Can Feeling Hungry Extend Your Lifespan? Shocking Discoveries by Science and Its Subsidiaries: "Hunger" Isn't Simple, It Can Reshape Immunity and Extend Lifespan, Regardless of How Much You Eat

These days, many young people seem to have a "self-disciplined" approach to weight loss. They skip dinner, avoid milk tea and fried chicken, and survive on clear soups and plain water. While munching on lettuce, they proudly post their "calorie deficit" achievements on social media. To them, enduring hunger seems like the key to successful weight loss, reminiscent of modern-day ascetic monks.

However, the significance of this "hunger endurance" goes far beyond just losing weight. Increasingly, research shows that the feeling of hunger triggers a powerful "self-improvement" mechanism in the body. Not only does it aid in weight loss, but it also enhances immunity and slows down aging, making it a hidden gem in the world of health and wellness.

## The Brain's Role in Hunger: Directing the Immune System to "Tighten Its Belt"

Recently, a research team from the University of Manchester published a study in *Science Immunology* revealing a surprising secret behind feeling hungry: the brain's perception of hunger can directly influence the dynamics of peripheral immune cells, independent of actual energy levels in the body. In other words, just feeling hungry can trigger changes in the immune system.

Typically, we think that changes in nutrients (like glucose and amino acids) during hunger or feeding states indirectly affect the immune system by regulating the metabolic activity of organs. However, this study presents a groundbreaking discovery: the brain's perception of hunger and fullness can regulate peripheral immune cells without relying on actual energy states.

This finding stems from scientists' long-standing curiosity about a phenomenon: when humans or mice fast for extended periods (e.g., 20 hours), the blood levels of a type of immune cell called Ly6Chi monocytes significantly decrease. These cells are like the "first responders" of the immune system, quickly rushing to sites of infection or tissue damage to clear pathogens and damaged tissue. However, in some chronic inflammatory diseases like atherosclerosis, metabolic syndrome, and certain cancers, these cells can become overactive, causing tissue damage and worsening the condition.

So, does the decrease in these cells occur because the body is low on "fuel," forcing the immune system to "tighten its belt"? Or does the brain, sensing hunger, send signals to suppress the immune response? The researchers decided to investigate this directly.

The study found that even when nutrients are not lacking, the mere perception of hunger by the brain triggers an immune response. It's as if the body "thinks it's full" and relaxes its defenses, allowing Ly6Chi cells to become active again.

This reveals that AgRP neurons, the "masterminds" behind hunger, have the ability to regulate the immune system. When activated, these neurons prompt an immediate response from the immune system, leading to a rapid decrease in Ly6Chi monocytes in the peripheral blood. But knowing that activation is useful isn't enough; researchers also wanted to see if deactivating these neurons would affect immune cell responses.

The results showed that without AgRP neurons, even basic hunger responses are impaired. This indicates that the normal activity of AgRP neurons is crucial for regulating immune cell numbers. In other words, while hunger can reduce immune cell numbers, this effect is not simply due to a lack of energy.