It’s not just the taste that makes people prefer fleshy fat yogurt or ice cream over a lighter alternative, but also the mouthfeel. According to research conducted by Fabian Grabenhorst and his team at Oxford University, the brain area responsible for sensations and food attractiveness, known as the orbitofrontal cortex, is particularly excited by the recognition of fatty foods.

The researchers found that fat increases the viscosity of liquid food, which reduces friction as it slides against the tongue and walls of the mouth. To investigate this further, they prepared vanilla-flavored milkshakes with varying fat and sugar content, including an option with a thickener used in the food industry to give juiciness. They also procured pig tongues from a local butcher to measure the sliding friction of their milkshakes under conditions similar to those in the human mouth.

The results showed that friction decreased according to the fat content of the shake. The study then involved more than 20 test subjects who were asked to rate how much they were willing to pay for more milkshakes after tasting them. Their brain activity was also imaged using functional magnetic resonance imaging (fMRI) during this process. The researchers found that differences in shake composition and pleasantness were reflected in reactions of the orbitofrontal cortex.

Grabenhorst explained that their findings could help develop low-calorie foods that still provide a satisfying mouthfeel experience for consumers. The study was published in The Journal of Neuroscience.