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The size of food packaging and portions has steadily increased over the past 30 years, as have portion sizes and consumption rates. This study examined whether visual cues related to portion size can influence intake volume without altering either estimated intake or satiation. We predicted that individuals would consume more ounces and calories when such a cue was unknowingly altered, thus suggesting that individuals may sometimes rely on a visual point–of–reference for cessation.
We conducted a soup study on 54 participants at a Midwestern university. The participants were served their soup. Half of the participants were served soup in a normal bowl, which provided an accurate visual cue, food portion, and half were served soup in a self–refilling bowl, which provided a biased visual cue. The self–refilling bowls slowly and imperceptibly refilled as their contents were consumed. We measured the participants' soup intake volume, their intake estimation, their self–perceived consumption monitoring, and satiety.
We found that the participants who were unknowingly eating from self–refilling bowls ate 73% more soup that those eating from normal bowls. However, the participants eating from soup–refilling did not believe they consumed more nor did they perceive themselves as more sated than those eating from normal bowls. This effect remained regardless of BMI. We conclude that the amount of food on a plate or in a bowl provides a visual cue or consumption norm that can influence how much one expects to consume and how much one eventually consumes. When there was an accurate visual cue as to how much one had eaten, people stopped eating at an earlier point than when there was a biased visual cue of what they had eaten. Since people use their eyes to count calories and not their stomachs, the use of smaller bowls is an important tool for guiding consumption habits. Understanding the importance of having salient, accurate visual cues can play an important role in the prevention of unintentional overeating.
Wansink, Brian, James E. Painter, and Jill North (2005). Bottomless Bowls: Why Visual Cues of Portion Size May Influence Intake. Obesity Research, 13(1), 93–100. doi: 10.1038/oby.2005.12 --