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United States Department of Agriculture

Agricultural Research Service

Title: A New Portion Size Estimation Aid for Wedge-Shaped Foods

Authors
item Godwin, S - TENNESSEE STATE UNIVERSIT
item Chambers Iv, E - KANSAS STATE UNIVERSITY
item Cleveland, Linda
item Ingwersen, Linda

Submitted to: Journal Of The American Dietetic Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 2006
Publication Date: August 1, 2006
Citation: Godwin, S., Chambers IV, E., Cleveland, L., Ingwersen, L. 2006. A new portion size estimation aid for wedge-shaped foods. Journal of the American Dietetic Association. 106:1246-1250.

Interpretive Summary: Data from national food consumption surveys have many important uses, such as monitoring the nutritional adequacy of American diets, evaluating programs and policies, and developing Federal nutrition guidance, so it is critical that the data be accurate. Portion size estimation is a potential source of error in data collection. Few studies, however, have been conducted to develop and test portion size estimation aids that can help people accurately report amounts of foods they eat. Many foods eaten in the United States are wedge-shaped (e.g., pizza, cakes, and pies), and these foods may affect intake of nutrients such as saturated fat and sugar that are associated with degenerative health conditions. However, it is difficult for people to estimate portion sizes of wedge-shaped foods. In this study, 320 respondents 18 to 65 years old estimated the portion size of different sizes of pizzas, cakes, and pies using both a ruler and a newly developed aid called an adjustable wedge. Results suggested that the adjustable wedge may be an effective substitute for a ruler in the estimation of wedge-shaped foods. This is based on findings that the adjustable wedge generally was as accurate as or more accurate than a ruler, and that it promoted greater confidence among respondents in their estimates. This research on portion size estimation aids will help improve the collection of food data in surveys, and benefit researchers who analyze and use survey data.

Technical Abstract: The foods consumers eat come in a vast array of sizes and shapes. Many popular foods eaten in the United States are wedge-shaped (e.g., pizza, cakes, and pies), and these foods may affect intake of nutrients such as saturated fat and sugar that are associated with degenerative health conditions. Thus, it is important that amounts of wedge-shaped foods reported in food consumption surveys be as accurate as possible. This research was conducted to evaluate the accuracy of both a newly developed portion size estimation aid (PSEA) called an adjustable wedge and a traditional PSEA, a 12-inch ruler. Respondents (N = 320) estimated the portion size of different sizes of cakes, pies, and pizzas using both the adjustable wedge and a ruler. For the portions evaluated, average estimation errors for length, width, and area generally were within ± 10%, 20%, and 25%, respectively. Mean errors for area estimations for all portions except one were similar or significantly less (P<0.05) for the adjustable wedge when compared to the ruler. Also, respondents were significantly (P<0.05) more confident in their estimation accuracy using the adjustable wedge. These findings indicate the adjustable wedge may be an effective substitute for the ruler for estimating portion sizes of wedge-shaped foods, and that further refinements of this PSEA may produce even more accurate estimations in dietary surveys.

Last Modified: 10/1/2014
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