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Previous research has established that environmental cues and portion size have a greater impact on consumption than BMI or body composition. For adults, the larger the serving vessel, the more food gets consumed, in part because of the size-contrast illusion and the DelBoeuf illusion. Childhood obesity is a growing concern and the amount of food a child eats is related to how much a caregiver serves the children, particularly younger children who do not have the motor skills to serve themselves. We hypothesize that children, like adults, will request more food when they have a large bowl and will consequently eat more food too.
We conducted two studies to test whether bowl size impacts how much cereal children request and consume. In the first study, 81 preschoolers were divided into two groups, children in one group were given an 8-oz. bowl and children in the other group were given a 16-oz. bowl. Children in each group were initially served 3-4 grams of pre-sweetened cereal and milk, similar to the kinds of foods typically served at home. The researchers asked if the children would like more, and if the child did, then they poured an additional 3-4 grams, a cycle which continued as long as the child still wanted more cereal. According to protocol, the children did not eat the cereal, as it posed a choking hazard. Instead, they were given a toy after participation in the study. The height and weight of each child were taken to calculate BMI, which was then adjusted to a percentile score outlined by the CDC. An independent sample t-test was conducted using bowl size as a predictor of the amount of cereal requested.
The results of this initial study showed that when children were served in the larger bowl, they requested 87% more cereal than children who were served in the smaller bowl. No correlation existed between factors such as BMI, gender, and age. The average fill-level of the small bowl was 32% and the largest amount of cereal requested to fill the bowl was 61%, indicating no ceiling effect with the smaller bowl. The study indicates that preschool children are influenced by the size of the bowl and will request more cereal in a larger bowl.
The second study involved 18 children between 6-10 years old attending a summer camp. On the first test day, the campers were randomly provided a small 8 oz. or large 16 oz. bowl and where then asked how much cereal and milk they wanted. On the second test day, the campers where provided with the alternate bowl size, children who received a small bowl on the first day were given a large bowl on the second day and vice versa. Hidden scales and remote sensors were used to determine how much cereal and how much milk each child was served. Food consumption was measured by subtracting the amount of cereal and milk that remained at the end of breakfast. On the last day of camp, the students were presented with 24 cereal bowls of different sizes and shapes and asked to choose the one that was most similar to the bowls that they used at home.
In this study, children requested 69% more cereal and milk when given the larger bowls. In addition, there was a 42% increase in consumption after subtracting plate waste (257.7 vs. 181.7g). Upon closer examination, larger bowls increased food waste (92.2 vs. 25.4g). The average size of the bowl selected by the students was 19.2 ounces, and 14 of the 18 children said that this was the same size bowl they used at home.
These two studies show that bowl size is a great indicator of child cereal consumption despite BMI, age, and gender. Since 78% of the children indicated eating out of the same sized bowl as their parents, one means of curbing overconsumption among children is to use smaller bowls.
Wansink, Brian, Koert van Ittersum, and Collin R. Payne (2013). Larger bowl size increases the amount of cereal children request, consume, and waste. Journal of Pediatrics, 164 (2), 323-326. doi: 10.1016/j.jpeds.2013.09.036.