Why You Lose Your Appetite When Sick: Scientists Decode the Gut-Brain Link

Researchers at University of California San Francisco have uncovered how infections trigger appetite loss by activating a communication pathway between the gut and the brain. The findings, published in Nature, reveal how the immune system influences eating behavior during illness.

The study shows that specialized gut cells called tuft cells detect parasites and release a chemical signal, acetylcholine. This signal activates nearby enterochromaffin cells, which then release serotonin. The serotonin stimulates the vagus nerve, sending signals to the brain that suppress appetite.

Interestingly, this process occurs in stages. Initially, a small burst of signaling occurs, but as the infection persists, tuft cells increase and release sustained signals—explaining why appetite loss often appears later during illness.

Experiments in mice confirmed the mechanism: those lacking this signaling pathway continued eating normally despite infection.

The discovery may also help explain digestive disorders like IBS and food intolerances, opening new avenues for treatment.

28-03-2026