Grain-based foods 24-hour portion size recall compared to photo portion selection by university students

Abstract

The ubiquity of fast food outlets, the huge increase in restaurant portion sizes at restaurants, and the shift to an auto-oriented, TV-watching lifestyle has resulted in an obesity epidemic caused by societal changes in the 20th century (Nestle and Jacobsen, 2000). From a practitioner’s viewpoint, finding methods that will effectively assist in determining actual food portions will be pivotal to advocating change. Nationwide food consumption surveys employ the 24-hour food recall because of its cost-efficiency, ease of administration and low respondent burden. Food photograph accompaniment may help subjects estimate portion size. Nelson et al. (1994, 649) reported that a process composed of perception, conceptualization, and memory takes place when a photograph is used to identify portion size during an interview and Chambers et al. (2000, 891), described cognitive strategies used by interview respondents when making judgments about portion size. Nelson et al. from the UK (1994, 1996, 1998a, 1998b), extensively examined food photography use in portion size assessment noting the benefits as well as the inaccuracies. Yet, limited research exists from the US querying the errors associated with estimating food portion sizes from photographs. This study utilized the Portion Photos of Popular Foods (3PF) book (Hess 1997) with the purpose of enhancing the validity of dietary assessment methodology by assessing the impact of a photographic aid on portion size recall. Serving sizes reported from a standard 24-hour dietary recall (24R) were compared to those selected using 3PF (the standard). In view of current food intake trends, the research focus was narrowed to the grain group: breads (including mixed foods), cereals and starchy vegetables. Forty-two males (mean age 24 y; average BMI 26.04) and 51 females (mean age 22.7 y; average BMI 23) representing 33 distinct non-nutrition majors completed a 24R interview using standard methods with opportunity for demonstration of size using a ruler. Immediately after 24R, subjects selected the 3PF portion closest to their intake. 3PF and 24R differences were expressed in grams, with distinctions made by the researcher between volume rather than density for fair comparison. Over-, under-, and exact reporting were evenly distributed (Chi sq 4.0, p=.13) and not gender related (Chi sq .57, p=.75). 3PF and 24R portions were identical for 52 recalls, but 78 recalls experienced over 1/3rd portion discrepancy of the 3PF serving, 64% of these being over reported. Out of a possible 37, thirty 3PF grain-based foods were selected by the 93 subjects for a total of 181 comparisons. Eight foods accounted for 61% of the responses (110 total: 106 in female; 75 in male), and included: ready-to-eat cereal, spaghetti, pizza, tortilla chips, bagel, rice, French fries, and pasta salad. Based on recall frequency and reporting direction for these eight foods, spaghetti, pasta salad, tortilla chips, and French fries recalls were inaccurate, accurate for pizza and bagels, and ambiguous for ready-to-eat cereal and rice. Large discrepancies of over 100 grams were noted in both directions (over-, and under-) for spaghetti, and pasta salad. Results advocate for multiple portion-size assessment methods, specifically for amorphous foods. Concomitant photo portion use in 24R may facilitate or deter portion recall, depending on the food. It is clear that photographic portion representations need improvement to allow for food-specific differences.