experimental studies (including some of Wansink’s studies) found only a marginal
effect of dishware size on food intake (Robinson et al. 2014 ). The standardized
mean difference (SMD) in food intake between smaller and larger dishware was
only−0.18, with a high degree of heterogeneityI^2 = 77%. Some participants with
larger plates took large portion sizes but did not consume all the food while others
with small plates took multiple servings. Studies included the following:
within-subject/repeated measures and between-subject/independent group designs;
laboratory andfield settings; experimenter provided or self-served portions; main
meals and snack foods; and plates and bowls. Subjects included male and female
adults and children with a range of BMIs. Overall effects were larger for studies in
naturalistic settings (SMD =−0.47) than those using bowls (SMD =−0.67). Since
there have been no long-term studies assessing the effect of plate size on portions or
caloric intake, and the results of short-term studies show mixed results, Robinson
et al. ( 2014 ) conclude that the efficacy of the use of smaller dishware as a weight
loss strategy has not been demonstrated. A recent study corroborating the
meta-analysis found that adults using large plates at a lunch buffet served them-
selves more vegetables than those with smaller plates, resulting in no significant
effect of plate size on total energy intake (Libotte et al. 2014 ).
Findings from Wansink’s soup, ice cream, and Chinese buffet studies and also
from Rolls’studies primarily of college students suggest that people may have
visual consumption norms based on visual plate or soup bowlfill-levels that
determine the amount served and consumed. One hypothesized explanation is the
Delboeuf illusion in which the color contrast of the food compared to the dinner-
ware sets a false perception of the size of the portion on the plate. Franz Joseph
Delboeuf (Burnham 2012 ) found that the perceived difference in the size of two
identical circles when one of the circles was surrounded by a much larger circle was
smaller than when it was surrounded by only a slightly larger circle, as shown in
Fig.10.2. Wansink and colleagues tested this by serving pasta with red or white
sauce on red or white plates. They found that reducing the color contrast between
dinnerware and the background tablecloth, or increasing the color contrast between
Fig. 10.2 Delbeouf and horizontal–vertical optical illusions (Burnham 2012 )
204 L.S. Lieberman