Posting calories on menus has little effect on what customers buy, according to a recent study.

Customers at TacoTime (a western Washington chain) who read how many calories are in their chimichangas, burritos and tacos on the restaurant's menu were just as likely to order them as people who don’t have that information.

For 13 months, researchers recorded food purchases at seven suburban TacoTimes and seven inside Seattle, Washington. Seattle passed a law requiring that all fast food chains post their calories, fat and sodium content to the menus in 2009.

Once the law went into effect, public health researchers in Seattle and researchers from Duke-National University of Singapore Graduate Medical School compared what people were buying at TacoTimes inside and outside the city.

Contrary to their hypothesis, “We found no difference,” said lead author Eric Finkelstein. “We looked at the variables – the transactions, total calories per transaction, food, dessert, entrees. We weren’t able to find any effect whatsoever.”

The findings suggest that having calorie information did not change public health behavior.

This may not be totally surprising. After all, obesity rates have continued to soar after pre-packaged foods were required to carry nutritional content, said Finkelstein, an associate professor of health services at Duke-National University of Singapore.

Similar studies about calorie counts in menus have found either small, marginal effects or no difference at all.

“This is just one chain, so it’s possible to find more compelling results in different chains,” Finkelstein said, about the TacoTime’s study.

Regardless, nationwide changes are coming. The health care reform bill, passed last year, requires fast food chains to post their nutritional information on menus. The FDA’s rules on for this are due in March.

While calorie info on menus may not unleash widespread weight loss, it could have some benefits, Finkelstein said.

“My sense is that if these laws are to have an effect, it’s going to be on the supply side,” he said, referring to fast food companies. “If they’re embarrassed about 2,000-calories lunches, they might try to skimp on calories, sodium and fat.”