By Julie Watts

(CBS SF) — Love it or hate it,  the calorie information posted at many chain restaurants and fast food joints is having an impact.

A first-of-its kind study by the Centers for Disease Control finds that six-out-of-ten diners who are aware of calorie counts take them into consideration when placing their order. And of those who do take them into consideration, most end up ordering less – according to some studies, between 100 and 400 calories less  than diners who aren’t presented with calorie information.

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“Those who actually see menu labeling actually purchase fewer calories,” said study author Dr. Seung Hee Lee-Kwan of the Centers of Disease Control. “It’s going in the right direction.”

But some say it’s too small a step. “It’s doing some good, but it’s not quite solving the problem,” according to Registered Dietitian Norae Ferrara.  Ferrara says most restaurant meals are just too caloric for normal individuals,  who are supposed to consume between 1,500 and 2,400 calories a day depending on their level of activity. “Even when people pay attention,  they’re still overeating (in restaurants.)”

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And right now, calorie information may be incomplete or missing at some restaurants that were required to have it.

Back in 2009, California passed a first-in-the nation law requiring restaurants with 20 or more locations in the state to post nutritional information.   But right now,  California isn’t actively enforcing the rules.  That’s because federal regulators are currently writing national food labeling provisions that will take the place of California’s provisions.

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A spokeswoman for the F.D.A. says the agency is now putting the final touches on the national rules.