Is your brain bigger than your stomach? Understanding obesity and your preference for high-calorie foods

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.


Have you ever wondered why you gravitate towards certain foods over others at the buffet table? What makes one food more attractive than the next? Turns out that caloric density determines your assessment of a food item’s value. In other words: your brain is choosing what you want to eat. And it is not gravitating towards that green salad with a single radish on top. It is choosing that high-calorie candy bar or hamburger.


A recent study conducted at McGill University suggests that we judge the reward value of a food based on the implicit knowledge we have of its caloric content. If your brain knows a food is calorie-dense, it will tend to favor it over its low-calorie counterpart. The experiment provided 29 normal-weight and healthy individuals with pictures of 50 well-known foods. Participants were asked to bid for the different food items, so as to measure the value they allocated to each one. The results showed a connection between higher prices and higher caloric densities. The foods participants were valuing and determining as being more expensive were in fact those with higher calorie counts.

The experiment didn’t stop there. Functional magnetic resonance imaging (fMRI) was used to take a closer look at the ventromedial prefrontal cortex (vmPFC) part of the brain, where a value is assigned to stimuli such as foods. Results from the fMRI showed activity in the vmPFC when it came to evaluating the different pictures of food: caloric density, once again, seemed to be the criteria used in the evaluation of food.

Surprisingly, participants were bad at consciously judging and estimating the caloric content of foods. This however does not take away from the fact that there exists an implicit knowledge of caloric content in each one of us. Our food choices depend on the food choices we have made in the past: if we experienced a greater reward from eating a particular food, for example a boost in energy due to high calorie content, then we will gravitate towards that food in the future. The difficulty we have in estimating how many calories are in a given food does not impede our capacity to almost systematically choose high-calorie foods over low-calorie ones.

What does this mean for us, for you? The authors of the study explain that these systems “are absolutely key in understanding today’s obesity epidemic”*, being that “high-calorie foods are highly available in our environment and as we are programmed to value these foods over others, we overindulge and beef up”*. They urge us to watch out because the only thing that can save us from falling into unhealthy and destructive eating habits is awareness of how our brain systems are designed to work against us. You don’t need a doctorate in neuroscience to understand your natural tendency to prefer high-calorie foods. Remain aware, eat balanced, and don’t let your vmPFC get between you and those skinny jeans.

Giselle Torres and Daniel Froot, friends of mine and fellow Class of 2016’ers. Both provided helpful feedback by suggesting I simplify and explain some of the scientific jargon I had initially included in the press release.

(n.d.). Photo retrieved from

(n.d.). Photo retrieved from

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.