摘要：Objectives. We examined whether physical proximity to supermarkets or supermarket price was more strongly associated with obesity risk. Methods. The Seattle Obesity Study (SOS) collected and geocoded data on home addresses and food shopping destinations for a representative sample of adult residents of King County, Washington. Supermarkets were stratified into 3 price levels based on average cost of the market basket. Sociodemographic and health data were obtained from a telephone survey. Modified Poisson regression was used to test the associations between obesity and supermarket variables. Results. Only 1 in 7 respondents reported shopping at the nearest supermarket. The risk of obesity was not associated with street network distances between home and the nearest supermarket or the supermarket that SOS participants reported as their primary food source. The type of supermarket, by price, was found to be inversely and significantly associated with obesity rates, even after adjusting for individual-level sociodemographic and lifestyle variables, and proximity measures (adjusted relative risk = 0.34; 95% confidence interval = 0.19, 0.63) Conclusions. Improving physical access to supermarkets may be one strategy to deal with the obesity epidemic; improving economic access to healthy foods is another. Access to food sources within the built environment can exert a powerful influence on diet quality, body weight, and other health outcomes. 1–10 Inequitable access to healthful foods, in particular, is thought to be one root cause of the obesity epidemic. 11,12 In many studies, people living in low-income or minority communities were reported to be at greater distance from full-service supermarkets and from grocery stores selling healthful foods. 13–22 Lower income census tracts had fewer supermarkets compared with wealthier areas. 20,23,24 African Americans were less likely to live in census tracts with a supermarket compared with Whites. 4,25 In other studies, closer proximity to full-service supermarkets was associated with healthier eating, lower body mass index values, and with lower rates of obesity and diabetes among adults. 1–5,7,26–30 Studies on obesity and access to healthful foods were based, for the most part, on 2 underlying assumptions. The first assumption was that full-service supermarkets were most likely to offer healthful foods at affordable prices. 7,12 Consequently, full-service supermarkets were clearly distinguished from fast-food outlets and convenience stores. 3,4,7,10,16,18,31,32 It may also be helpful to differentiate supermarkets further by food quality or food price. 33–36 The second assumption was that most people shopped for food either at the nearest food store or in their own neighborhood or census tract. Physical distance to the nearest supermarket became the principal measure of access to healthful foods. The density of supermarkets or other food stores in a given area was then linked with measures of diets and health in the same area. 7,11,27,31,36 Some studies employed more realistic street network distances to calculate the distance between the participant's home and the nearest supermarket. 37–41 To our knowledge, a study from Newcastle, United Kingdom, was the only observational study that collected data on food retail access—distance to the food shops, food availability, and price—and examined these in relation to socioeconomic status (SES), diets, and health. 35,36 The present Seattle Obesity Study (SOS), was the first US-based study to collect data on supermarkets, SES, and health, advancing the field in 3 important ways. First, the geocoding of study participants’ home addresses and the locations of their principal food sources, as obtained from a telephone survey, allowed for the calculation of network distances between the participants’ homes, the nearest supermarket, and the supermarket that study respondents actually shopped at. Second, supermarket chains were stratified into 3 price levels based on the average cost of the market basket of 100 representative foods. The stratification of supermarkets by price allowed for the novel reconceptualization of access to healthy foods both in terms of physical proximity and economic access as determined by supermarket price. Third, the SOS was the first study to collect all data at the individual level, eliminating potential bias because of geographic aggregation. The goal was to determine whether supermarket proximity or price would be more strongly associated with obesity rates, adjusting for individual level demographics, education, and income. In previous studies, obesity was linked to the consumption of low-cost, energy-dense foods. 42,43
