The Portion Size Effect: A Review

Obesity rates have been growing exponentially over the past two decades in North America warranting a label of epidemic, and many fingers have been pointed at the food industry for its alarming increases in portion sizes. Generally speaking, the portion-size effect describes the principle that participants ingest more calories when a larger portion size is served to them. The portion-size effect is well established in the literature. This paper summarizes current knowledge in the field of eating psychology regarding the portion-size effect. The portion-size effect has been empirically demonstrated in a diversity of participants and situations. These demonstrations have led to the development of theories regarding the mechanisms by which portion sizes affect energy intake. An important controversy in the literature concerns the empirical evidence (or lack thereof) for weight differences in terms of response to portion-size manipulations. This controversy has direct effects on the credibility of the hypothesis that the portion-size effect contributes to the obesity epidemic. Finally, the portion size literature discusses possible applications of the portion-size effect in the real world. These potential applications are thought to have links to obesity control.