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A Comparison of 2 Measurement Aids

Donna M. Matheson, PhD; Kara A. Hanson, RD; Tiffany E. McDonald, MPH; Thomas N. Robinson, MD, MPH

Arch Pediatr Adolesc Med. 2002;156:867-871.

Background  Policy and clinical decisions regarding children's nutrition are often based on dietary intake estimates from self-reports. The accuracy of these estimates depends on memory of both the type of food eaten and the amount consumed. Although children's self-reports of food intake are widely used, there is little research on their ability to estimate food portions.

Objective  To assess the validity of children's estimates of the food portions they consume by means of 2 types of measurement aids: standard 2-dimensional food portion visuals and manipulative props.

Design  Randomized controlled trial.

Participants  Fifty-four African American girls aged 8 to 12 years.

Main Outcome Measures  Girls were served a standard meal and actual intake was assessed by weighing food portions before and after the meal. On completion of the meal, dietitians collected food recalls and portion size estimates from the girls by means of both manipulative props and 2-dimensional food portion visuals, administered in a randomized order.

Results  Absolute value percentage differences between actual and estimated grams of food consumed averaged 58.0% (SD, 102.7%) for manipulative props and 32.8% (SD, 72.8%) for 2-dimensional food portion visuals. Spearman correlations between actual and estimated intakes with both portion size measurement aids were high (range, r = 0.56 to 0.79; all P<.001), with the exception of bread intake (r = 0.16, P = .43). Correlations with actual intakes did not differ significantly between the 2 methods.

Conclusions  Children's self-reported portion size estimates are appropriate for ranking children's relative intakes, but they result in sizable errors in quantitative estimates of food and energy intakes. Caution should be used in interpreting quantitative dietary intake estimates derived from children's self-reports.

From the Stanford Center for Research in Disease Prevention, Department of Medicine (Drs Matheson and Robinson and Mss Hanson and McDonald), and Division of General Pediatrics, Department of Pediatrics (Dr Robinson), Stanford University School of Medicine, Palo Alto, Calif.