In ongoing public health efforts to curb the obesity epidemic, better menu and nutrition labeling is often tapped as a low-cost way to help make the healthy choice, the easy choice. And while the evidence on the effectiveness of such interventions is still emerging, a recent study found that educating young people on the calories in sugar-sweetened beverages did make a positive difference.

Published in the December issue of the American Journal of Public Health, the study focused on an experiment inside six corner stores located near middle and high schools within low-income, predominantly black neighborhoods in Baltimore. (According to the Centers for Disease Control and Prevention, black youth experience significantly higher obesity rates than white children.) To gauge whether providing calorie information changed youth’s purchasing habits, researchers posted one of four randomly assigned, bright-colored signs on beverage cases. The signs read: “Did you know that a bottle of soda or fruit juice has about 250 calories?”; “Did you know that a bottle of soda or fruit juice has about 16 teaspoons of sugar?”; “Did you know that working off a bottle of soda or fruit juice takes about 50 minutes of running?”; and “Did you know that working off a bottle of soda or fruit juice takes about 5 miles of walking?” Altogether, researchers collected data on more than 4,500 purchases made by black adolescents.

The results are very promising. Compared to baseline data (i.e. beverage purchases before the signs were posted), providing any calorie information reduced the number of total beverage calories purchased, reduced the likelihood of adolescents buying sugar-sweetened beverages and reduced the chance of buying a sugar-sweetened beverage bigger than 16 ounces. Specifically, the study found that prior to the intervention, adolescent purchases averaged 149 calories; after the intervention, beverage purchases fell to an average of 121 calories. And what’s really interesting is that researchers found that differences in purchasing behavior continued weeks after the signs were removed. Authors Sara Bleich, Colleen Barry, Tiffany Gary-Webb and Bradley Herring write:

Understanding the potential for environmental interventions, which are increasingly seen as essential for obesity prevention, to motivate reductions in (sugar-sweetened beverage) consumption among groups at high risk of obesity is important. Clinical obesity interventions are not easily accessible to all adolescents, and most adolescents who begin obesity treatment do not complete it, with poor and minority youths at even higher risk for discontinuing treatment.

Regarding the different signs, researchers found that the sign about the miles of walking it takes to burn off a bottle of soda resulted in fewer calories purchased when compared with the sign about teaspoons of sugar and the sign about running. The study also found that after posting the informational signs, the frequency of soda and sports drink purchases were significantly lower. However, purchases of fruit drinks went up, though researchers said the difference was not statistically significantly. Overall, the frequency of not buying a beverage at all was much higher. Also, after the signs were posted in the corner stores, many more youth decided to buy a smaller bottle of sugar-sweetened beverage — before the intervention, 27 percent bought large-volume sodas versus 16 percent post-intervention.

Researchers also conducted exit interviews with a quarter of the sample study, finding that a majority understood the information presented and 40 percent said they changed their purchases after seeing the calorie signs.

“The results related to a reduced quantity of (sugar-sweetened beverage) purchases were consistent with our previous work and another recent study that suggested that presenting caloric information in the form of a physical activity equivalent might be more persuasive to consumers than absolute calories,” researchers wrote. “These findings were also consistent with research that suggested that calorie information reduces calorie ordering and consumption.”

To request a full copy of the study, visit the American Journal of Public Health.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.