Chain restaurants in the United States are now required to put calorie information on their menus, but is this information really influencing what people order?

A new study from Seattle suggests people are paying attention to calorie postings — the percentage of people in the area who said they used the calorie information on restaurant menus tripled in the years after the labels became mandatory in the region.

Researchers analyzed information from more than 3,000 people living in King County, Washington, (which includes Seattle), an area that in January 2009, started to require chain restaurants to post calorie information on their menus. (Some restaurants in the region had voluntarily posted calorie information before that date.)

Participants were surveyed between mid-2008 (before the menu label policy went into effect) and December 2010. During this period, the percentage of people who said they read the calorie information at restaurants increased from 18.6 percent to 59.4 percent, and the percentage who used this information to decide what to order increased from 8.1 percent to 24.8 percent, the study found. Women and people with high incomes were more likely to use calorie information at restaurants, compared with other groups.                                                                         

"These findings suggest that mandatory menu labeling contributes to improving consumer awareness and use of nutrition information," the researchers wrote in the Jan. 20 issue of the American Journal of Public Health.

"The next step is to ensure that all populations are equally aware of and able to use this information," Roxana Chen, a social research scientist at the county's public health office, said in a statement. [Here Are the Healthiest Chain Restaurants in the US]

The findings agree with previous research that has shown that people see and use calorie information when it's posted at restaurants. The new study also found that most of the increase in the percentage of people using the information occurred during the first year after the labeling requirement went into effect.       

The study provides "proof of principle" that if restaurants put calorie information on their menus, people will see it, which is the first step toward improving customers' choices, said Dr. Jason Block, an assistant professor and associate director of the Obesity Prevention Program at Harvard Medical School, who was not involved in the study.

However, the researchers did not have information on what the participants ate, so the study could not determine whether people actually consumed fewer calories after they read the calorie labels at restaurants. Previous studies on this question have been mixed — with some studies conducted in lab settings finding that people make different choices when they're shown calorie information, while other studies conducted in real restaurants have usually failed to find such an effect, Block said.

"Whether people are actually changing what they order [based on calorie labels] is still not clear," Block told Live Science. One previous study, also conducted in King County, did find that, in certain restaurants, people who used nutrition information on menus purchased meals containing up to 143 fewer calories than people who did not use the labels.

And even if people don't make better choices based on calorie labels at restaurants, the labels still may help by educating people about calories, Block said. "If people start to have a better conception of how many calories are in the foods that they eat, then it might help them, if they want to, to make better choices across the board."

Because new the study was conducted in just one county in Washington, the findings may not necessarily apply to other areas.

In November last year, the Food and Drug Administration released the final rules that will require restaurants and vending machines with more than 20 locations to provide calorie information to consumers. Restaurants will have one year to comply with the new rules.

Having to post calorie information at a national level might push more restaurants to reformulate their foods to have fewer calories, Block said.

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