A new study sheds light on the intricate relationship between body weight and reward processing in the brain. The findings, published in Brain Imaging and Behavior, provide evidence that individuals with obesity tend to have more pronounced brain responses to monetary rewards
Obesity is a global health concern with severe public health implications, affecting millions of people. It’s associated with a range of health problems, including heart disease, diabetes, and mental health issues. Researchers were motivated to conduct this study because they wanted to gain a deeper understanding of how our brains are involved in obesity and how they respond to rewards, like delicious food or even monetary incentives.
The new study focused on reward processing, which is how our brains react to pleasurable experiences. This includes the anticipation and enjoyment of things like a tasty meal or receiving a monetary prize. Previous research has shown that reward processing is closely linked to obesity. People with obesity often struggle with impulse control and have altered perceptions of rewarding food cues, which can lead to overeating.
“Obesity is a topic that fascinates us due to its implications in both physical and mental health,” said study author Maike Richter, a licensed clinical psychologist and member of the Translational Psychiatry research group at the Friedrich Schiller University Jena. “We aim to gain a deeper understanding of the neural pathways and mechanisms that are associated with obesity. Reward processing is of particular interest in this regard, as it has consistently been associated with obesity and may lend itself well to concrete avenues for behavior change interventions.”
To dig deeper into this connection between the brain and obesity, the researchers examined specific brain regions known to be involved in reward processing. These regions include the insula, orbitofrontal cortex (OFC), and striatum. They are part of what’s called the “hedonic pathway,” which plays a vital role in our experiences of pleasure and reward.
The insula is known for its role in hunger regulation, emotional processing, and craving, making it a particularly intriguing region for studying reward processing in relation to obesity. The OFC is involved in decision-making and valuing specific rewards, such as tasty foods. The striatum, which includes the nucleus accumbens, caudate, and putamen, is associated with reward anticipation and general pleasure.
The study involved 383 participants recruited in Germany as part of the Münster Neuroimaging Cohort. These participants underwent functional magnetic resonance imaging (fMRI) while engaging in a card guessing game designed to simulate reward processing.
During the game, participants had to make guesses, and they received either monetary rewards or no rewards based on their choices. This setup allowed the researchers to observe how the participants’ brains reacted to the prospect of winning rewards and how these reactions were related to their body mass index (BMI), a measure of body weight relative to height.
The researchers discovered a significant positive relationship between BMI and insula activation. In simpler terms, the more overweight a person was, the more their insula region responded when presented with the possibility of a reward. This finding suggests that the brains of individuals with higher BMIs might be more sensitive to rewarding stimuli.
“The major take away from our study should be that the brains of people with obesity respond more strongly to rewards (money, not just food rewards!) than those of people within the normal weight range,” Richter told PsyPost. “This finding supports previous studies that found aberrations in brain volume in areas that process rewards in participants with obesity.”
Interestingly, when the researchers excluded participants with obesity from their analysis, the link between BMI and heightened reward responses disappeared. This indicates that the connection between body weight and reward processing may be more pronounced in individuals with clinical obesity, rather than those with less severe weight issues.
“Although we found a linear association between BMI and reward response, we were surprised to discover that this association appeared to be mainly driven by participants with obesity,” Richter said. “Changes in brain structure (as opposed to function) have been uncovered across the weight spectrum, so it was surprising that aberrant reward processing seemed to be specific for participants with obesity (BMI over 30).”
The implications of this research are promising, as they open the door to more personalized and effective interventions for obesity. By better understanding how our brains respond to rewards, scientists may unlock new ways to address this pressing public health issue. Nonetheless, it’s crucial to acknowledge the study’s limitations and the need for continued research to uncover the full story behind the brain’s role in obesity.
“This was a cross-sectional study,” Richter explained. “We do not yet know whether an over-responsiveness to rewards is a factor that makes people more prone to overeating and therefore developing obesity, or whether it is a consequence of having obesity. This should be addressed in future longitudinal research with several times of measurement.”
The study, “Higher body weight-dependent neural activation during reward processing“, was authored by Maike Richter, Sophia Widera, Franziska Malz, Janik Goltermann, Lavinia Steinmann, Anna Kraus, Verena Enneking, Susanne Meinert, Jonathan Repple, Ronny Redlich, Elisabeth J. Leehr, Dominik Grotegerd, Katharina Dohm, Harald Kugel, Jochen Bauer, Volker Arolt, Udo Dannlowski, and Nils Opel.
