Graphic warning labels - which include photos linking sugary drink consumption with obesity, diabetes and tooth decay - may reduce purchases of the beverages, scientists say.
In a field study conducted in a hospital cafeteria, researchers found that graphic warning labels reduced sugary beverage purchases by 14.8 per cent, while text warning labels and calorie labels had no effect.
"Warning labels have been around a long time for tobacco products, but they're a new concept for sugary drinks. Ours is the first study to evaluate the effectiveness of sugary drink warning labels in the field," said Grant Donnelly, an assistant professor at Ohio State University in the US.
Researchers tested three different types of labels - text warnings and graphic warnings about the health risks of sugary drinks, and listings of the caloric value of the drinks - which they displayed near bottled and fountain beverages in a hospital cafeteria in Massachusetts.
Each type of label was tested consecutively, with two-week "washout" periods between each test during which no label was displayed. Over 20,000 beverage sales were recorded during the study.
The findings, published in the journal Psychological Science, showed that during the weeks when the graphic warnings were displayed, the share of sugar-sweetened beverages purchased in the cafeteria declined by 14.8 per cent.
Consumers appeared to substitute bottled water for sugary drinks.
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The average calories per drink sold also decreased during that period from 88 calories to 75. The text warnings and calorie labels did not have a significant effect on beverage purchasing.
The researchers conducted two follow-up studies online. In the first, consumers were asked about how seeing a graphic warning label would influence their drink purchases.
Findings showed that the graphic warnings increased negative feelings toward sugary drinks and prompted increased consideration of health risks over taste.
In the second study, over 400 online participants were asked whether they would support putting the three labels on sugar-sweetened beverages.
When participants were told that graphic warnings were effective at reducing sugary beverage consumption, they were equally supportive of the graphic labels warnings compared to text warnings or calorie labels.
"Sugar-sweetened beverages are the largest source of added sugars in the American diet and reducing intake of these beverages could improve population health," said Laura Zatz, doctoral student at Harvard T H Chan School of Public Health in the US.