Impact of sugary drink taxes on beverage calories purchased in a national fast food restaurant chain: A quasi-experimental study

Background: Sugary drink taxes have been implemented in several U.S. jurisdictions, but we know little about the impact of taxes on calories purchased in restaurants. The impact may differ in restaurant (vs. non-restaurant) settings because restaurant consumers may be less likely to travel to other jurisdictions for a single meal, choose no beverage or non-taxed beverages, decrease their beverage size, or order combo meals where the drink is bundled with other items at a single price. Methods and findings: We used six years of transaction-level sales data (2015–2020) from 7,341 Taco Bell restaurant locations to estimate the association of sugary drink policies with beverage calories purchased in the drive-through setting of fast food restaurants over time. Taco Bell restaurants represents a large sample size of data from several U.S. jurisdictions across a long follow-up period, which is unique in the literature. We defined the treatment group as restaurants in five jurisdictions where taxes were ever implemented (Albany, CA; Cook County, IL; Oakland, CA; Philadelphia, PA; Seattle, WA) (n = 60 restaurants). We identified a group of comparison restaurants where taxes were never implemented using synthetic control methods (n = 60 restaurants). We used a difference-in-differences design with calendar month and restaurant fixed effects to compare changes in outcomes between groups between the baseline (3–14 months prior to tax implementation) and 3- to 24-month follow-up periods, overall and by jurisdiction. Our primary outcome measure was beverage calories per transaction, from individually-purchased beverages and combo meals (separately). In the baseline period, average beverage calories per transaction were 51.1 (SD = 8.6) in the tax group and 42.3 (SD = 7.4) in the comparison group; and 119.5 (SD = 15.3) and 115.0 (SD = 23.0) beverage calories per transaction in combo meals. Overall, we observed no association between taxes and changes in beverage calories per transaction between groups during the follow-up period, including from individual beverage items (difference-in-differences = −0.3 (95% CI [−0.8, 1.2]) and combo meals (difference-in-differences = −4.3 (95% CI [−13.5, 5.0]). We observed similar results by location, except in Oakland, CA, where customers purchased 16.8 (95% CI 19.6, 14.1) fewer beverage calories per transaction from combo meals; the association was null after conditioning on the purchase of a beverage (difference-in-differences = −1.01 [−4.93, 2.92)]). The main limitations of our study methodology include the exclusion of beverage calorie data from in-store transactions and that the majority of the restaurants in our sample were located in Cook County. Conclusions: Though we observed differences in certain jurisdictions, overall our findings suggest that sugary drink taxes may not be effective in reducing beverage calorie consumption in fast food restaurants. Why was this study done?: What did the researchers do and find?: What do these findings mean?: In a quasi-experimental study, Pasquale Rummo and colleagues investigate the association between sugary drink taxes and calories purchased from beverages per transaction and jurisdiction, in the drive-through setting of 7341 Taco Bell restaurants based in five USA jurisdictions.