Hunger Hormone Can Directly Impact Decision-Making Around Food, Study Suggests

New research from University College London (UCL) indicates that hunger hormones can directly impact activity of the brain’s hippocampus, driving an animal’s behavior around food. The study, published in Neuron, highlights the gut-brain connection and may help explain why some people are some susceptible to overeating.

"We all know our decisions can be deeply influenced by our hunger, as food has a different meaning depending on whether we are hungry or full,” said the study’s lead author, Andrew MacAskill, PhD, Principal Research Fellow in the Division of Biosciences at UCL. “Just think of how much you might buy when grocery shopping on an empty stomach. But what may seem like a simple concept is actually very complicated in reality; it requires the ability to use what's called 'contextual learning'.”

For their investigation, MacAskill and his colleagues sought to further explore how hunger hormones impact decision-making around eating. To do this, they observed mice in an environment with food, monitoring their behavior and brain activity with imaging in real time. The study focused on the ventral hippocampus, a brain region involved in decision-making and memory usage for guiding behavior.

The researchers found that a specific group of neurons in the ventral hippocampus became more active as the animals approached food, which prevented them from eating. However, in hungry mice, the activity in this area decreased, allowing them to eat. This change was linked to high levels of the hunger hormone ghrelin in the bloodstream.

Moreover, the University College London (UCL) researchers could manipulate this response. By activating the ventral hippocampal neurons, they made mice behave as if they were full, stopping them from eating even when hungry. This effect was also achieved by removing ghrelin receptors from these neurons.

Previous studies had indicated the presence of ghrelin receptors in the hippocampus of animals, including non-human primates, but their function was not well understood. This research demonstrates the role of these receptors, showing that the hunger hormone ghrelin can cross the blood-brain barrier and directly influence brain activity. This process controls a brain circuit likely similar to humans, researchers said, demonstrating the complex interplay between hunger, hormone levels, and brain activity in regulating eating behavior.

MacAskill said he hopes these findings encourage research on how ghrelin receptor in the hippocampus might be implicated in eating disorders, and whether similar mechanisms exist for stress or thirst.

"Being able to make decisions based on how hungry we are is very important. If this goes wrong, it can lead to serious health problems,” added the study’s first author, Ryan Wee, PhD, of the UCL Wolfson Institute of Biomedical Research. “We hope that by improving our understanding of how this works in the brain, we might be able to aid in the prevention and treatment of eating disorders."