Americans continue to eat fast food at an alarming rate, likely playing a role in the rise in obesity, heart disease, and diabetes. As suggested by the words “fast” and “food,” time scarcity is one of the strongest predictors of fast-food consumption. Yet despite many studies showing a strong correlation between time scarcity and food choice, it is challenging to estimate the causal relationship—that is, how much time constraints cause people to eat fast food. With time scarcity also correlated with other personal circumstances that determine food choices, such as income, occupation, and family composition, inferring whether more valuable time leads to more fast-food visits is difficult.
We address this question by linking detailed data from Los Angeles on the amount of time people spend in freeway traffic congestion (from highway traffic monitors) with foot-traffic data on visits to food stores (from smartphone GPS data). Using freeway congestion as a measure of time scarcity is advantageous for several reasons. First, traffic has a heavy influence on individual time constraints. Pre-pandemic, drivers were spending more time on the road than ever before, averaging nearly an hour per day, and numbers have climbed back to similar levels recently. Second, analyzing fluctuations in traffic congestion allows us to use plausibly random changes in traffic levels to isolate the effect of time lost on store choice. In short, our study observes which stores consumers visit in response to random local traffic shocks that eat up their time—which might lead them to change their eating habits.
On days when highways are more congested, people are more likely to visit fast-food restaurants and less likely to grocery shop. The effects are particularly pronounced for weekday afternoon rush hour traffic, suggesting that our effects are operating through time constraints at mealtimes. Additionally, traffic delays have no impact on past and future store visits, suggesting that people are not simply changing the day they eat out in response to (or in anticipation of future) traffic.
These results are concerning from a public health standpoint. Eating out—and fast food in particular—tends to be higher in fat, sodium, and energy density, and lower in whole grains, fruits, vegetables, and nutrients than food consumed at home. Prior research estimates an increased intake of 134 calories for meals eaten away from home relative to eating at home. Using this number together with our results, an increase in time spent in traffic from a day that is at the 16th percentile of slowness to one at the 84th percentile would lead drivers to gain an additional 0.2 lbs per year. To put this in perspective, this increased avoirdupois—body weight—is equivalent to 10% of what the average American adult gains in a year. The caloric implications of time lost from traffic congestion on eating habits is substantial.
Overall, our results suggest that policies aimed at loosening time constraints would help battle unhealthy eating habits. For example, improvements in infrastructure to mitigate traffic congestion, or expanding and speeding up public transport, could reduce fast-food dependency. Increasing work-from-home opportunities and reducing the number of days workers go into work could also have a significant impact.
© Panka Bencsik, Lester Lusher, and Rebecca L. C. Taylor
Panka Bencsik is Assistant Professor in the Department of Medicine, Health, and Society at Vanderbilt University.
Lester Lusher is Associate Professor of Economics at the University of Hawaii at Manoa and a Research Affiliate of IZA.
Rebecca L. C. Taylor is Senior Lecturer in the Faculty of Economics at the University of Sydney, Australia.
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