Scientists Discover Brain Mechanism That Signals the Body to Stop Eating

What if the key to feeling full isn't just in your neurons-but in overlooked brain cells working behind the scenes?

A new study published in Proceedings of the National Academy of Sciences is reshaping how scientists understand appetite control, revealing that astrocytes—once thought to be mere support cells-play an active role in telling the brain when to stop eating.

The research, led by teams from the University of Concepción and the University of Maryland, uncovers a previously unknown communication pathway in the hypothalamus, the brain’s hunger-regulating center.

Traditionally, neurons were considered the main players in signaling hunger and fullness. However, this study shows a more complex chain of events involving multiple cell types. After a meal, rising glucose levels are detected by specialized cells called tanycytes. These cells convert glucose into lactate, which then acts as a signaling molecule.

Instead of communicating directly with neurons, lactate first activates nearby astrocytes through a receptor known as HCAR1. Once activated, astrocytes release glutamate, a neurotransmitter that signals appetite-suppressing neurons, ultimately creating the sensation of fullness. In simple terms, tanycytes “talk” to astrocytes, and astrocytes “talk” to neurons.

Researchers also found that this signaling can spread across networks of astrocytes, amplifying the brain’s response to food intake. Interestingly, lactate may have a dual role—indirectly activating fullness signals while also potentially suppressing hunger signals through other pathways.

Scientists are now exploring whether manipulating the HCAR1 receptor could influence eating behavior. If successful, this pathway could complement existing treatments like Ozempic, offering a new frontier in metabolic health.

REFERENCE: S. López,R. Elizondo-Vega,V. Azócar,V. Sepúlveda,V. Opazo-Mellado,W. Vásquez,J.C. Sáez,R.C. Araneda, & M.D.L.Á. García-Robles, Tanycyte-derived lactate activates astrocytic HCAR1 to modulate glutamatergic signaling and POMC neuron excitability, Proc. Natl. Acad. Sci. U.S.A. 123 (15) e2537810123, https://doi.org/10.1073/pnas.2537810123 (2026).