By mid-2012, coffee shops and burger joints across the country will be required to prominently display nutritional information about their food products. Many of the larger franchises are already doing this. But does knowing the number of calories in a caramel latte make you more likely to choose a fat-free coffee?

Unfortunately, no—most studies have found that caloric signage has little or no impact on the food choices that customers make. But that may be because people don’t have a clear idea about what those calories mean, suggests Sara Bleich, a health policy expert at Johns Hopkins Bloomberg School of Public Health.

“When my husband eats junk food, he always says he’ll burn it off later,” Bleich says. “And I’m thinking, ‘No you won’t, honey.’ ”

The 250 calories in a bottle of soda may not sound like much, but to work off those calories, a 15-year-old weighing 110 pounds would have to jog for 50 minutes, ride a bicycle for 73 minutes, or walk briskly for two hours. Adults would have to work even harder, to compensate for their slower metabolism. In a recent study published in the American Journal of Public Health, Bleich found that translating calories into a physical activity equivalent can help customers make healthier choices.

Bleich’s team posted nutritional information on the beverage coolers of three Baltimore corner stores. In each store, the signs held one of three messages:

"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 10% of your daily calories?"

"Did you know that working off a bottle of soda or fruit juice takes about 50 minutes of running?"

The researchers then watched to see whether the signs had any impact on the types of drinks bought by African American teenagers, who are at higher risk for obesity than white teenagers, and who also tend to drink more sugary beverages. In the store whose signs provided the physical activity equivalents, a black teenager’s odds of buying soda or other sugary drinks was halved, as compared to before the signs were posted. The other two treatments—listing the raw calorie count or percent of daily intake—also appeared to decrease the consumption of sugary beverages, but the effects were not statistically significant.

The results are still somewhat preliminary, since the study only looked at one store for each type of sign. Future studies will determine whether the physical activity signage will have similar effects in other populations. Still, Bleich thinks that it may be time to start thinking about alternatives to plain old calorie counts.

“There is a great window of opportunity right now,” she says, because the legislation that will require fast food chains to post calorie counts does not specify exactly how that information should be presented. Of course, it would be difficult for a Starbucks to put a statement like “It takes x hours of bicycling to work off this drink” next to every beverage on its menu, but Bleich says that they could add the signage elsewhere, such as next to its baked goods. Customers could then extrapolate that information to their other menu choices.

No matter how illustrative the presentation, it will take more than a calorie count to help customers make healthy decisions at fast food restaurants. “Posting nutritional information has the greatest effect on people that are interested in making behavioral changes—people who want to lose weight or who care about nutrition,” Bleich says.

Image Credit: Flickr/ironchefbalara