Displaying the amount of time you'd need to jog in order to burn off the calories from a sugary drink, rather than showing a calorie count, may be more effective in dissuading you from consuming those beverages, new research suggests.
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Researchers observed teenagers at stores in West Baltimore, where signs displayed either calorie counts, calorie counts as a percent of recommended daily calorie intake, or the time spent jogging that would be needed to burn off those calories. While all led teenagers to purchase fewer sugary beverages, the conversion to exercise minutes was the most effective.
"In general, people are very bad at estimating the amount of calories in food they consume," said study researcher Sara Bleich, an assistant professor of health policy and management at Johns Hopkins's Bloomberg School of Public Health. "If we give them easy ways of examining it…I think we can be effective in reducing calories in purchases."
After introducing the signs to neighborhood stores near schools, researchers observed teenagers and monitored how their beverage-purchasing habits changed compared with the period before the signs went up.
About 93 drinks a day were purchased in each store, on average, and this number declined slightly when the signs went up. Soda sales, which made up almost half of all purchases, dipped slightly, as did those of iced tea and sports drinks. However, sales of non-sugary beverages increased, especially sales of water, which went from 5 to 10 drinks sold daily, on average.
While all three types of signs seemed to reduce the number of sugary drinks that were bought, only the signs displaying exercise times had results strong enough to mean researchers knew the decrease in purchases could not be due to simple chance.
250 calories, or a 40-minute jog?
Researchers calculated the exercise times based on a 110-pound teenager, and jogging was chosen because many people don't like to do it, Bleich said. Exercise times, she noted, would vary depending on a person's weight. For example, a 110-pound person would need to jog for 50 minutes to burn off a 20-ounce bottle of soda, whereas a 150-pound person would need to jog for 40 minutes.
Some stores chose not to participate; their reasons included a language barrier and a fear of losing sales. Bleich said the sales issue may be an obstacle going forward, but the study offered some reassurance, as students bought more water when the calorie signs went up.
Bleich said they chose to study black teenagers because they are one of the groups with the highest levels of obesity, and tend to have lower levels of health information. A wider study is planned that includes Hispanic teenagers as well, she said.
Calorie counts soon to appear on more menus
If the results hold, the study may have a wider-reaching impact.
"It was a very interesting study, and I think most Americans would be floored to learn it takes 50 minutes to burn off one 20-ounce bottle of soda, basically a nutritionally worthless beverage," said Julie Greenstein, deputy director of health promotion policy at the Center for Science in the Public Interest, a health and nutrition advocacy group.
"I think there'd have to be some further studies on that to see if there would be an impact," Greenstein said. "If it does have an impact, the federal government should consider this on a broader scale.
"Sometimes other messages are more beneficial to reducing consumption. I think it makes sense to focus on sugary drinks, since they are the largest single source of calories."
Bleich said that was one reason the study focused on beverages. With a mandate for calorie counts in larger restaurant chains coming next year, she said it is important to find a way to convey that information in a way the consumer understands.
While the current study was in black teenagers, Bleich said this means of conveying the information may work even better in other demographics.
"My sense would be if you did this sort of study in a group of people for whom nutrition or fitness might be more important, you might have a bigger effect," she said. "If you're more interested in changing your behavior, you're more likely to pay attention to this sort of information."
The study appears in the Dec. 15 edition of the American Journal of Public Health.