The good news is, most consumers who do read calorie counts take them into consideration when deciding what to order.
"Restaurant food tends to have many more calories than people realize, and many more calories than if the same food is cooked at home whether because of the preparation method or because restaurants often provide large portion sizes," Katherine Bauer told Reuters Health in an email.
Bauer, from the Center for Obesity Research and Education at Temple University in Philadelphia, was not involved with the new study.
Some U.S. cities, including New York, require chain restaurants to post calorie counts for diners. As part of the 2010 Patient Protection and Affordable Care Act, chains with at least 20 locations nationwide will have to list nutrition information on their menus.
"Ideally we hope that restaurant patrons see the calorie information posted at fast food and other restaurants and choose a meal with fewer calories. So far, the evidence is really mixed about whether that actually happens," Bauer said.
The new study was led by Holly Wethington from the National Center for Chronic Disease Prevention and Health Promotion, part of the Centers for Disease Control and Prevention in Atlanta, Georgia.
She and her colleagues used the 2009 national HealthStyles survey, which assessed people's health-related attitudes, knowledge and behaviors.
They analyzed responses from 4,363 participants about whether they had read calorie information at fast food and chain restaurants, and if they had, how they used that information.
Over half of the respondents said they went to fast food or chain restaurants less than once a week. Ten percent reported going three or more times per week, and another 10 percent said they never went to those restaurants.
About 36 percent of people who saw calorie information at chain restaurants read it. Of them, 95 percent reported using the information at least sometimes, according to findings published in the Journal of Public Health.
Respondents who went to fast food and chain restaurants three or more times per week were less likely to read calorie counts than those who went less often. Women were more likely to read calorie counts than men.
It's not clear whether the way consumers use nutrition information would have changed since 2009, Bauer said.
"When people have looked at specific cities like New York, Seattle, and Philadelphia, awareness of the calorie labels increased quite a bit from before calories were required to be posted in those cities," she said.
"However, with the exception of the Seattle study that saw decreases in calories purchased among women and from coffee shops, these studies haven't seen any changes in calories purchased before and after menu labeling laws went into effect."
Bauer hopes having calorie information posted may motivate restaurants to provide more healthy options. Her own research has suggested fast food restaurants are offering more salads and other low-calorie side dishes than in the past.
"The combination of having more low-calorie options and having calories posted could be beneficial for consumers who are calorie conscious but also eat out frequently," Bauer said.
"More and more restaurants are posting nutrition information, including calorie content, so consumers can ask the restaurant staff for this information to see what is in the foods sold," Wethington told Reuters Health in an email.
"Using this information can help consumers select choices that are tasty and satisfying yet perhaps with a few less calories to help manage overall daily caloric intake," she said.
"Balancing daily energy intake with regular physical activity can help manage weight. Knowing how calorie information is used can help us better understand whether nutrition education (such as in high school) could be useful and the types of messages regarding calories that are most helpful at the point of purchase," Wethington said.