distances, which will either offset the consumption of unhealthy food – which is equally available at c-stores and supermarkets – or magnify the benefits of a healthy diet.

When the distance is reduced, so too is the exercise, Zeng argues. In addition, the easier access to less expensive junk food at supermarkets, compared to the higher priced alternatives at c-stores, could increase consumption of unhealthy foods by people who prefer them, the study shows.

That said, the research model also recognizes the impact of time and financial costs of traveling long or short distances also will influence weight.

For example, a consumer who would rather eat healthy food, but has limited time to travel long distances often, may restrict the number of trips. In doing so, the healthy consumer also might restrict the purchase of fresh, but perishable, food for fear it would spoil before the next trip. In this scenario, the consumer might mix in more processed, shelf stable food that is more energy dense, which could lead to weight gain.

If a consumers is highly dedicated to healthy eating, however, she likely will opt to eat less or decide the time investment to get to the store is worth it for more trips, Zeng says.

Thus, an individual’s preferences become a confounding factor beyond just distances to a supermarket.

Income is a confounding factor​

A consumer’s income also becomes an ambiguous confounding factor for food purchase decisions that could swing towards healthy and unhealthy selections alike, Zeng notes.

“The ambiguity of the income-weight relationship may at first appear counterintuitive, given the fact that higher obesity rates are indeed observed in food deserts,”​ Zeng writes. But, “there is consistent evidence that the effect of income on weight is generally unclear and could be the net effect of numerous mechanisms.”​

For example, Zeng writes: “for healthy eaters, income reduction unambiguously decreases weight”​ because they cannot afford to buy as much healthy food, which generally is more expensive than junk food, and therefore they consume less.

For someone less health-conscious than cost-conscious however, lower income could lead to the purchase of more energy dense and less expensive junk food, Zeng notes.

Even if this person had access to less expensive healthy food, he or she may still prefer the taste of junk food and continue to buy it, Zeng said.

Given the confounding factors of individual preferences and travel cost on food purchases and weight gain, Zeng concludes “nutrition education could be a potentially effective tool” ​in enhancing healthful food preferences by food desert residents and ultimately influencing their purchases, even from unhealthy food retailers if supermarkets continue to be scarce.