Variations in cereal volume affect the amount selected and eaten for breakfast

Abstract

Food volume could influence both the portions that people take and the amount that they eat, but these effects have had little investigation. The influence of food volume was tested by systematically reducing the flake size of a breakfast cereal so that the cereal was more compact and the same weight filled a smaller volume. In a crossover design, 41 adults ate cereal for breakfast once a week for 4 weeks during 2011 and 2012. The cereal was either standard wheat flakes or the same cereal crushed to reduce the volume to 80%, 60%, or 40% of the standard. A constant weight of cereal was provided in an opaque container and participants poured the amount they wanted into a bowl, added fat-free milk and noncalorie sweetener as desired, and consumed as much as they wanted. Results from a mixed linear model showed that as flake size was reduced, subjects poured a smaller volume of cereal, but still took a greater amount by weight and energy content (both P values <0.0001). Despite these differences, subjects estimated that they had taken a similar number of calories of all versions of the cereal. They ate most of the cereal they took, so as flake size was reduced, breakfast energy intake increased from a mean±standard error of the mean of 286±18 kcal to 358±19 kcal, an increase of a mean±standard error of the mean 34%±7% (P<0.0001). These findings demonstrate that variations in food volume associated with the size of a food's individual pieces affect the portion served, which in turn affects energy intake.

Keywords: Adults; Breakfast cereal; Energy intake; Food volume; Portion size.

Figure 1

(A) These beakers illustrate the reduction in the flake size and volume of breakfast cereal served in a crossover study of 41 adults. The same weight of the commercially available cereal (100%) was crushed using a uniform procedure to reduce the volume to 80%, 60%, and 40%. In the study, participants poured the cereal from opaque containers and could not see the cereal until it was in the bowl. (B) This graph shows the energy content of the cereal that subjects poured compared with their estimates of the number of calories in the cereal they poured (mean ± standard error of the mean). For cereal energy, means with different letters are significantly different (P< 0.04); for estimated cereal energy, there were no significant differences between means. Thus, as cereal flake size and volume decreased, subjects took more calories, but their estimates of the calories taken did not change. Estimates marked with an asterisk are significantly different from the actual energy content of the cereal with the same flake size (P< 0.04).

Figure 2

This graph shows breakfast energy intake (mean ±SEM) of 41 adults in a crossover study that tested the effects of reducing the flake size and volume of cereal. For cereal intake and for breakfast intake, means with different letters are significantly different (P<0.02); for milk intake, there were no significant differences between means (P>0.08). Breakfast intake also included a small amount of energy from hot beverages, which did not differ across meals (mean 6±1 kcal; P=0.39).