Recent research published in the Journal of Neuroscience reveals a fascinating link between the texture of fatty foods and the brain’s reward system. The study found that the smooth texture of high-fat liquid foods activates a specific area in the brain called the orbitofrontal cortex, which is involved in assigning economic value to sensory experiences. This discovery could pave the way for designing healthier low-calorie foods that still satisfy our cravings for rich, fatty textures.
The motivation behind the new study stemmed from a growing need to understand why humans have a strong preference for high-fat foods. Previous research has established that foods rich in fat and sugar tend to elicit a pleasurable mouthfeel, which can drive eating behavior and contribute to obesity.
By investigating the neural mechanisms behind this preference, the researchers aimed to uncover how the brain translates the physical properties of food into subjective valuations that influence eating habits. This understanding could help develop low-calorie foods that mimic the rewarding texture of high-fat foods, potentially aiding in the fight against obesity.
The study involved 22 healthy volunteers aged 19 to 36, who participated in a series of experiments designed to isolate and examine their responses to different textures and flavors of liquid foods. The participants were asked to sample various high-fat and low-fat milkshakes with controlled sugar content, while their brain activity was monitored using functional magnetic resonance imaging (fMRI). The milkshakes were designed to vary in texture by altering their viscosity (thickness) and coefficient of sliding friction (CSF), which measures how smoothly the liquid moves in the mouth.
Participants were trained to move their tongues in a standardized way while sampling the milkshakes to ensure consistent distribution and sensory stimulation. They rated the sensations of sweetness, thickness, and oiliness of each sample and placed monetary bids indicating how much they would pay to consume more of each milkshake. This allowed the researchers to link sensory perceptions with economic valuations and neural activity.
The study found that the orbitofrontal cortex (OFC) was particularly sensitive to the smooth texture of high-fat foods. When participants sampled milkshakes with lower sliding friction (smoother texture), this brain area showed increased activity. Moreover, the OFC activity patterns not only reflected the physical texture but also correlated with the participants’ economic valuations (willingness to pay) for the foods.
Interestingly, while viscosity also influenced texture perceptions, it was the CSF that had a stronger impact on the ratings of thickness and oiliness, as well as on the economic valuations. Foods with lower CSF were generally rated higher for oiliness and thickness, and participants were willing to pay more for these smooth-textured, high-fat foods.
Additionally, the study showed that the sensitivity of the OFC to these textures predicted participants’ preferences for high-fat foods in a separate naturalistic eating test. This suggests that the OFC plays a key role in how we perceive and value the smooth textures of fatty foods, linking sensory input to economic decisions.
The study provides valuable insights into the neural mechanisms underlying food texture valuation. But it has some limitations. The sample size was relatively small, and the study focused on a specific age and health demographic, which may not be representative of the broader population. Future research could include a more diverse group of participants to see if these findings hold across different ages, health conditions, and cultural backgrounds.
Additionally, the study focused on liquid foods. Solid foods have more complex textures and may interact differently with the oral surfaces, potentially leading to different neural and economic responses. Further research could explore how various textures of solid foods influence brain activity and eating behavior.
Another area for future research is the investigation of how these findings can be applied to develop healthier food options. By understanding how the brain values food textures, food scientists can design low-calorie fat replacements that mimic the desirable textures of high-fat foods, potentially helping to curb overeating and obesity.
“Here we showed that the frictional properties of liquid foods influence not only subjective perceptions but also economic valuations measured in incentive-compatible auctions, naturalistic eating behavior, and neural reward responses,” the researchers wrote. “Our approach using biologically plausible tribology tools to quantify food textures and relate them to human perceptions, economic valuations, and neural measures could help validate the design of foods that have both healthy nutrient compositions and attractive oral-texture properties.”
“In conclusion, our findings show that the human OFC responded to foods in the mouth by encoding the CSF, a physical oral-texture parameter that mediated the influence of fat content on subjects’ economic food valuations. Activity patterns in OFC combined sliding-friction signals with representations of subjective oiliness and economic value and explained fat preferences during naturalistic eating. Future studies could investigate how the presently identified neural mechanism for linking oral-textural properties of high-fat foods to eating behavior could contribute to overeating and obesity.”
The study, “A Neural Mechanism in the Human Orbitofrontal Cortex for Preferring High-Fat Foods Based on Oral Texture,” was authored by Putu A. Khorisantono, Fei-Yang Huang (黃飛揚), Michael P. F. Sutcliffe, Paul C. Fletcher, I. Sadaf Farooqi, and Fabian Grabenhorst.
