What a Metabolic Medicine Physician Recommends for Vagus Nerve Health
By Dr. Lienna Wilson, Licensed Psychologist | Vagus Vitality
Most vagus nerve conversations center on breathing, cold exposure, or stress. But for a lot of people, the most direct daily experience of vagal signaling happens every time they eat. Appetite and fullness are read by the vagus nerve before they ever reach conscious awareness, and that mechanism is exactly what sits behind the Glucagon-Like Peptide-1 (GLP-1) medications, which are reshaping weight loss care.
To learn more about this topic, I had the pleasure of interviewing not only an expert in metabolic health but also a genuinely warm and caring person, Robert Fortino, DO. Dr. Fortino spends his days at the intersection of metabolic medicine and the gut-brain connection, so I sought his perspective on how gut health, appetite regulation, and the vagus nerve actually fit together. Dr. Fortino is a board-certified physician who runs medical weight loss and metabolic health clinics in Philadelphia and New Jersey, with a particular focus on GLP-1 based treatments.
How does gut health connect to nervous system regulation and stress resilience?
Dr. Fortino emphasizes that the gut is a major neurochemical signaling center, not just a digestive organ. Current research helps explain why: roughly 90 to 95 percent of the body's serotonin, and about half of its dopamine, are produced in the gut rather than the brain (Mawe & Hoffman, 2013). Neither of these gut-produced neurotransmitters crosses into the brain directly, but they influence mood and stress regulation indirectly, largely by acting on the vagus nerve itself. That's part of why gut issues, like an imbalanced microbiome or chronic digestive problems, so often show up as anxiety, low mood, or a harder time managing stress, not just physical discomfort (Cryan et al., 2019).
Another way of gut-brain communication happens through hormones released during digestion. As Dr. Fortino points out, specialized gut cells release hormones like cholecystokinin and GLP-1 in response to food and feeling full. These hormones activate vagus nerve sensory fibers that carry that information up to the brainstem (Bonaz et al., 2018). It is one of the clearest examples of how digestion and nervous system regulation are really the same conversation happening in two directions at once.
What role do GLP-1 medications and peptides play in gut-brain signaling?
This is where Dr. Fortino’s clinical world overlaps directly with the vagus nerve. Dr. Fortino explains that semaglutide, the active ingredient in Ozempic and Wegovy, is a GLP-1 receptor agonist. It binds to vagus nerve afferent fibers, which carry information from the gut to the brain. That way, it activates the same nerve pathway that would normally fire after a full meal, signaling to the brainstem that the stomach is full. That is a large part of how the medication reduces appetite. Tirzepatide (marketed as Mounjaro and Zepbound) works similarly but adds a second hormone pathway, acting on both GLP-1 and Gastric Inhibitory Polypeptide (GIP) receptors. Dr. Fortino also points to retatrutide, a newer medication still in development, which adds a third hormone (glucagon receptor) pathway on top of that.
Dr. Fortino also emphasizes an important distinction that's easy to miss in popular discussions of peptides: not every compound that affects the gut necessarily stimulates the vagus nerve. BPC-157, for example, is sometimes discussed for gut lining repair, but Dr. Fortino was careful to note that it does not appear to stimulate vagal tone the way GLP-1 medications do. It is a good reminder that “affects the gut” and “stimulates the vagus nerve” are not the same claim, even when a supplement or peptide is marketed as if they were.
Is there a specific diet you recommend for supporting gut and vagal health in your patients?
Although clinicians differ on the specifics of nutrition, Dr. Fortino's broader message is remarkably practical: build your diet around whole, minimally processed foods over anything designed to sit on a shelf indefinitely. Here is a check that I personally recommend: if your grandmother would recognize every ingredient in a dish, it's probably a good choice. If the label reads more like a chemistry set, full of preservatives and additives she wouldn't recognize, that's usually a sign to put it back.
Dr. Fortino particularly emphasizes foods that nourish the gut microbiome, including insoluble fiber, fermented foods, and foods that support short-chain fatty acid production. Examples of those foods might include leafy greens, fruits with edible peels, nuts and seeds, sauerkraut, kimchi, tempeh, miso, and apple cider vinegar.
Dr. Fortino is also particularly concerned about excess added sugar, which is easy to underestimate in a typical American diet. His concern reflects a much broader scientific consensus: consistently high intake of added sugar contributes to fatty liver disease, insulin resistance, chronic inflammation, and cardiovascular disease. It also raises blood pressure and drives chronic inflammation, both established pathways to heart disease. There's a gut-brain angle here too: sugary beverages in particular are easy to overconsume because liquid calories don't trigger the same fullness signals as solid food, quietly working against the same satiety pathways discussed earlier in this piece (Harvard Health Publishing, 2026).
