Higher densities of fast-food and full-service restaurants are not associated with obesity prevalence

Abstract

Background: The obesity epidemic in the United States has been mirrored by an increase in calories consumed outside of the home and by expansions in the numbers of, and portion sizes at, both fastfood restaurants (FFRs) and full-service restaurants (FSRs), leading some to blame the epidemic on the restaurant industry. If this were indeed true, one would predict that greater per capita densities of FFRs and FSRs would lead to greater obesity prevalence. Objective: We evaluated the population-level association between both FSRs and FFRs and the prevalence of obesity and calculated the proportion of calories consumed in these establishments. Design: In this ecological cross-sectional study, we used countylevel data (aggregate-level data) for obesity prevalence across the mainland United States in 2012 and matched these data to countylevel per capita densities of FFRs and FSRs in the same year. Multiple linear regression was used to determine the relation between the prevalence of obesity and the densities of FFRs and FSRs after adjustment for confounding factors. Results: Contrary to expectations, obesity prevalence was highly significantly negatively related to the densities of both FFRs and FSRs (combined-effect R 2 = 0.195). This was principally because greater numbers of both FFRs and FSRs were located in areas in which individuals were on average wealthier and more educated. When we normalized for these factors (and additional socioeconomic variables), the associations between restaurant densities and obesity effectively disappeared (pooled R 2 = 0.008). Our calculations showed that the percentage of total calories consumed in FFRs and FSRs is a mean of only 15.9% of the total intake (maximum: 22.6%). Conclusions: Variations in the densities of FFRs and FSRs are not linked to the prevalence of obesity in the United States, and food consumed in these establishments is responsible for ,20% of total energy intake. This finding has implications for policy decisions regarding how we aim to tackle the obesity epidemic.Am J Clin Nutr 2017;106:603-13.

Reply to VI Kraak

“…The direct suggestion is that implementation of such changes would have a tangible impact on US obesity rates. Our analysis, and that of others (1,4), indicates that this may be unduly optimistic and relies more on faith that restaurants are the main issue, rather than any tangible evidence. Even if the total calories per meal were reduced to 700 kcal to meet the recommendations (5), from the current average of 932 kcal at the average fast-food restaurant (1), this 33% reduction in calories per meal would only translate on average to a 2.8% reduction in total calorie consumption at current restaurant visit rates.…”

Association of Fast‐Food and Full‐Service Restaurant Densities With Mortality From Cardiovascular Disease and Stroke, and the Prevalence of Diabetes Mellitus

“…This suggests dietary components linked to CVD and stroke (eg, salt, SFA, and TFA) may have greater levels in FFRs than in FSRs . The negative association between diabetes mellitus prevalence and FSRs was also found with respect to obesity and presumably reflects an unaccounted for confounding factor …”

“…Why FSRs do not associate with CVD and stroke, when FFRs do, is unclear. The energy contents of meals served in FSRs are generally larger than those consumed at FFRs, but they are consumed less frequently, so their contributions to total calorie intake are approximately equal . This suggests dietary components linked to CVD and stroke (eg, salt, SFA, and TFA) may have greater levels in FFRs than in FSRs .…”

“…Each county was identified by the Federal Information Processing Standard code, which is a 5‐digit code that allows counties and county equivalent units to be uniquely identified. Apart from determining the crude association between the dependent factors and the county‐level densities of FFRs and FSRs, we corrected the mortality from CVD and stroke and the age‐adjusted prevalence of T2D for county‐level poverty (percentage in poverty), ethnicity (percentage black), and education (percentage with bachelor's degree or higher), which we have previously established are significant confounding factors for the FFR and FSR densities . We performed stepwise multiple linear regression analyses, including all the potential confounding factors as independent variables (poverty, ethnicity, education, physical inactivity, and smoking) and CVD mortality, stroke mortality, or prevalence of T2D as the dependent variables.…”

“…Consequently, although meals are consumed at FSRs less frequently, calculations suggest that these out‐of‐home calories are contributed to almost equally by both FFRs and FSRs. For example we previously estimated that in the United States, adults, on average, consume 8.6% of their daily calorie intake at FFRs and 7.6% at FSRs . Portion sizes have inflated at both FFRs and FSRs over time, and recent studies have suggested that 32% of FFRs and 22% of FSRs did not meet the guidelines for the nutritional quality of meals served to children .…”