Determining proper portion size is important for weight management. Serving sizes impact how much food someone chooses to eat (Haynes et al, 2019), but Americans tend to have erroneous estimates of serving sizes (Faulkner et al., 2012). This study used products with Front of Package (FOP) labels (a 1-4 star healthfulness rating) to test how a food type and a public service announcement (PSA) explaining the labels impacted serving size estimations.
172 parent-child dyads (93% female, M age= 38.40, 87% white) were randomly assigned to either see a PSA (n = 59) or not (n =113) before estimating serving sizes for 2 cereals (wheat/barley and rice cereal) and 2 snack foods (potato chips and pretzels). It was predicted that participants who viewed the PSA would underestimate portions of less healthful foods (chips, pretzels), relative to foods with more stars (the cereals).
Regressions show food type is a significant factor, predicting 91% of the variance in serving size estimation (R2 =.910, F (3, 684)= 2294, p<.001). Individuals overestimated serving sizes for the dense wheat/barley cereal (M= 5.8% over) and pretzels (M= 12.8% over), but underestimated the rice cereal (M= 26% under) and potato chips (M= 9.1% under). Analyses showed the PSA did not predict serving size estimations (all R2 <.01, Fs (1, 170) ranged 0.245 – 1.66, ps>.05).
Findings suggest watching a PSA did not significantly impact serving size estimations, but food type was associated with serving size over/underestimation. It is likely that product density (reflected in the cereal comparison) and health halo reputation (reflected in the snack food comparison) played a role in the divergent estimations. Overestimation of serving sizes may be implicated in over-consumption of certain food types (e.g., snacks perceived as healthier, such as pretzels). By identifying factors related to errors in serving size estimation, researchers can highlight potential biases for those attempting to regulate portions.