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Posting calorie information on menus is often cited as an important tool in fighting obesity, but a study published today shows that at least in its initial stages, it doesn’t have as big an effect as many health officials hoped.

California chain restaurants must provide calorie information in a readily accessible place for consumers and, starting in 2011, will have to post the data on menus. Some restaurants are already doing that.

Calorie information on menus may increase awareness of calorie content but has less of an effect on the number of calories people purchase, according to New York University researchers in a study published today by the journal Health Affairs.

Their data are from New York city, where a mandatory posting law for chain restaurants went into effect last year. The study’s authors looked at purchases made by adults at fast-food restaurants two weeks before and one month after mandatory calorie labeling went into effect in July 2008. They focused on lower-income, predominantly black and Latino communities in New York.

Here’s what they found:

• The percentage of people who noticed calorie information increased significantly after the regulation was implemented, from 16% to 54%.
• Nearly 28% of the post-labeling sample who saw the calorie information said the information influenced their choice. Of those, almost 90% said they bought fewer calories in response.
• There were significant increases in the percentage of people who utilized the information (2.5% to 15%) and the percentage who said it made them purchase fewer calories (1.9% to 13%).
• While a significant number of those surveyed said calorie labeling influences their food choices, there were no significant differences in the mean number of calories individuals purchased before and after the regulation was implemented.

According to the Robert Wood Johnson Foundation Healthy Eating Research program, which was one of the funders of the study, eating behavior is notoriously resistant to change.

The foundation said that ‘simply displaying information about the caloric value of various food options may fail to translate into attitudinal, motivational, or -- most importantly -- behavioral changes in line with choosing healthier food options. Menu labels may need to be coupled with additional policy approaches in order to have a significant impact on eating behaviors.’

The report came out on the same day a study in Health Affairs questioned whether a moratorium on new fast-food restaurants in South Los Angeles is effective in fighting obesity. Read The Times report here.

Full versions of both studies can be found here.

-- Jerry Hirsch