Writing about their findings in a paper published online in the journal Appetite on 7 December, researchers from the University of North Carolina (UNC) said it was giving the physical activity information as miles of walking rather than minutes of walking that was more often tied to healthier meal choices.
They also reported that the vast majority of the 802 participants (82%), all women in middle-age recruited through a UNC employee newsletter, said they preferred to see physical activity based menu labels rather than labels with calorie information alone or no nutritional information.
For the study, which used a web-based survey to gather information on the participants' choices, the researchers randomly assigned them to one of four groups, each given a different menu:
- A menu with calorie information,
- A menu with calorie information and the minutes of walking required to burn off those calories,
- A menu with calorie information and the miles of walking required to burn off the calories, and
- A menu with no nutritional information (the control group for comparison).
The options on offer included burger meals, sandwiches, sides, salads, dressing, desserts and drinks. The menu was compiled from online menus of common fast food restaurants in the US, without pictures.
One of the options was a regular burger containing 250 calories that would take 78 minutes or 2.6 miles (4.2 km) of walking to burn off.
The results showed a significant difference in the average number of calories ordered based on menu type.
The group that had menus with no nutritional information ordered on average 1,020 calories, compared with 927 calories in the group that had only calorie information, 916 calories in the group given calories and minutes of walking, and 826 calories in the group given calories and miles of walking information.
The authors write:
"The menu with calories and the number of miles to walk to burn those calories appeared the most effective in influencing the selection of lower calorie meals (p = 0.0007) when compared to the menu with no nutritional information provided)."
However, they add:
"Whether these labels are effective in real-life scenarios remains to be tested."
At the end of the survey, all participants were asked about which type of information they would prefer to see on a menu. 45% said they preferred menus with calories and minutes of walking, 37% said they preferred calories with miles of walking, 13% said calorie information only, and 5% said they preferred menus with no nutritional information.
Putting all the groups together, the results showed that 82% of participants preferred menus that showed physical activity (either minutes or miles of walking) over menus that showed only calorie information or no nutritional information at all.
An interesting feature of the study was that the researchers also inserted questions in the survey designed to test respondents' numeracy: only 31% answered all them correctly, and only 8% answered correctly the ones that were specifically about calories.
This might indicate that numerical information on calories may not be understood by most of the participants (which is somewhat surprising given that 96% of them were educated to college or university level).
Such a statistic is likely to vary with different population groups, but it is one that perhaps policymakers should bear in mind when deciding how to express nutitional information on food labels.
Perhaps it is easier to imagine oneself physically walking a certain distance than trying to work out how much percentage of one's recommended daily calorie limit a particular menu item represents.
As the Christmas holidays approach, this report might encourage more of us to imagine how many miles we may have to walk to burn off all the festive calories we consume.
One recent study suggests that we can help ourselves maintain a healthy weight over the festivities not only by avoiding classic holiday sweets such as cookies or candy, but also by reducing car travel, which apparently is as effective as cutting calories.
Written by Catharine Paddock PhD