Are there any practical habits you recommend for gut health?
Dr. Fortino places particular emphasis on the effects of modern environments on metabolic health, especially sleep disruption, blue light exposure, and electromagnetic fields. Among these, the evidence is strongest for the effects of poor sleep and nighttime light exposure on metabolism and appetite regulation. Poor sleep has a direct, well-documented effect on metabolism and weight. Sleep-deprived people tend to eat more, particularly more fat and carbohydrates, and their bodies shift toward hormone patterns that promote hunger and fat storage rather than fat loss (Papatriantafyllou et al., 2022).
Two of the biggest disruptors of good sleep are things most people interact with every night without thinking twice. Blue light from phones and screens suppresses melatonin and increases alertness right when your body should be winding down, which can throw off next-day glucose and insulin regulation (Fleury et al., 2020). Electromagnetic field exposure from devices close to your body before bed may also interfere with sleep architecture; one study found that phone-emitted EMF exposure before sleep altered REM latency and brainwave activity during early sleep (Loughran et al., 2005). Separately, a Kaiser Permanente cohort study found that higher magnetic field exposure during pregnancy was associated with increased obesity risk in the resulting children, suggesting EMF's reach into metabolic health may extend beyond sleep alone (Li et al., 2012).
The practical takeaway: treat your bedroom like a sleep environment, not an extension of your workday. Keep screens and phones away from the bed in the hour before sleep, keep the room dark and on the cooler side, and aim for a consistent sleep and wake time. None of this is exotic advice, but it is the foundation his more advanced metabolic treatments build on top of, not a replacement for it.
About Dr. Robert Fortino: Dr. Robert Fortino, DO, is a board-certified physician with more than 25 years of clinical experience. He runs medical weight loss and metabolic health practices in Philadelphia, PA, and Turnersville, NJ, where he specializes in GLP-1 based treatments, including semaglutide and tirzepatide, alongside broader metabolic and hormone health care. To learn more, visit www.DrFortino.net.
A note on medications and supplements mentioned here: GLP-1 medications like semaglutide and tirzepatide are prescription drugs that require medical supervision. Peptides like BPC-157 are not FDA-approved for any use. Nothing in this piece is a recommendation to start or stop any treatment. Talk to your own physician before making changes.
References
Bonaz, B., Bazin, T., & Pellissier, S. (2018). The vagus nerve at the interface of the microbiota-gut-brain axis. Frontiers in Neuroscience, 12, 49. https://doi.org/10.3389/fnins.2018.00049
Cryan, J. F., O'Riordan, K. J., Cowan, C. S. M., Sandhu, K. V., Bastiaanssen, T. F. S., Boehme, M., ... & Dinan, T. G. (2019). The microbiota-gut-brain axis. Physiological Reviews, 99(4), 1877-2013. https://doi.org/10.1152/physrev.00018.2018
Fleury, G., Masís-Vargas, A., & Kalsbeek, A. (2020). Metabolic implications of exposure to light at night: Lessons from animal and human studies. Obesity, 28(Suppl 1), S18-S28. https://doi.org/10.1002/oby.22807
Harvard Health Publishing. (2026, April 6). The sweet danger of sugar. Harvard Medical School. https://www.health.harvard.edu/diabetes-and-metabolic-health/the-sweet-danger-of-sugar
Li, D. K., Ferber, J. R., Odouli, R., & Quesenberry, C. P. (2012). A prospective study of in-utero exposure to magnetic fields and the risk of childhood obesity. Scientific Reports, 2, 540. https://doi.org/10.1038/srep00540
Loughran, S. P., Wood, A. W., Barton, J. M., Croft, R. J., Thompson, B., & Stough, C. (2005). The effect of electromagnetic fields emitted by mobile phones on human sleep. NeuroReport, 16(17), 1973-1976. https://doi.org/10.1097/01.wnr.0000186593.79705.3c
Mawe, G. M., & Hoffman, J. M. (2013). Serotonin signaling in the gastrointestinal tract: Functions, dysfunctions, and therapeutic targets. Nature Reviews Gastroenterology & Hepatology, 10(8), 473-486. https://doi.org/10.1038/nrgastro.2013.105
Papatriantafyllou, E., Efthymiou, D., Zoumbaneas, E., Popescu, C. A., & Vassilopoulou, E. (2022). Sleep deprivation: Effects on weight loss and weight loss maintenance. Nutrients, 14(8), 1549. https://doi.org/10.3390/nu14081549