Both groups were shown fast food menus and asked to choose foods for themselves and their children. One group's menu included the calorie content next to the price for each item. The other did not.
On average, parents whose menus did not list calories chose a meal of about 670 calories Those who did list calories chose a meal with about 100 fewer calories.
But the study suggests that parents don't restrict their own caloric intake.
Experts say an extra 100 calories per day in adults can lead to 10 extra pounds in a year.
The study appears in the new edition of the journal Pediatrics.