Food portion estimation by children with obesity: the effects of estimation method and food type

Several factors influence children's ability to report accurate information about their dietary intake. To date, one understudied area of dietary assessment research relates to children's ability to estimate portion sizes of food. The purpose of this cross-sectional research was to examine food portion size estimation accuracy in 7- to 18-year-old children with obesity. Two within-subject experiments (Experiment 1: n=28, Experiment 2: n=27) were conducted in Edmonton, Alberta, Canada, during 2007-2008. Three types of portion size measurement aids (PSMAs) (eg, measuring cups and spoons, household objects [full and half-sized], and modeling clay) were counterbalanced in a Latin Square design for participants to estimate four types of foods (ie, solid, liquid, amorphous pieces, and amorphous masses). Analyses of variance conducted on percent of signed and absolute errors yielded significant PSMA type×food type interactions (P<0.01) in both experiments. Across all food types, for Experiments 1 and 2, measuring cups and spoons produced the least accurate estimates with respect to absolute error (54.2% and 53.1%, respectively), whereas modeling clay produced the most accurate estimates (40.6% and 33.2%, respectively). Half sizes of household objects also yielded enhanced accuracy (47.9% to 37.2%). Finally, there were significant differences in accuracy between amorphous pieces (eg, grapes) vs amorphous masses (eg, mashed potatoes; P<0.01), indicating that there are qualitative differences in how different amorphous foods are estimated. These data are relevant when collecting food intake data from children with obesity and indicate that different PSMAs may be needed to optimize food portion size estimation accuracy for different food types.