Just Add Air?

One of the principles of volumetrics, developed by Dr. Barbara Rolls of Pennsylvania State University, is that just adding air (by blending foods) can make you feel fuller. If this theory sounds full of hot air, check out these facts.

In a recent study, Rolls and research associates presented subjects with smoothies, monitored their eating habits, and asked them to self-report on satiation levels. One group’s smoothies were blended for twice as long as the other group’s smoothies. This extra blending time allowed more air bubbles to form and increased the volume of the smoothie, thereby making it appear to be and actually be larger, even though no extra calories were added. The blended-longer group reported feeling full for longer and ate 12% less than the other group.

There are several possibilities as to why one variable – the extra air – impacted people’s satisfaction and eating habits. One potential explanation is that the smoothie appeared a bit larger (though the difference would have been very slight) and people felt fuller longer, so they did not eat as much. The second theory, which Rolls supports, is that a higher volume of food is more satisfying than a lower volume of food with the same caloric content.

No matter the reason, the facts remain: people who were served higher volumes felt more full and ate less. Even more exciting is that this approach also works with another famous zero-calorie substance: water! The same effects have also been found with low-calorie foods like lettuce and celery. So next time you have a smoothie, ask for extra blend time!