Treat Yourself: Connecting the Brain’s Reward System and Obesity

A silent killer lies among younger populations across the United States: childhood obesity. For children and adolescents aged two through nineteen, the prevalence of obesity stands at around 18.5%, with twelve to nineteen-year-olds being the most affected subset of that group. It is known that childhood obesity is a predictor of obesity later in life, and as such, previous work has largely focused on analyzing the relationship between rewards-related brain regions, unhealthy eating behaviors, and health outcomes. This led researchers at Yale University to focus on how the Nucleus Accumbens (NAcc)—part of the reward center of the brain—tissue microstructure can predict waist circumference after one year.

The study is based on data collected over the first year of a longitudinal study. In this ten-year Adolescent Brain Cognitive Development (ABCD) study, researchers across many institutions are currently following over twelve thousand nine and ten-year-olds. Researchers at Yale are following 5,366 in particular. The main hypothesis was built on existing data showing instances of neuroinflammation in the NAcc of animal models with diet-induced obesity.

In order to study this phenomenon in humans, researchers tracked the movement of water within the brain using magnetic resonance imaging (MRI) technology. This particular method is known as diffusion imaging, and it allows the user to functionally discern where water is being held within the brain, and, as a result, determine where there are higher cellular densities. By looking at the patterns of water movement, one can determine exactly which types of cells are found in that area. In this particular study, researchers focused on the glial (support) cells found in the NAcc. This conglomeration of cells can be attributed to an inflammatory response from the body. “This effect was not only massive, but it was very specific to this region (the NAcc),” Kristina Rapuano, a researcher focusing more on the neurological aspects of this research, remarked.

When the team followed up on their baseline participants a year later, there was increased waist circumference in 2,133 participants, which led them to believe that the increased amount of inflammation in the NAcc serves as a predictor of further weight gain in obese patients. The senior author of the paper, Richard Watts, expressed just how significant these findings were, specifically mentioning the traditionally smaller sample sizes available for MRI studies and how important it was to get this amount of data out of the baseline sample. Despite confounding factors that might contribute to both BMI and waist sizes, such as puberty, genetics, or socioeconomic background, the numbers nevertheless showed a strong correlation and should not be dismissed. These findings use data solely from the first year of the study. However, the second year of data has very recently become available. Researchers hope to gather further findings from this second set of data, as the first set did not make use of any MRI scans.

Both Watts and Rapuano emphasized that conclusions from this research are still speculative. “We can kind of look at it both ways. How is the weight gain driving the changes in cellularity in this area, and then how is that then further promoting weight gain?” Rapuano commented. Essentially, there is not one distinct resolution to this overarching relationship between obesity and the NAcc. In this way, using the most recent data, this team hopes to focus on how the participants’ NAcc tissue microstructure has changed (or not) within the past two years, and see how that correlates with changing waist measurements and body mass index (BMI) values. They hope to further strengthen the existing hypotheses mentioned above, and possibly puzzle together how all these parts come into play.

The bigger study which this particular study borrows from has its own long-term goals. To name some, the ABCD study plans to study the impacts on drug use, how these might play into the aforementioned reward systems, and overall quality of life. At the moment, we know of some of the negative effects of obesity – ranging from secondary health problems to struggles with mental health. Hence, in order to provide a better solution for such a high percentage of the population, we must better understand the many mechanisms at work. Hopefully, as time goes on, we will begin to understand the basis behind these behaviors that affect such a large portion of the population. 


Rapuano, K. M., Laurent, J. S., Hagler, D. J., Hatton, S. N., Thompson, W. K., Jernigan, T. L., . . . Watts, R. (2020). Nucleus accumbens cytoarchitecture predicts weight gain in children. Proceedings of the National Academy of Sciences, 117(43), 26977-26984. doi:10.1073/pnas.2007918117

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