Supermarkets, Other Food Stores, and Obesity

Background

Obesity is a leading public health concern, and although environmental factors have been hypothesized to play a role in the prevention of obesity, little empirical data exist to document their effects. The purpose of this study was to examine whether characteristics of the local food environment are associated with the prevalence of cardiovascular disease risk factors.

Methods

A cross-sectional study of men and women participating in the third visit (1993–1995) of the Atherosclerosis Risk in Communities (ARIC) Study was conducted in 2004. The analyses included 10,763 ARIC participants residing in one of the 207 eligible census tracts located in the four ARIC-defined geographic areas. Names and addresses of food stores located in Mississippi, North Carolina, Maryland, and Minnesota were obtained from departments of agriculture. Multilevel modeling was used to calculate prevalence ratios of the associations between the presence of specific types of food stores and cardiovascular disease risk factors.

Results

The presence of supermarkets was associated with a lower prevalence of obesity and overweight (obesity prevalence ratio [PR]=0.83, 95% confidence interval [CI]=0.75–0.92; overweight PR=0.94, 95% CI=0.90–0.98), and the presence of convenience stores was associated with a higher prevalence of obesity and overweight (obesity PR=1.16, 95% CI=1.05–1.27; overweight PR=1.06, 95% CI=1.02–1.10). Associations for diabetes, high serum cholesterol, and hypertension were not consistently observed.

Conclusions

Results from this study suggest that characteristics of local food environments may play a role in the prevention of overweight and obesity.

Introduction

The U.S. Public Health Service has identified obesity as a leading health concern.¹ The prevalence of obesity has been increasing in the United States, and disparities in both conditions exist by gender, race/ethnicity, and socioeconomic status.2, 3 For example, the prevalence of overweight and obesity is greater among nonwhite women compared to white, non-Hispanic women. In addition, a 50% higher prevalence of obesity has been reported in poor compared to nonpoor women.1, 4

The increasing rates of obesity have both health and economic consequences, because individuals who are obese are at greater risk of developing comorbidities.⁵ In particular, diabetes has been steadily increasing; black Americans, Hispanic Americans, and those with lower education and income are more likely to develop the disease.6, 7, 8 The economic consequences of obesity has been estimated at 280,000 to 300,000 deaths per year,⁹ and the U.S. cost for treatment and lost wages is estimated to be over $110 billion.¹⁰

The high prevalence of obesity results from the interaction of environmental, behavioral, and genetic factors. Although genetic factors are important for determining individual susceptibility to becoming overweight, broadly defined environmental factors such as changes in agriculture, food processing and marketing, transportation, physical demands of work, and the contextual effect of residential areas create the context for the population distribution of adiposity. These environmental factors affect obesity through their effects on physical activity and diet.

At the same time that the prevalence of overweight and obesity has been increasing in the United States, levels of physical activity have been decreasing, such that the Task Force on Community Preventive Services has made the recommendation for physical activity to combat these increasing rates.11, 12 Environmental characteristics that have recently received attention as determinants of physical activity include aspects of urban sprawl,¹³ accessibility of recreational resources,14, 15 and neighborhood safety.16, 17

Although the consumption of total fat and saturated fat has decreased over the past 30 years, the intake of calories and carbohydrates has increased.¹⁸ The consumption of specific food items such as soft drinks and sugars has also risen.19, 20, 21, 22, 23 These trends toward energy-dense diets are thought to be a result of a variety of factors including increasing portion sizes24, 25 and changes in food production, marketing, and pricing.26, 27, 28, 29 Energy-rich foods (i.e., sugars, breads, pastas) are less expensive, which may make these foods especially attractive to people with limited incomes. The increasing availability of pre-packaged foods has also been suggested as a factor contributing to the intake of energy-rich foods.30, 31

In addition, food availability at the neighborhood level has recently received attention as a possible environmental determinant of diet.32, 33 Some investigators have documented disparities in the costs of foods34, 35, 36 among areas, while others have shown differences in the availability of certain types of food stores.34, 35, 36, 37, 38, 39, 40, 41 Other researchers have focused on the types of foods available within food stores; for instance, Sallis et al.⁴² found that U.S. supermarkets offer a large variety of healthy foods. Other investigators support these findings in which associations between healthy diets and supermarket availability have been documented.43, 44 More recent studies have begun to show an association between the availability of places to obtain foods and obesity.45, 46 Little data exist on the contents of other types of food stores, such as convenience stores, that are assumed to carry a larger proportion of energy-dense foods. Since the food choices that people make are limited to what is available to them, and convenience is an important predictor for food habits,47, 48 it is hypothesized that individuals living in areas with few food choices other than convenience stores may be more likely to adopt an energy-dense diet. Conversely, food environments offering a greater variety of healthy food options at affordable prices may lead to healthier food choices.

The objective of this study was to determine if there is an association between the availability of supermarkets, grocery stores, and convenience stores and cardiovascular disease (CVD) risk factors. Because of previous positive associations between diet and the availability of supermarkets,³⁴ we hypothesized that the presence of supermarkets would be associated with a lower prevalence of overweight and obesity among the Atherosclerosis Risk in Communities (ARIC) study participants. Because diet and obesity are also associated with other CVD outcomes, we further hypothesized that the presence of supermarkets would also be associated with a lower prevalence of diabetes, hypercholesterolemia, and hypertension.