Obesity: It’s All in Your Head

Tang, D. W., Fellows, L. K., & Dagher, A., Behavioral and Neural Valuation of Foods Is Driven by Implicit Knowledge of Caloric Content published in: Psychological Science

burgerscaleDo you want French Fries or salad with that?

How do people decide what to eat? Turns out, what we think of as an active and conscious choice may actually be a subconscious decision determined by specific regions of our brain. Researchers at McGill University have found that a person’s decision to consume food correlates, not with the perceived amount of calories, but with activation of specific parts of the brain that subconsciously estimate the caloric density (calories per gram of food) of a meal. This raises the question of whether calorie awareness influences our food choices. The results suggest that, while people are poor at estimating calories, our brains are wired to subconsciously identify familiar foods, with greater caloric density, as more desirable.

“In an increasing obesogenic food environment, these findings will expand our awareness and make us more conscious about the food we choose to eat, helping us in the fight against obesity.”* – Dr. Tang, main author of the study.

For this experiment, researchers designed a task to measure a person’s willingness to pay for things. Participants were shown different food items: low calorie items, such as fruits and vegetables, and high calorie items, such as candy and chips. They would then estimate the calories in each item without knowing the true caloric value, and place bids to acquire them.

Brain scan results indicated that the selection of the actual higher, not estimated, caloric meals correlated with the activation of the ventral medial prefrontal cortex (vmPFC). This activation may have led to larger bids from participants. Prior research has shown that the vmPFC is the area of the brain that encodes the value of stimuli and predicts immediate consumption.[1] The McGill study expanded on this finding by identifying subconscious, not conscious, estimates of caloric density of food as a determinant of willingness to pay and brain activity. How much a participant was willing to pay correlated with the true caloric intake of the meal, not with the estimated calories.

These findings suggest that while people are poor at judging the caloric content of food items, our brain is able to subconsciously assess the caloric content of familiar meals. This has been supported in previous studies where increases in calories, following food digestion, increases dopamine release in the brain.[2] Dopamine is the neurotransmitter responsible for motivation and associating actions with rewards. This dopaminergic signal may condition people to associate higher caloric foods with more reward. When people are uncertain about which food to eat, our brain is wired to estimate the calories in the meal and give preference to higher caloric foods, motivating us to choose certain foods over others. This paper expands our understanding of why people choose to eat high caloric, unhealthy meals that can lead to obesity. By understanding how our brain evaluates food and motivates us to eat, we can be more conscious of our food choices and hopefully say, “I’ll have a salad with that.”

For further information please read: Behavioral and Neural Valuation of Foods Is Driven by Implicit Knowledge of Caloric Content by Tang, D. W., Fellows, L. K., & Dagher, A. in the journal, Psychological Science.

Acknowledgements:

  • Tess Litchman – fellow classmate
  • Shyle Mehta – relationship: arch-nemesis, gym buddy, & friend
  • Cindy Stackhouse – relationship: mother

References:

  • Plassmann, H., O’Doherty, J., & Rangel, A. (2007). Orbitofrontal cortex encodes willingness to pay in everyday economic transactions. The Journal of Neuroscience, 27, 9984–9988. doi:10.1523/jneurosci.2131-07.2007
  • Ren, X., Ferreira, J. G., Zhou, L., Shammah-Lagnado, S. J., Yeckel, C. W., & de Araujo, I. E. (2010). Nutrient Selection in the absence of taste receptor signaling. The Journal of Neuroscience, 30, 8012–8023.
  • Tang, D. W., Fellows, L. K., & Dagher, A. (2014). Behavioral and Neural Valuation of Foods Is Driven by Implicit Knowledge of Caloric Content. Psychological Science, 25(12), 2168-2176. Retrieved March 4, 2016.

[1] Plassmann et al. ( 2007)

[2] Ren et al. (2010)

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