consumed on the average 15 oz (443 ml), that is 73% more with some people
consuming nearly a liter of soup in 20 min. All participants reported the same range
of fullness regardless of the amount they consumed. People relied on visual cues,
eating about half a bowl, and not internal cues that are the physiological biomarkers
of satiety or feelings of fullness and satiation or a lack of desire to eat. These visual
cues provide consumption norms that people may or may not be consciously
monitoring when they are eating (Wansink2004b,c; Wansink et al. 2007 ). Using
chicken wings as the test food, Wansink and Payne ( 2007 ) demonstrated that when
the pile of bones was left on the table as a visual reminder of what had been
consumed, people ate an average of 2 fewer wings (28% less) than people at tables
that had the bones periodically removed.
People also misjudged their caloric intake. People with regular soup bowls and
those with the refilling bowls reported similar intakes averaging 127 calories, but real
intakes averaged 155 and 268 calories, respectively. Repeated studies have shown that
the larger the quantity consumed, the greater the disparity between reported intake by
size and caloric density. Larger portions lead to greater underestimations of intake,
with people generally underestimating consumption by 20–40% (Chandon and
Wansink 2007 ; Wansink and Chandon 2006 ). Obese individuals have greater
underreporting of consumption butunderestimateabout the same amount as normal
weight individuals. The number of underestimated calories is greater because they
consume larger portion sizes (Archer et al. 2013 ; Wansink and Chandon 2006 ).
Barbara Rolls and colleagues have conducted a number of experiments assessing
the impact of portion size versus caloric density on satiety or perceived fullness
following a preload of solid or liquid foods (Flood et al. 2006 ; Kral and Rolls
2004 ). They found that college-age students reported equivalent size portions
(volumes) to be as or morefilling than portions that contained twice the calories: for
example, a 1/4-lb hamburger that was volumized with lettuce and tomatoes was as
filling as a½-pound hamburger, and a½glass smoothie or milk shake volumized
with air to a full glass size was asfilling as a full glass (Kral and Rolls 2004 ; Rolls
et al. 2000 ). In one experiment, doubling the volume of a liquid test meal increased
the rating of sensory-specific satiety and decreased pleasantness; however, doubling
the caloric content did not change ratings for either dimension (Bell et al. 2003 ).
These studies corroborated the work of Wansink and colleagues: larger portions
resulted in increased intakes regardless of caloric density. The conclusion is that
volume trumps calories and people believe what they see rather than relying on the
physiological impact, actual amount consumed, or energy density of what they eat
(Ello-Martin et al. 2005 ; Wansink 2010 ). Air and water can increase volume
without increasing calories and is a suggested strategy for controlling weight (Rolls
and Barnett 2000 ). However, this may be only a short-term effect as gut-brain
satiety mechanisms detecting a deficit in macronutrients and calories exert physi-
ological mechanisms to initiate eating and reinstate homeostasis (Guyenet and
Schwartz 2012 ).
Furthermore, people whothinkthey eat more report greater positive affect than
those whothinkthey consume skimpier portions (Rolls 2014 ; Wansink 2010 ). In a
series of experiments and observations, Wansink and colleagues have noted that a
202 L.S. Lieberman