Researchers looked at six years of soda sales data from Taco Bell restaurants in five U.S. cities that added taxes on sugary drinks. They compared what people bought in cities with the tax to similar cities without the tax. Surprisingly, the taxes didn’t seem to reduce the number of calories people purchased from drinks. The only exception was Oakland, California, where people bought slightly fewer calories from drinks in combo meals. This suggests that taxing sugary drinks might not work as well in fast food restaurants as some people hoped, possibly because customers can’t easily go elsewhere for a quick meal.
The Quick Take
- What they studied: Whether taxes on sugary drinks actually reduce the calories people buy from beverages at fast food restaurants
- Who participated: 120 Taco Bell restaurant locations (60 in cities with soda taxes and 60 in cities without taxes) tracked from 2015 to 2020. The taxed cities were Albany and Oakland, California; Cook County, Illinois; Philadelphia, Pennsylvania; and Seattle, Washington.
- Key finding: Overall, soda taxes did not reduce the calories people purchased from drinks. People bought about the same amount of beverage calories whether or not there was a tax. Only Oakland showed a small reduction in combo meal drink calories.
- What it means for you: If you live in a city with a soda tax, the tax alone may not automatically make you drink fewer calories. You might still need to make a conscious choice to pick lower-calorie drinks. However, this study only looked at fast food drive-throughs, so results might be different at grocery stores or other restaurants.
The Research Details
Researchers used a clever method called “difference-in-differences” to compare what happened in restaurants before and after taxes were introduced. They looked at actual sales data from Taco Bell’s computer systems over six years (2015-2020), which gave them real information about what people actually bought, not just what they said they bought.
They created two groups of restaurants that were very similar at the start: one group in cities that added soda taxes (60 restaurants) and one group in cities that never added taxes (60 restaurants). By comparing how each group’s purchases changed over time, they could see if the tax itself made a difference, rather than other factors like population changes or new menu items.
This approach is stronger than just looking at one city before and after a tax, because it accounts for changes that might happen anyway over time.
Fast food restaurants are different from grocery stores or regular restaurants because people often go through the drive-through for a quick meal and might not be willing to travel to another city just to avoid a tax. This makes fast food a good place to test whether taxes actually change what people buy. The study used real sales data rather than surveys, which is more reliable because it shows what people actually purchased, not what they remember buying.
This study has several strengths: it used six years of actual transaction data from over 7,000 restaurant locations, which is a large amount of real-world information. The researchers carefully matched comparison restaurants to make fair comparisons. However, the study only looked at drive-through purchases, not people eating inside the restaurant, so it might miss some sales. Also, most of the restaurants studied were in Cook County, Illinois, which might make the results less representative of other areas.
What the Results Show
When researchers looked at all the data together, soda taxes did not reduce the calories people bought from individual drinks. People purchased about the same number of calories whether or not there was a tax. The difference was so small it could easily be due to chance.
For combo meals (where a drink comes bundled with food), the results were similar. People bought about the same amount of drink calories in combo meals in taxed cities as in non-taxed cities.
When the researchers looked at each city separately, most showed no change. However, Oakland, California was different. In Oakland, people bought about 17 fewer calories from drinks in combo meals after the tax started. But when researchers looked more carefully at whether people actually ordered a beverage at all, this difference mostly disappeared.
Overall, the findings suggest that simply adding a tax on sugary drinks doesn’t automatically make people buy fewer calories from beverages at fast food restaurants.
The study found that in the baseline period (before taxes), people in the taxed cities actually bought more beverage calories on average (51 calories per transaction) compared to non-taxed cities (42 calories per transaction). This difference existed before the taxes were even introduced. In combo meals, both groups bought similar amounts of calories from drinks at the start (about 115-120 calories per transaction).
Previous research on soda taxes has shown mixed results. Some studies in grocery stores found that taxes do reduce sugary drink purchases, but this study suggests the effect might be weaker or different in fast food restaurants. The difference could be because fast food customers are in a hurry and may not think as much about the price, or because they can’t easily go to another restaurant for a quick meal. This study adds important information by looking specifically at restaurants rather than just stores.
This study only looked at drive-through purchases, so it missed people who ordered drinks inside the restaurant or at the counter. The study also focused heavily on Cook County, Illinois, which had many more restaurants than the other cities, so the results might be more influenced by what happened there. The researchers couldn’t see what happened with drinks bought at other restaurants or stores, so they don’t know if people switched to buying drinks elsewhere. Finally, the study ended in 2020, so it doesn’t show what might happen over many years as people get more used to the tax.
The Bottom Line
Based on this research, soda taxes alone may not be enough to reduce calorie intake from sugary drinks at fast food restaurants. If you want to drink fewer calories, you may need to actively choose lower-calorie options like water, unsweetened tea, or diet drinks, rather than relying on the tax to discourage you. A tax might help a little bit, but it’s not a complete solution. (Confidence level: Moderate - this is one study focused on one restaurant chain)
This research matters to people who live in cities with soda taxes and want to understand whether the tax is working. It’s also important for city leaders deciding whether to add soda taxes. However, this study only looked at fast food drive-throughs, so the results might not apply to grocery stores, regular restaurants, or other settings. If you rarely eat at fast food restaurants, this study may be less relevant to you.
The study looked at changes over 3 to 24 months after taxes started. If a soda tax were going to reduce drink calories, researchers would expect to see changes within this timeframe. The fact that they didn’t see much change suggests that if taxes do work, it might take longer, or the effect might be very small.
Want to Apply This Research?
- Track your beverage choices at fast food restaurants for two weeks: record the type of drink (regular soda, diet soda, water, etc.) and estimated calories. This helps you see your actual patterns and whether you’re making conscious choices about calories, regardless of whether there’s a tax.
- Instead of relying on a tax to reduce calories, set a personal goal: choose a lower-calorie drink option (water, unsweetened tea, or diet drinks) at your next three fast food visits. Log each choice in the app to build awareness and track your progress.
- Create a monthly check-in to review your beverage choices at restaurants. Compare your average calories from drinks month-to-month. This helps you see if you’re making healthier choices over time, independent of taxes or prices.
This study examined soda tax effectiveness at one fast food restaurant chain and may not apply to all restaurants, grocery stores, or other settings. The findings suggest taxes alone may not reduce drink calories, but this doesn’t mean taxes are ineffective for other health goals or in other contexts. If you have concerns about your sugar or calorie intake, speak with your doctor or a registered dietitian for personalized advice. This research is one study and should not be the only factor in making health decisions.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.