Public Release: 

Foods puffed up with air can aid weight management

Penn State

University Park, Pa. -- You can't live on air, but Penn State researchers have shown that big, puffed-up food servings can satisfy better than small, packed-down, calorie-equivalent portions - a fact that can help you feel full on fewer calories.

Study director Dr. Barbara Rolls, who holds the Guthrie Chair in Nutrition in Penn State's College of Health and Human Development, says, "We're not suggesting you try to fill up on lots of airy foods. You might get a stomachache and would probably burp a lot! But this study does show that you can trick your senses into believing you have eaten more food by pumping up the size of the portion with air."

The study is detailed in the current issue of the American Journal of Clinical Nutrition in a paper, "Increasing the Volume of a Food by Incorporating Air Affects Satiety in Men." The authors are Rolls, Elizabeth Bell, doctoral candidate in nutrition, and Bethany W. Waugh, manager, Laboratory for the Study of Human Ingestive Behavior.

The 28 lean men who participated in the study ate breakfast, lunch and dinner one day a week in the laboratory for four weeks. Thirty minutes before lunch, they were served one of three strawberry smoothies. The researchers made the smoothies with exactly the same ingredients but mixed them for different amounts of time in a blender. The smoothies filled either half, three-quarters or a full glass. The bigger the smoothie the men consumed, the less they ate at lunch. After consuming the biggest smoothie, the men ate 12 percent - or about 100 calories -less lunch than they did when they drank the smallest one - even though both drinks contained the exact same ingredients and the same number of calories.

In her best selling book "Volumetrics," written with Robert Barnett, Rolls explains that the research points to a way to decrease the daily amount of calories you consume while still feeling full and satisfied. Whipped foods, she notes, can be especially useful. "You see a bigger portion, and you get more sensory stimulation as you consume it," the authors write.

"Try whipped foods in moderation such as low-fat frozen desserts. Get creative with blender drinks. Choose air-popped popcorn; its energy density is not low, but it takes three cups to give you 90 calories (try it without butter - add low-fat seasoning instead.) Foods with irregular shapes also produce a bigger volume in a given portion because they don't pack down. Think of flaky or puffed cereals. In other words: Think big," they add.

"Volumetrics" is full of other suggestions, based on Rolls's research, for decreasing calorie intake while remaining full and satisfied. The Penn State researcher explains that her group's research has shown that feeling full depends on eating a satisfying amount of food. Tiny portions just don't do it. The energy density of food, or the ratio of calories to the weight of food, is what matters. Foods with a high energy density have lots of calories in a small serving and are typically lower in water or air content. For example, a 100-calorie serving of raisins, a high-energy density food, contains only one-quarter cup. A 100 calorie serving of grapes, a low-energy density, high-water content food, contains one and two thirds cups.

"Volumetrics," published by Harper Collins, provides more information on the energy density of specific foods. The book also details Rolls' energy density eating plan and offers menus, recipes and tips for modifying your favorite dishes.


EDITORS: Dr. Rolls is at (814) 863-8482 or at by email.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.