Accuracy of stated energy contents of restaurant foods in a multi-site study

Authors: URBAN, LORIEN - Tufts University; MCCRORY, MEGAN A. - Purdue University; DALLAL, GERARD E. - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; DAS, KAI KRUPA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; SALTZMAN, EDWARD - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; WEBER, JUDITH L. - University Of Arkansas; ROBERTS, SUSAN B. - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Journal of the American Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2011
Publication Date: 8/4/2011
Citation: Urban, L., Mccrory, M., Dallal, G., Das, K., Saltzman, E., Weber, J., Roberts, S. 2011. Accuracy of stated energy contents of restaurant foods in a multi-site study. Journal of the American Medical Association. 306(3):287-293.

Interpretive Summary: The 2010 Dietary Guidelines for Americans emphasize reducing calories consumed as a way to prevent and treat obesity. In the U.S., approximately 35% of daily calories are obtained from restaurant foods; therefore, the use of restaurant stated nutrition information to monitor calorie intake has the potential to play an important role in obesity prevention and treatment. However, the accuracy of provided nutrition information in restaurants is unknown. We therefore conducted a study to examine the accuracy of restaurant stated nutrition information by collecting a random sample of 269 foods from 42 restaurants located in 3 U.S. states. Calories in the restaurant foods were measured in the laboratory using bomb calorimetry and laboratory values were compared to restaurant stated values. On average, the foods contained 10 calories more than stated (confidence interval [CI], -15 to 34) which was not statistically significantly different from a 0 calorie difference (P=0.57), but the difference between stated and measured calories was highly variable. Nineteen percent (n=50) of foods contained >100 calories more than stated, and when we re-sampled the 10% (n=13) of foods with the highest positive percent discrepancy between measured and stated, the average discrepancy in the second sample was nearly as high as the first (+289, 95% CI, 186 to 392 and +258, 95% CI, 154 to 361) calories, respectively; P <0.001 for each vs 0 kcal). In addition, foods with lower stated calories actually contained more calories than stated, while foods with higher stated calories contained fewer (P<0.001). In conclusion, stated calories of restaurant foods were accurate. However, for some individual foods there was substantial inaccuracy, with understatement of calories for those with lower calorie contents.

Technical Abstract: Context National recommendations for prevention and treatment of obesity emphasize reducing energy intake. Foods purchased in restaurants provide approximately 35% of daily energy intake, but the accuracy of information on the energy contents of these foods is unknown. Objective To examine the accuracy of stated energy values of foods purchased in restaurants. Design and Setting A validated bomb calorimetry technique was used to measure dietary energy in food orders from 42 restaurants, comprising 269 total items and 242 unique foods. Restaurants and foods were randomly selected from quick-serve and sit-down restaurants in Massachusetts, Arkansas, and Indiana between January and June 2010. Main Outcome Measure Difference between restaurant-stated and laboratory-measured energy values corrected for standard metabolizable energy conversion factors. Results Stated energy contents were not significantly different from measured values overall (difference in absolute stated vs absolute measured, +10 kcal/portion; 95% confidence interval [CI], -15 to 34; P=0.57), but individual stated values were variable relative to measured values. Nineteen percent (n=50) of foods contained >100 kcal/portion more than stated, and foods initially in the highest 10% for excess energy and available for a second sampling (n=13) contained an average of +289 (95% CI, 186 to 392) and +258 (95% CI, 154 to 361) kcal/portion more than stated in the first and second analyses, respectively (P <0.001 for each vs 0 kcal). In addition, foods with lower stated energy contents contained more energy than stated, while foods with higher stated energy contained less (P<0.001). Conclusion Overall, stated energy contents of restaurant foods were accurate. However, for some individual foods there was substantial inaccuracy, with understatement of energy content for those with lower energy contents.