New research from The University of Manchester is changing how scientists think about the link between fasting and the immune system.
The study, which was done in mice and published in Science Immunology, suggests that it’s not just the lack of food that affects our immune response during fasting—but the brain’s perception of hunger itself.
For a long time, researchers believed that fasting helps the immune system mainly because the body isn’t getting nutrients.
But this new study shows that the brain plays a much more active role. Specifically, the hypothalamus—a part of the brain that controls hunger—can signal the immune system to change, even when there’s no actual lack of food.
In the study, scientists used a special technique to “turn on” specific neurons in the brains of mice.
These neurons normally become active when energy levels are low and the animal feels hungry.
When the researchers triggered this artificial sense of hunger, they saw the mice’s immune systems react the same way they would if the mice were really fasting. Within just a few hours, immune cells in the blood began to shift.
There was a sharp drop in inflammatory monocytes, which are immune cells that increase during illness or injury.
In other words, the mice looked like they were fasting—even though they weren’t. Their immune systems responded not to what they had eaten, but to what their brains believed.
This discovery is important because it shows that the brain, not just diet or nutrition, can have a strong influence on the immune system.
It might help scientists understand more about conditions like obesity, where inflammation is common, or wasting syndromes in cancer patients, where people lose weight even if they are still eating.
It might also explain why people who are malnourished are more prone to infections and inflammation.
Dr. Giuseppe D’Agostino, who led the study, said this research highlights how deeply connected the brain and body are.
He noted that while we often think of the brain guiding our actions, this study shows it also plays a key role in invisible internal changes—like how our immune system responds to hunger.
Professor Matt Hepworth, an immunologist involved in the study, said the findings challenge the long-standing idea that it’s only the lack of nutrients during fasting that affects the immune system. Instead, the nervous system, especially the brain, has a major role.
Lead author Dr. Cavalcanti de Albuquerque added that understanding this connection opens the door to exploring how fasting could benefit health—and how brain signals might be used to treat diseases related to the immune system, metabolism, and even mental health.
If you care about brain health, please read studies about dietary strategies to ward off dementia, and how omega-3 fatty acids fuel your mind.
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