A recent study by Oxford University brain researcher Fabian Grabenhorst and his colleagues has shed light on why many people prefer high-fat meat-based yogurts or ice cream over lighter alternatives. According to the researchers, fat increases the viscosity of liquid food, which reduces friction as it slides against the tongue and walls of the mouth. This mouthfeel makes high-fat products addictive.
To test their hypothesis, Grabenhorst and his team prepared vanilla flavored milkshakes with different fat and sugar content. They also obtained pig tongues from a local butcher to measure the sliding friction of their milkshakes under conditions that resemble the human mouth. The results showed that friction decreased in line with the fat content of the shake.
The researchers then recruited more than twenty subjects who were asked to taste and rate how much they were willing to pay for each milkshake. Brain activity was recorded using a functional magnetic resonance imaging device (fMRI) while the subjects tasted the milkshakes. The findings revealed that differences in composition and pleasantness were reflected in responses from the orbitofrontal cortex, a part of the brain associated with sensory pleasure and reward processing.
Grabenhorst said that these findings could help develop low-calorie foods that still have a satisfying mouthfeel. He also noted that understanding how fat affects our brains could lead to new approaches for treating obesity and related disorders such as diabetes and heart disease.