Since the introduction of nutrition information on menus, numerous studies have tried to determine if providing calorie counts has had an effect on diners' choices.

New federal guidelines on menu labeling won't be finalized until the end of March, but researchers are eager to find out if the friendly reminders have patrons choosing differently.

Most recently a study looked at a Taco Time chain in Seattle. Researchers found customers' orders were not influenced by calories on the menu.

David Sarwer, clinical director of the University of Pennsylvania's Center for Weight and Eating Disorders, said the preliminary studies only look at a short-term choice.

“The evidence on whether or not this has worked and made a difference will really reveal itself when we begin to see, and hopefully see, a decline or leveling off in the rate of obesity in our country,” he said.

Sarwer, who said people need to see messages repeatedly to change behavior, said it may be some time before it's possible to tell if the messages make a difference.

Amy Auchincloss. with Drexel University's School of Public Health, said most studies look at a consumer’s choice. She said there should be more focus on consumer awareness.  Auchincloss would also like to see a study on whether industries are changing default food choices in response to the regulations.

“As much as we can reduce the decisions the consumers have to make to choose healthy foods and just have the default option be healthier, it will be a win-win for the consumers and, in some ways, for the restaurants as well,” she said.