Portion-size estimation training in second- and third-grade American Indian children

Training in portion-size estimation is known to improve the accuracy of dietary self-reporting in adults, but there is no comparable evidence for children. To obtain this information, we studied 110 second- and third-grade American Indian schoolchildren (34 control subjects were not trained), testing the hypotheses that a 45-min portion-size estimation training session would reduce children's food quantity estimation error, and that the improvement would be dependent on food type, measurement type, or both. Training was a hands-on, 4-step estimation and measurement skill-building process. Mixed linear models (using logarithmic-transformed data) were used to evaluate within- and between-group differences from pre- to posttest. Test scores were calculated as percentage estimation errors by difference and absolute value methods. Mean within-group estimation error decreased significantly (P < 0.05) from pre- to posttest for 7 of 12 foods (trained group) by both calculation methods, plus 3 additional foods by the difference method and one additional food by the absolute value method. Significant (P < 0.05) between-group differences occurred for 3 foods, reflecting a greater decrease in estimation error for the trained group. Improvement was greatest for solid foods estimated by dimensions (P > 0.05) or in cups (P < 0.05), for liquids estimated by volume or by label reading (P < 0.001), and for one amorphous food estimated in cups (P < 0.01). Despite these significant improvements in estimation ability, the error for several foods remained > 100% of the true quantity, indicating that more than one training session would be necessary to further increase dietary reporting accuracy.