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The Clean Plate Club: About 92% of Self-Served Food is Eaten

Wansink, Brian and  Katie Johnson (2014). The clean plate club: about 92 percent of self-served food is eaten. International Journal of Obesity, 39, 371–374. doi: 10.1038/ijo.2014.104.

A significant number of studies in psychology, consumer behavior, and marketing focus on how much food participants serve themselves, rather than how much they actually eat. In this preliminary study, we developed a method of estimating how much food those participants consumed out of the amount they served themselves.

We conducted a systematic review of 14 American and Canadian studies, all with participants over the age of three. Studies reviewed were limited to those with self-served food that was measurable or convertible to grams, and that could be searched in electronic databases (primarily PsychInfo, SSCI, and PubMed). Within these studies, subpopulations were identified based on demographic and food-related factors.

Across all subpopulations, we found that individuals consumed 90.69% of the food they served themselves. Regarding demographics, adults ate 91.7% of what they served themselves, consistently higher than the 59.1% that children ate. Looking at food-related factors, people consumed a higher percentage of self-served healthy foods than unhealthy foods, much more continuous foods (e.g. applesauce) than discrete foods (e.g. carrot sticks), and much more of meals than of snacks. Environmental cues were also influential; people ate a lower percentage of what was on their plate while distracted. They also consumed a higher percentage when eating from smaller plates and bowls.

We concluded that adults tend to consume almost all of the food they serve themselves. These preliminary findings could serve as a predictor for the amount of food actually eaten in self-serve studies. Further, our findings can be applied to different subgroups in these studies, according to the population(s) being observed.