As any fan of lightweight, delicate Cocoa Krispies knows (though perhaps I'm generalizing my experience), sometimes it's difficult to judge how much cereal you're really eating. A study from Penn State on flake size, portion control and calorie consumption in breakfast cereals has shown that participants given smaller flakes poured a smaller volume into their bowls but still consumed greater heft and more calories than participants given larger flakes.
From a release:
According to [nutritional sciences professor Barbara Rolls, PhD], national dietary guidelines define recommended amounts of most food groups in terms of measures of volume such as cups.
"This can be a problem because, for most foods, the recommended amounts have not been adjusted for variations in physical properties that affect volume, such as aeration, cooking, and the size and shape of individual pieces." Rolls said. "The food weight and energy required to fill a given volume can vary, and this variation in the energy content of recommended amounts could be a challenge to the maintenance of energy balance."
In the study, 41 adult participants ate cereal for breakfast once a week for four weeks. Some ate the standard-sized wheat flakes, while others consumed the same cereal crushed to 80, 60 or 40 percent of its original volume. All participants poured as much as they wanted from opaque containers of equal-weight amounts of cereal and ate as much as they wanted.
The study authors report that "as flake size was reduced, subjects poured a smaller volume of cereal, but still took a greater amount by weight and energy content." Still, the study notes, "subjects estimated that they had taken a similar number of calories of all versions of the cereal."
Previously: Can dish color influence how much you eat? and Smaller plates may be a tool to curtail childhood obesity
Photo courtesy of Barbara Rolls, Penn State