Would you like air with that?

The size or volume of food is known to affect how much we eat. But what about air?

Researchers at Pennsylvania State University investigated how the air content of a familiar snack food affected the total amounts of energy consumed.

They tested two versions of a cheese puff which contained the same amount of energy by weight (kilojoules per gram) but one was more aerated than the other, so had less energy by volume.

Twenty-eight non-dieting people were served the different snacks on several different occasions. By volume the participants consumed nearly 75% more when served the more aerated snack, but this worked out to be around 300kJ less energy, equivalent to a 21% decrease.

Despite the different energy intakes, there was no difference in participants' ratings of hunger or fullness after consuming the different snacks, and both snacks scored the same for pleasantness of taste.

Source: Appetite, May 2007