Scientists have discovered how a molecule produced during physical exercise can suppress hunger signals in the brain, thereby promoting weight loss. This breakthrough could pave the way for new therapeutic treatments that offer similar benefits without the need for intense workouts.

How Lac-Phe Works

Researchers from Baylor College of Medicine (BCM) have thoroughly studied the pathway by which the metabolite N-lactoyl-phenylalanine (Lac-Phe), generated during physical activity, affects the brain. They found that Lac-Phe first influences one, then two different types of neurons, triggering a chain of events that leads to appetite suppression. While it was previously known that Lac-Phe could reduce appetite, the exact mechanism remained unclear.

Dr. Yan He, associate professor at BCM and co-author of the study, notes: “Regular physical exercise is considered an effective way to lose weight and prevent diseases associated with obesity, such as diabetes and cardiovascular conditions. Physical activity helps with weight loss by increasing energy expenditure, but other mechanisms are likely involved as well.”

The Significance of the Discovery

Understanding how Lac-Phe works is crucial for developing medications that could help people lose weight. The researchers focused on the brain, as it is the central regulator of appetite and eating behavior.

Lac-Phe is a metabolite whose levels rise sharply after intense physical exertion. It has been detected in humans, mice, and racehorses. Previous studies showed that administering additional Lac-Phe to mice reduced their food intake without negative side effects, confirming that the molecule acts as if it were naturally produced during exercise.

The Mechanism of Appetite Suppression

In their latest work, the team studied two types of brain cells in mice: neurons associated with agouti-related peptide (AgRP) in the arcuate nucleus of the hypothalamus, which stimulate hunger, and neurons in the paraventricular nucleus (PVN) of the hypothalamus, which help dampen hunger signals. These two neuron types form a system where AgRP neuron signals suppress PVH neurons, activating the sensation of hunger. When AgRP neurons are turned off, PVH neurons become more active and suppress appetite.

The researchers discovered that Lac-Phe directly blocks AgRP neurons, enhancing the activity of PVH neurons through a specific potassium channel sensitive to ATP (the KATP channel).

Dr. He explains: “We found that Lac-Phe acts on a protein in AgRP neurons—the KATP channel, which regulates cell activity. When Lac-Phe activates these channels, the cells become less active. If the KATP channels are blocked with drugs or genetic tools, Lac-Phe no longer suppresses appetite. This confirms that the KATP channel is essential for Lac-Phe’s effect.”

Potential Applications

Intense workouts, such as sprints or strength training, most effectively increase Lac-Phe levels, but even moderate activities like long bike rides can trigger its release. This discovery opens the possibility of using Lac-Phe as a supplement to activate the appetite-suppressing mechanism without the need for strenuous exercise.

Dr. Yun Xue from the University of South Florida notes: “The results also point to an exciting opportunity to target this newly discovered mechanism for weight control.”

Although the discovery was made in mice and requires validation in humans to determine if the effect is equally significant, it could offer a new approach to weight management without the gastrointestinal side effects typical of GLP-1 receptor agonist drugs.

Dr. Jonathan Long from Stanford University School of Medicine emphasizes: “This discovery is important because it explains how a naturally produced molecule can influence appetite by interacting with a key brain region that regulates hunger and body weight.”

The study was published in the journal Nature Metabolism.