Q: Do aerated beverages, like milk shakes that contain lots of air, make you feel fuller and thus help control appetite?
A: Maybe, at least a little. Aerating a drink by whipping it into a foam increases its volume. So it’s not surprising that studies have found that highly aerated beverages (and sometimes foods containing lots of air, such as popcorn or puffed cereal) increase the feeling of fullness (satiety). Most aerated beverages lose their bubbles fairly quickly, before or after you consume them, so the researchers have often used special ingredients (such as xanthan gum) and powerful blenders to produce more stable foam.
In a study published in the American Journal of Clinical Nutrition in February 2015, researchers compared aerated and non-aerated versions of a nonfat-milk beverage in men who drank the beverage after an overnight fast; aeration more than tripled the volume of the milk. The aerated drink greatly increased stomach volume and slowed stomach emptying (as seen on MRI scans over four hours) and reduced hunger (based on an appetite questionnaire) compared to the non-aerated beverage, which had the same number of calories.
As the researchers noted, increased distention may trigger receptors in the stomach wall to signal the brain to reduce appetite. There may be a psychological effect as well: People tend to feel more satiated when they perceive that they’re consuming a larger volume of food or fluid.
This is in line with the weight-control concepts proposed by Barbara Rolls, PhD, in her well-regarded Volumetrics eating plan, which emphasizes foods with low calorie density, usually thanks to their high water or air content. She tested aeration back in 2000 in a study also in the American Journal of Clinical Nutrition. Before eating lunch, participants drank high-calorie shakes (containing yogurt, whole milk, and cream) that had varying degrees of aeration; all shakes weighed the same and had the same number of calories. After drinking the most highly aerated shakes, peoplereported the greatest reduction in hunger—and they subsequently consumed 12 percent fewer calories at lunch than when they drank the non-aerated shake (half the volume).
If you want to try aerated beverages, keep in mind that many factors affect satiety and appetite, and what happens in a lab setting may not happen in the real world. In particular, the beverages' satiety effect would be altered by other foods in your stomach and by ingredients in the beverage itself. Simply adding water (especially if carbonated) to a beverage or meal may have at least as big an effect on satiety as added air does. Moreover, shakes made in home blenders typically deflate fairly quickly, which would minimize or eliminate any such effect. Another wrinkle: Whipped-up high-fat beverages tend to stay aerated longer than nonfat fluids, but high-calorie milk shakes and whipped cream, however aerated they are, will not promote weight control.
Finally, if aerated drinks distend your stomach enough to increase satiety, the bloating may make you uncomfortable.