The central aims of this study were to assess the public's knowledge of daily energy requirements and their beliefs about the perceived usefulness of caloric information on chain restaurant menu boards - overall and among subgroups at higher obesity risk. This is the first national poll to assess public beliefs about calorie posting initiatives which require some chain restaurants to post caloric information on menus or menu boards alongside price.
Overall, we found that most Americans were knowledgeable about energy requirements for moderately active men and women, but tended to underestimate energy requirements for inactive adults. Only about half of the public perceived themselves as sufficiently knowledgeable to make lower calorie choices in chain restaurants. Americans expressed a positive attitude towards calorie posting in chain restaurants; a majority viewed it as very or somewhat useful, reported being more likely to eat in a chain restaurant with calories posted in the menu and reported being more likely to select a low calorie food where calories were posted. Given that price, convenience and taste [23, 24] are the major motivators for food purchasing decisions, our finding that Americans were evenly divided between purchasing an item based on calories or price is very encouraging for calorie posting initiatives.
Our findings also suggest that calorie posting initiatives may be more salient among certain sociodemographic groups. Blacks, Hispanics and women, who are disproportionately impacted by obesity , were more likely than their counterparts to perceive calorie posting as very useful, to report they would eat in a chain restaurant with calorie posting and to report that caloric posting would encourage their selection of a lower calorie food. Therefore, mandatory calorie posting initiatives may be more salient among women and racial/ethnic groups.
These results further suggest that the best mode for communicating caloric information in chain restaurants may not be calorie count (e.g., a hamburger is equal to 300 kcal) - the dominant mode of communicating caloric information in chain restaurants to date. Rather the public is pretty evenly divided between three possible presentation formats: number of calories, physical activity equivalent, or percentage of total daily energy intake. Our finding that most Americans favor a mode of communication other than a calorie count is consistent with prior research suggesting that interpretational aids help consumers with nutritional labels . It also may partially explain mixed findings on the impact of calorie labeling on purchasing behavior in New York City; some studies show an impact  whole others show none .
This study makes three important contributions to the evidence base. To our knowledge, this is the first study to assess consumer understanding of overall daily energy requirements and perceived effectiveness of calorie posting in a nationally representative study sample. Previous research has focused on sub-populations and small geographic areas . Second, it identifies groups at higher risk for obesity who are most likely to be positively affected by calorie posting initiatives. Third, the results from this study may inform the recent legislative interest in mandating calorie posting in chain restaurants in the United States and other developed countries.
There are limitations to this analysis which deserve discussion. First, this cross sectional analysis only allows us to address associations. Second, we asked our respondents to think abstractly about how they might use caloric labeling at the point of purchase. Given that individuals are inclined to have an optimism bias - tendency to be overly positive about the outcome of their planned actions  - our results may be somewhat inflated. Third, that the public appeared to have a good understanding of the recommended federal energy requirements for moderately active adults but did not perceive themselves as sufficiently knowledgeable to make lower calorie choice, may be more related to the plethora of dietary guidelines based on the 2,000 kcal diet and less a reflection of true caloric knowledge. Fourth, because the range of calories in the correct response category for the caloric knowledge question was broad, our finding of relatively high caloric knowledge may be biased upwards. Fifth, given that the correct answer to the caloric literacy questions was the same for all groups (e.g., moderately active men, moderately active women and inactive adults), some respondents may have assumed the answer should change across groups. This would bias our results downwards and may partially explain our finding of low caloric literacy about inactive adults. Sixth, we relied on self-reported height and body weight to calculate body mass index which may lead to an underestimation of the obese population . However, research suggests that the self-reported height and body weight bias do not differ by race/ethnicity Seventh, random digit dialing, which was used to capture the study population, omits individuals who rely sole on cell phones or individuals who cannot afford a land line in their home. Finally, that McDonalds and Subway were provided as examples of chain restaurants in the survey questions may have affected respondent views on calorie posting. The direction of the bias would have depended on their perceptions of those chain restaurants.
Despite these limitations, this study has several strengths. It is consistent with state and local efforts in the United States to mandate calorie posting in chain restaurants as well as with the current federal priorities to reduce the prevalence adult obesity [31–33]. Second, it is very timely. Given wide-spread recognition among experts that the obesity epidemic is largely driven by environmental changes [1–3], there is considerable interest in designing effective societal-level interventions which reduce energy. Third, a better understanding of public perceptions about calorie posting may encourage policy makers to adopt this policy tool which is likely low cost, particularly for large food outlets with standard menus. In turn, the likely "calorie shock" about the high number of calories in food options, which has been reported in the mass media, may encourage restaurant chains to highlight lower calorie options and/or introduce healthier options. Some restaurants may also begin voluntarily providing caloric information. For example, YUM! Brands (owners of Pizza Hut and KFC) have announced plans to begin providing caloric information in their 20,000 outlets nationwide by 2011, regardless of legislative requirements.
The results from this study suggest the need for more research in two key areas. First, that a majority of Americans miscalculate the energy requirements of inactive adults (which characterizes most Americans ) suggests a poor understanding of energy balance. Second, more research is needed to understand whether the most effective mode for presenting consumers with calorie information and whether it varies by sociodemographic characteristics.