Warnings about calorie-packed food which explain how much exercise is needed to run the calories off are more effective than traditional counts, researchers say.
It was found that teenagers who were shown the warnings on fizzy drink cans - which stated an hour's run would be needed to get rid of the calories - were half as likely to drink them.
Researchers from Johns Hopkins University in Baltimore, USA, posted three different signs outside corner shops to see which was best at putting teens off the soft drinks, which contain an average of 250 calories each.
One asked if they knew that the average fizzy drink contained 250 calories, another asked if they knew it was equivalent to ten per cent of their recommended daily intake, while a third asked 'Did you know that working off a bottle of fizzy drink or fruit juice takes about 50 minutes of running?'
Results showed that providing calorie-related information did cause sales to drop by over a third [40 per cent], but that the physical activity equivalent was most effective, reducing soft drink sales among teens by half.
Study author Dr Sara Bleich said: 'People generally underestimate the number of calories in the foods and beverages they consume.
'Providing easily understandable caloric information-particularly in the form of a physical activity equivalent, such as running-may reduce calorie intake from sugar-sweetened beverages and increase water consumption among low-income adolescents.
'Because of the health problems associated with junk food, it is critical to explore the most effective strategies for presenting caloric information to consumers on fast food restaurant menu boards.'
Super sweet fizzy drinks have been blamed for a range of health conditions including obesity, heart disease and type-2 diabetes.
They are most popular among teens and people from poorer backgrounds.