Eating More When Nobody’s Watching
A major pitfall of nutrition research is the difficulty in accurately recording food intakes. All methods have considerable limitations that affect the collection of data and have the potential to lead to under-, over, or misreporting of food consumed, and potentially influence the results and conclusions of nutrition research. I know from my own research that estimations of calorie intake can be somewhat implausible, for example total calorie intakes in people who are obese should in theory be higher than people with a healthy weight as they have a higher body weight that they have to support, yet I saw that their self-reported calorie intake was lower. A research paper by Archer, Hand and Blair recently stirred up controversy in this field when they found that estimations of food intake over the history of NHANES were not plausible for most participants, especially the obese. Two recent publications looked at this problem: one reports on factors that affect under-reporting of food intakes in children and adolescents (Murakami), and the other investigates the use of a micro-camera to record food intakes (Pettitt).
The Murakami publication explored factors that were associated with either under- or over-reporting in children participating in NHANES (2003-2012). Based on physical activity, gender and body weight, the investigators calculated an estimated energy requirement using the Schofield equation. They found that 13% of children and adolescents were under-reporters of energy intake, and 5% were over-reporters. The presence of overweight or obesity increased the likelihood of under-reporting, as did older age of the children.
The Pettitt publication looked at the feasibility of using a microcamera worn on the ear to record food intakes. Five participants recorded all food intake over the 14 day study period. The participants were also instructed to use the camera to record eating sessions for two days during the two weeks. The camera images were used to estimate portion size, exact food type, and speed of eating, with the results from the food diary and camera analyzed with Dietplan dietetics software. Indirect calorimetry was used to measure resting metabolic rate, and physical activity was ascertained via a questionnaire. In addition, the doubly-labelled water method was used to estimate actual metabolic rate at 7 time points during the study.
The authors found that the subjects consumed less than would be expected for their metabolic rate during the entire two-week period. The food diaries showed a significant 500 kcal lower energy intake per day than energy expenditure over the 14-day period. In addition, food intakes were even lower on the two days that the micro-camera were used, in total around 1000 kcal lower, representing around 34% of the estimated energy requirement. However, the energy intake estimated from the microcamera was around 95 kcal higher than what was recorded on participants’ food diaries. Use of the camera appears to be a little more reliable than food diaries alone.
These results are similar to another study in a human nutrition suite in which subjects lived in a specially designed residential suite in which food intakes were recorded both during covert and overt phases of observation. When subjects thought that their food intakes were not being recorded, they consumed around 170 kcal more than if they thought their food intakes were being recorded.
These publications show the difficulties nutrition scientists face with accurately recording food intakes. If mere participation in a dietary study is enough to change food consumption behavior, it is exceptionally difficult to obtain accurate estimations of the normal diet. Innovations such as a microcamera have the potential to more accurately record food intakes. The problem of lower intakes due to study involvement must still be addressed.
Kentaro Murakami and M. Barbara E. Livingstone. Prevalence and characteristics of misreporting of energy intake in US children and adolescents: National Health and Nutrition Examination Survey (NHANES) 2003–2012. British Journal of Nutrition, available on CJO2015. doi:10.1017/S0007114515004304.
Claire Pettitt, Jindong Liu, Richard M. Kwasnicki, Guang-Zhong Yang, Thomas Preston and Gary Frost. A pilot study to determine whether using a lightweight, wearable micro-camera improves dietary assessment accuracy and offers information on macronutrients and eating rate. British Journal of Nutrition, available on CJO2015. doi:10.1017/S0007114515004262.
Edward Archer , Gregory A. Hand, Steven N. Blair. Validity of U.S. Nutritional Surveillance: National Health and Nutrition Examination Survey Caloric Energy Intake Data, 1971–2010. Published: October 9, 2013. DOI: 10.1371/journal.pone.0076632
Bird JK, Ronnenberg AG, Choi SW, Du F, Mason JB, Liu Z. Obesity is associated with increased red blood cell folate despite lower dietary intakes and serum concentrations. J Nutr. 2015 Jan;145(1):79-86. doi: 10.3945/jn.114.199117. Epub 2014 Nov 12. http://www.ncbi.nlm.nih.gov/pubmed/25527662
R. James Stubbs, Leona M. O'Reilly, Stephen Whybrow, Zoë Fuller, Alexandra M. Johnstone, M. Barbara E. Livingstone, Patrick Ritz and Graham W. Horgan (2014). Measuring the difference between actual and reported food intakes in the context of energy balance under laboratory conditions . British Journal of Nutrition, 111, pp 2032-2043. doi:10.1017/S0007114514000154.