In the eye of the beholder--the effect of plate and bowl size on children's self-served portion sizes

Background: Large food portions are thought to contribute to child obesity by inflating consumption norms and stimulating intake. These effects are attributed to visual cues; including the size of eating implements [EI] (i.e. plate, bowls). Whether EI influences children's self-selected portion [SSP], however, is not well established. Objectives: To evaluate the effect of EI on SSP in children. We hypothesized children's SSPs would be greater when serving with larger EI. Methods: Participants were 42 1st grade children, observed weekly during lunch offered as part of the USDA National School Lunch Program. A within subjects design was used where children served themselves using reference or large EI (~100% increase surface area/volume); condition order was counter balanced across classrooms. An amorphous (i.e. pasta) and unit food (i.e. chicken nugget) entrée were evaluated on separate days. Applesauce and mixed vegetable side dishes were evaluated at each meal. Fixed portions of milk and bread were provided. SSP of entrée and side dishes were primary outcomes. BMI-for-age z-scores were calculated for inclusion in final models, with child gender, food preferences, and demographics as covariates. Results: Main effects of EI size on SSP were significant for the amorphous entrée (p<0.01), unit entrée (p<0.05), fruit (p<0.0001), and vegetable (p<0.01). Children served themselves approximately 22.5% more amorphous entrée (77 kcal), 11.6% more unit entrée (49 kcal), 12.0% more fruit (18 kcal), and 11.0% more vegetable (9 kcal) when using larger EI. Conclusion: These findings provide evidence that size-related visual cues influence young children's self-served portions at meals.