According to a new study by researchers at Oxford University, fatty foods are more addictive than their lighter counterparts. This is not just due to the taste, but also because of the mouthfeel. The high-fat products increase the viscosity of liquid food, which reduces friction as it slides against the tongue and walls of the mouth. To test this theory, the researchers prepared vanilla-flavored milkshakes with varying fat and sugar content. They also procured pig tongues from a local butcher and measured the sliding friction of their milkshakes in conditions reminiscent of the human mouth.

The results showed that milkshakes with higher fat content had lower friction levels. When asked how much they were willing to pay for more milkshakes, participants showed a preference for shakes with higher fat content. The researchers used functional magnetic resonance imaging (fMRI) to observe changes in brain activity while participants tasted the different shakes. The study found that differences in composition and pleasantness were reflected in reactions in the orbitofrontal cortex, which is responsible for sensations and attractiveness of food.

Further research was conducted on curries with different fat content to confirm that mouthfeel plays a significant role in food choices. Participants were asked to choose their favorite lunch from three different curries without knowing that they were being observed by researchers. Results showed that those whose orbitofrontal cortex reacted strongly to greasy mouthfeel during shake testing piled their plates high with fatty meals at lunchtime.

The findings of this study could have implications for developing low-calorie foods that still have an addictive quality to them, without sacrificing taste or texture. The study was published in The Journal of Neuroscience.