Next time you are snacking on a handful of nuts, be sure to portion them out: According to new research published in the Journal of Consumer Research, people perceive foods that are either hard or have a rough texture to have fewer calories.
In one study, participants were asked to evaluate several television commercials and were provided hard or soft bite-size brownies to enjoy while watching. Participants who were also asked to think about calories consumed more of the hard treats than the soft ones, but those who didn't pay attention to calories consumed more of the soft snacks. The researchers believe this is due to "oral haptics–calorie estimation," which is the relationship between how much you chew a food and how you perceive the calories. The more you chew, the fewer calories you believe a food has.
I think as a general rule most people would agree that raw veggies, i.e. a hard food, are low in calories. But maybe the reason you find it difficult to put down your fork (or spoon) down when eating mashed potatoes or ice cream isn’t only the taste that does it, but also the texture.
Interesting, but not all soft foods are high in calories. For example, oatmeal and yogurt are excellent meal choices. Similarly, not all hard foods are low in calories—pretzels, rock candy, and licorice all come to mind for me. As a general rule, though, I do find that people eat slower when consuming hard foods, which could lead to less consumption and fewer calories by default.
Really, I think this area of research needs to be further explored. As the study authors conclude, "Understanding how the texture of food can influence calorie perceptions, food choice, and consumption amount can help nudge consumers towards making healthier choices."