Obesity Epidemiology

DIETARY ASSESSMENT METHODS 8524-Hour RecallsThe 24-hour dietary recall involves the collection of detailed information on all foodsand beverages consumed by a subject in the previous day or past 24 hours. This methodis most widely used by national nutritional surveys (e.g., the National Health and NutritionExamination Survey (NHANES), USDA Nationwide Food Consumption Surveys,and the Continuing Surveys of Food Intakes by Individuals) to estimate average intakesof populations. The recall method, especially the unannounced recall (see below), is frequentlyused in dietary intervention trials to monitor adherence. A single 24-hour dietaryrecall can be useful for estimating mean intakes of a population in national surveys, butit alone cannot be used to estimate usual intakes of individuals, or provide correct distributionsfor the population because of large within-person variations in dietary intakes. 3The 24-hour recall is usually conducted by a trained or certified interviewer. Theinterview is often face to face, but can also be done by telephone. In the face-to-faceinterview, visual aids, such as food models or shapes, can be used to obtain moreaccurate information on quantities of foods. To help with portion size estimation in telephone-administeredinterviews, two-dimensional food portion visual aids or photographsare sometimes mailed to the respondents’ homes beforehand. 4 To avoid changes in participants’eating habits, 24-hour recalls are best administered unannounced, that is, notscheduled on a specific day. The surprise aspect of the unannounced telephone interviewis especially important for monitoring compliance in dietary intervention studies. 5Traditional paper-and-pencil or computerized systems can be used to collect datafrom 24-hour recalls. The Minnesota Nutrient Data System (NDS) has been specificallydesigned for conducting real-time interactive interviews 6 and a computer program,EPIC-SOFT, has been developed to standardize interview-based 24-hour recalls in theEuropean Prospective Investigation into Cancer and Nutrition (EPIC) study. 7The multiple-pass 24-hour recall is a method in which interviewers use several(3 or 5) distinct passes or steps (with multiple cues and opportunities for participants)to collect information about a subject’s food intake over the preceding 24 hours. 8 TheUSDA 5-pass method involves five steps. 9,10 The first pass is a quick list of all foodsor beverages the participant consumed in the previous day. The second pass (termedforgotten list) involves a probe of possible forgotten foods, for example, snacks, sweets,and soft drinks. The third pass (time and occasion) asks the subject to describe thetime and situation in which the foods were eaten. The fourth step (the detailed pass)involves probing for detailed information on preparation, ingredients, and portion sizes(use of two-dimensional food models can help subjects estimate portion sizes). The laststep (the fi nal review pass) involves reviewing the recalled information and probing forinformation on any additional food items. The multiple-pass 24-hour recall method has ledto improvement in food recalls. 9,11 However, the approach is still prone to underreportingthat typically occurs with self-reported methods, a problem that involves memory lapsesand difficulties in estimating portion sizes.It is well known that a single 24-hour recall does not represent usual intake or reliablyrank subjects according to nutrient intakes because of large day-to-day variations. Multiplerecalls are required to estimate an individual’s usual diet, however, the optimal number ofrecalls depends on the nutrients or foods of interest; those with large day-to-day variationswill require more recalls than those with smaller day-to-day variations. In large cohort studies,the cost of collecting and processing dietary data from multiple 24-hour recalls is oftenprohibitive. However, it is possible to do so in a subset of the cohort for validation purposes.