Weaker Brain Connections Linked to Higher BMI:Study

A group of scientists may have discovered one reason why it’s easier for some people to stop eating when they’re full and more difficult for others.They say this may be caused by our sense of smell and neural reward systems versus negative feelings such as pain as well as the brain connection between the areas controlling those feelings. 

The study from researchers at Northwestern Medicine in Illinois states their theory is based on a newly discovered structural connection between two brain regions that appear involved in regulating feeding behavior. 

The researchers used neurological imaging from a large multi-center National Institutes of Health (NIH) project designed to map the human brain called the Human Connectome Project.The regions of the brain the study examined have been associated with sense of smell and behavior motivation.The researchers found that weaker connections between these two sensory regions, the higher a person’s body mass index (BMI), the researchers said. 

The areas under study connects the olfactory tubercle – part of the brain’s reward system associated with smell – and a midbrain region called the periaqueductal gray (PAG), which is involved in motivated behavior responding to negative feelings such as threat, pain and, potentially, eating suppression. 

Research has shown the smell of food is appealing when a person is hungry, but the odor becomes less attractive when that person eats the food until they’re full.The most recent study, published in the Journal of Neuroscience, reported that odors are important to guiding motivated behaviors such as eating and— in turn — olfactory perception is modulated by how hungry we are. 

However, researchers haven’t fully evaluated the neural underpinnings of how the sense of smell contributes to how much we eat.The desire to eat is related to how appealing the smell of food is — food smells better when you are hungry than when you are full.But if the brain circuits that help guide this behavior are disrupted, these signals may get confused, leading to food being rewarding even when you are full. 

The sensation of reward that comes with food could possibly, in turn, increase a person’s body mass index (BMI).When the structural connection between these two brain regions is weaker, a person’s BMI is higher, on average. 

The authors hypothesized that healthy brain networks connecting reward areas with behavior areas can regulate eating behavior by sending messages indicating eating doesn’t feel good anymore once that person is full.The researchers said that people with disrupted or weak connection circuits may not receive the stop signals and keep eating, even when they’re not hungry.Future studies will be needed to uncover the exact mechanisms in the brain that regulate eating behavior. 

Reference Link – Zhou, G., Lane, G., Kahnt, T., & Zelano, C. (2024). Structural connectivity between olfactory tubercle and ventrolateral periaqueductal gray implicated in human feeding behavior.

Retrieved from https://www.jneurosci.org/content/early/2024/05/09/JNEUROSCI.2342-23.2024