The smaller the cereal flakes, the more you tend to eat

Researchers have shown that when cereal flakes are reduced by crushing, people pour a smaller volume of cereal into their bowls, but still take a greater amount by weight and calories.

Barbara Rolls, professor of nutritional sciences and Helen A. Guthrie Chair in Nutrition, said that people have a really hard time judging appropriate portions.

According to Rolls, national dietary guidelines define recommended amounts of most food groups in terms of measures of volume such as cups.

The researchers tested the influence of food volume on calorie intake by systematically reducing the flake size of a breakfast cereal with a rolling pin so that the cereal was more compact and the same weight filled a smaller volume. In a crossover design, the team recruited 41 adults to eat cereal for breakfast once a week for four weeks.

The cereal was either standard wheat flakes or the same cereal crushed to reduce the volume to 80 percent, 60 percent or 40 percent of the standard. The researchers provided a constant weight of cereal in an opaque container and participants poured the amount they wanted into a bowl, added fat-free milk and non-calorie sweetener as desired and consumed as much as they wanted.

The research showed that as flake size was reduced, subjects poured a smaller volume of cereal, but still took a significantly greater amount by weight and energy content.

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.

The study has been published in the Journal of the Academy of Nutrition and Dietetics.