Effect of Gradually Reduced Portion Size Estimation Training on Portion Size and Daily Energy Intake Estimation Accuracy

OBJECTIVES: We examined the effect of gradually reduced guidance and feedback on portion size and daily reported energy intake (EI) estimation accuracy. We hypothesized that training would result in relatively accurate portion size estimation at a group level and that portion sizes would be most accurately estimated for solid foods compared with amorphous and liquid foods. We also expected that those who performed better in portion size testing to more accurately report EI. METHODS: In a single session, healthy, nonsmoking participants (n = 29; 38% F; aged 23.0 ± 4.8 y; BMI 22.7 ± 3.2 kg/m(2) (mean ± SD)) were given training and gradually reduced written and oral guidance for portion size estimation over three training meals (meals 1–3) followed by one test meal. No instruction was provided for the test meal (meal 4), but oral feedback was provided afterwards. The meals used typical American foods and consisted of food replicas supplemented with real condiments and beverages. The next day, participants were invited to eat breakfast, lunch, and dinner at the university food court. Food selection was unrestricted and all foods and beverages chosen by participants were weighed by researchers who completed a weighed food intake record. After consuming each meal, participants recorded their food intake from the food court using a web-based food diary (ASA24 in record mode). EI from the food diary was calculated and compared with EI from the weighed food record. RESULTS: Repeated measures ANOVA showed that portion size estimation tended to worsen with meal progression, with meals 4 and 2 being significantly underestimated by −4.5 ± 31.2 and −38.9 ± 120.5 g, respectively, versus 17.4 ± 18.0 g overestimation in meal 1 (p < 0.05). The percentage of foods correctly estimated was higher with solids (83.7%) and liquids (87.1%) compared with amorphous foods (75.3%). Correlations between portion size estimation accuracy and daily EI estimation accuracy were not significant (r = 0.18; p = 0.37). CONCLUSIONS: These results suggest that gradually reduced guidance may not be useful for portion size estimation. Alternatively, participants may not have been familiar with the foods used in the test and training meals, or practice on a greater number of meals containing a broader array of foods may be needed. FUNDING SOURCES: NIDDK.