Obesity Epidemiology

354 EPIDEMIOLOGIC STUDIES OF DETERMINANTS OF OBESITYneighborhood. While studies examining area-level food store penetration on individual-levelobesity are an important first step, multilevel strategies that incorporate individual behavioralpatterns as effect modifiers are needed. Finally, the temporal direction of the associationmay seem straightforward; however, obese individuals may select neighborhoods with certaintypes of stores, or market research may locate stores in areas where individuals prefer certainfoods (i.e., where demand for their products is high) and/or by obesity prevalence.Fast Food RestaurantsEating away from home has increased dramatically in the United States over the past 25years, which is of concern given that food prepared at home is of a higher quality thanthat consumed while eating out. 96 Fast food restaurants (which often have limited andunhealthy food options) are a popular source of food consumed away from home, butthe high energy density of many foods available in these settings constitutes a significantrisk factor for obesity. 97 Most Americans do not eat fast food daily, but nearly 40% reporteating it one to two times/week. A number of U.S. studies have shown positive crosssectional(and some longitudinal) associations between fast food consumption and poorerdietary practices, including higher total energy intake and higher percentage fat energy;there is somewhat less evidence for decreased consumption of fiber and fruits and vegetables98-100 and obesity. 98,99,101 For example, one study 102 found an association between theconcentration of residents per fast food restaurant and state-level obesity prevalence.There is other evidence demonstrating effect modification in the relation between fastfood restaurants and obesity, in sometimes-unexpected directions. For instance, Jefferyand French 99 found that the number of fast food meals eaten per week was positivelyassociated with BMI among high-income women, but not among low-income women andmen. Another study found that change in the frequency of fast food consumption over 15years was directly associated with changes in body weight in whites, but more weakly inblacks. 101 Given area-level variation in access to fast food as well as individual variationin purchasing power and food preferences, examining the full range of effect modifiersin the association between fast food and obesity is necessary.How to best define what constitutes fast food is not clear—it is almost certain thatboth misclassification and undercounting have occurred. For example, should ethnicfood stores (e.g., Chinese, Indian), pizzerias, and coffee shops that sell baked goods beincluded? Methodological work is necessary to both define food store types and establishappropriate categorization strategies. Finally, as with other food stores, the direction ofthe association may seem mostly uncontroversial, but it is unclear whether fast food storeplacement (which can also be based on neighborhood characteristics) may affect interpretationsdrawn regarding the direction of the fast food-obesity association.We should remember that regular fast food consumption is a reality for manyAmericans; it may also be a functional strategy for those in low SEP groups, who benefitfrom widely available, inexpensive, and highly palatable food (despite its energy density).Public health strategies are already shifting to recommend that individuals purchase themore healthful fast food options that are becoming increasingly available.Neighborhood Influences on Physical ActivityUrban SprawlOver the last quarter century, we have observed a secular shift towards greater urban sprawlin the United States. With increasing longevity and the steady increase in population, urban