Ghrelin, the hunger hormone produced in the gut, directly shapes how the brain’s decision-making center works. Researchers at University College London conducted a study that was published in Neuron, shedding new light on how appetite signals influence choices about eating.
In a series of experiments, mice were placed in a space where food was available while scientists watched brain activity in real time. Every mouse showed interest in the food, yet only the hungry ones actually started eating. This setup helped reveal how hunger states alter the brain’s response to food cues.
It was observed that activity in the ventral hippocampus rises as the animals move toward food. This brain region is known to contribute to decision making, weighing options and controlling impulses. When a mouse was full, the increased hippocampal activity helped suppress feeding. Conversely, when a mouse was hungry, neural activity in this area dropped, reducing the hippocampus’s restraint on eating and allowing the animal to proceed with feeding.
The researchers also measured hormone levels and found that fasting increased ghrelin in the bloodstream. To test causality, they removed ghrelin receptors from nerve cells in the mouse brain, which made those cells unresponsive to the hormone. Under these conditions, the animals ate even when they were not physically hungry, illustrating ghrelin’s direct influence on brain circuits that govern hunger-driven behavior.
Earlier work had shown that ghrelin receptors exist in the hippocampus of animals, including primates. The current findings demonstrate that ghrelin can cross the blood-brain barrier and act directly on brain tissue. This linkage suggests that humans may share similar regulatory pathways for hunger, offering a potential key to better understanding eating disorders and how appetite is controlled in health and disease.
These results contribute to a growing view of how gut signals integrate with brain networks to shape decisions about food intake. By mapping the precise brain regions that respond to ghrelin and identifying how receptor activity modulates behavior, scientists move closer to decoding why people sometimes eat in response to cues rather than sheer hunger, and how to intervene when that response becomes maladaptive.
Understanding this gut-brain dialogue holds promise for developing targeted treatments that address abnormal eating patterns. If researchers can learn how to modulate ghrelin signaling or the hippocampal response, new strategies may emerge for addressing obesity, anorexia, or binge-eating disorders by aligning brain signals with bodily needs rather than external triggers.
As science continues to chart the path from gut hormones to brain circuits, the picture of appetite regulation becomes clearer. The study underscores a fundamental principle: hormones circulating through the body can reach the brain and steer complex decisions, often tipping the balance between restraint and action in the domain of eating.