I'd have to do WHAT to eat that?

Researchers say that showing people how much activity they'd have to do to burn off certain foods may change their behavior more than showing them the number of calories in each item. Every person's calorie burn is different, but these estimates may make you think twice about your next fast food order.

• Showing how much activity is required to burn off a beverage may help change behavior


• Study authors tested this theory in six stores around Baltimore


• They found activity info encouraged more teens to purchase water or diet soda

(CNN) -- By early next year, more than 20 chain restaurants will be posting calorie counts on their menus. Yet that information may not be enough to change consumers' behavior, researchers say.

According to a new report published in the American Journal of Public Health, the number of calories in a food or beverage item doesn't mean much to many folks. But showing people how much activity they would have to do to burn those calories off might be enough to convince us to ditch our unhealthy habits.

Researchers posted different types of signs around six stores in Baltimore. One type of sign posted the number of calories in a regular bottle of soda. Another type posted the amount of sugar in the same bottle. A third type of sign showed either the number of minutes someone would have to run or the number of miles they would have to walk to burn off those 250 extra calories.

The scientists recorded all the purchases made by their target study population -- black teenagers from 12 to 18. They also asked some of the adolescents what they thought of the signs as they exited the stores.

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Overall, the study author found that providing any calorie information encouraged more teens to purchase water or diet soda instead of a sugar-sweetened beverage. But signs that displayed the physical activity information had a stronger effect than the other types of signs.

"There is a strong scientific link between consumption of sugary beverages and obesity," study author Sara Bleich of Johns Hopkins' Bloomberg School of Public Health Department of Health Policy and Management said in a statement. "Using these easy-to-understand and easy-to-install signs may help promote obesity prevention."