Encore: Your Nervous System Controls Your Gut, Hormones, and Weight — Here's How to Fix It

You've cleaned up your diet. You're taking the supplements. You're exercising, sleeping more, and doing everything "right." So why do you still feel exhausted, inflamed, anxious, or stuck? In this encore episode—one of the most impactful Office Hours conversations we've shared—I explore a question that could change the way you think about healing: What if your nervous system is the missing piece? When your body doesn't feel safe, it prioritizes survival over repair, affecting everything from your metabolism and hormones to your gut, immune system, and brain. In today's episode, I break down: Why chronic stress changes your biology—and how nervous system dysregulation can drive inflammation, hormone imbalance, digestive issues, weight gain, and autoimmune disease The difference between living in constant "fight-or-flight" versus a regulated nervous system that supports healing, resilience, and recovery Simple, science-backed strategies to regulate your nervous system, including breathwork, blood sugar balance, strength training, sleep, and daily safety cues Why you can't out-supplement or out-biohack chronic stress—and how creating physiological safety unlocks your body's natural ability to heal Healing isn't just about finding the right supplement or following the perfect diet. It's about creating an environment where your body feels safe enough to repair itself. When you begin working with your nervous system instead of against it, everything else—from your energy and metabolism to your mood and resilience—can start to change. Check out my full conversation with Dr. Scott Sherr HERE. Track your health with Function Health: https://functionhealth.com/mark (Use code MARK2026 for $50 off your membership.) Have a question you’d love answered on Office Hours? Submit it here Resources Mentioned: Listen to my full conversation with Dr. Scott Sherr on nervous system regulation and mitochondrial health.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Dr. Mark Hyman?

  So yes, nervous system regulation may be the missing piece because you can't outsupplement chronic stress signaling. You can't biohack your way out of a body that feels unsafe. Healing requires physiological safety. Welcome back to Office Hours. As part of our summer replay series, we're revisiting some of the conversations that sparked the biggest response from our audience. And this one is one that clearly struck a nerve. Many of us spend years trying to optimize our health. We clean up our diet, we take supplements, we improve our sleep, and run every imaginable test. Yet sometimes we feel stuck. What made this episode resonate with so many listeners is that it explores a different question altogether. What if the issue isn't your gut, your hormones, or your metabolism? What if the real problem is that your body truly

• 0:43Dr. Mark Hyman?

  never feels safe enough to heal? In this conversation, I unpack the powerful role of the nervous system in regulating everything from inflammation and blood sugar to digestion, sleep, mood, and recovery. It's a perspective that has become increasingly important and one that many people find surprisingly relevant to their own health journey. Whether you're hearing it for the first time or coming back for another listen, I think you'll find yourselves looking at stress, resilience, and healing in a completely different way. Let's dive in. This episode was brought to you by Function. Get access to over 160 lab tests annually at functionhealth.com/marc. Today, I want to talk about something that might be the basic link in your health. You clean up your diet, you're taking your supplements, you're trying to sleep more,

• 1:23Dr. Mark Hyman?

  maybe even run labs and to work with practitioners. But maybe you're still wired, or exhausted, or inflamed, or just stuck in your health. What if your issue isn't your gut, your hormones, or your metabolism? What if the real issue is your nervous system? Because here's the truth. Your body cannot heal if it thinks it's under threat. So today, we're going to unpack what nervous system regulation actually means, and what a regulated nervous system looks like, and whether calming your internal stress response might be the key that unlocks healing. This isn't just about stress management, it's about biology. When I was in training to learn all about this stuff after medical school, because that was just the beginning, I took a course with a guy named Herbert Benson.

• 2:06Dr. Mark Hyman?

  And he said that stress either causes or worsens 95% of all illness. That's a big deal and we should pay attention to that. In functional medicine, we talk a lot about inflammation. We talk about insulin, we talk about hormones, we talk about toxins, all important. But underneath all of it is one master regulator, your nervous system. So what is your nervous system really? Let's simplify this. You have two main branches of your nervous system. The sympathetic system, which is fight or flight, and the parasympathetic system, which is the rest, digest and repair, the relaxation nervous system. Now, the sympathetic system mobilizes you. It makes your heart rate go up, it raises your blood sugar, it redirects energy away

• 2:47Dr. Mark Hyman?

  from digestion and primes you for action, running from a tiger or getting in a fight. Not bad if you're surviving, it's essential. But the parasympathetic system is where healing happens. It's where digestion happens, where detoxification happens, where hormone regulation happens, where immune repair happens. And then there's the vagus nerve, which is a major communication highway between your brain and your body. It connects your brain to your gut, to your heart, to your lungs, to your immune system. So when we talk about nervous system regulation, we're really talking about your body's ability to shift fluidly between activation and recovery. The key word is how to be adaptable here, or adaptability. Regulation doesn't mean being calm all the time.

• 3:30Dr. Mark Hyman?

  It means you can experience stress and then return to baseline. There's a great book called Why Zebras Don't Get Ulcers by Robert Sapolsky, who's one of the key scientists who's helped us understand stress. And the reason zebras don't get ulcers is because when the lion chases them, they run like hell, freaked out. The lion catches one of the zebras, then goes about eating it. And all the other zebras just stop running and they stand around the lion while it's eating another zebra. And they, their nervous system just calm right down. That's why they don't get ulcers. We just stay chronically stressed all the time. Now, the critical insight from functional medicine is this. Your nervous system sets the tone for every other body system. So what is dysregulation of your nervous system actually look like?

• 4:14Dr. Mark Hyman?

  Well, most people don't realize they're dysregulated because it just feels normal. Let me paint you a picture. If you're chronically in sympathetic mode, that's sympathetic nervous system activation, stress response. You might experience a lot of things. You might feel tired, but wired. You might be anxious and irritable. You might have digestive issues, constipation or diarrhea, irritable bowel syndrome. You might have blood sugar swings. You might get panic attacks. You might wake up at two or three in the morning. You might have belly fat that won't budge. Here's a little tip for you. Your nervous system is connected to your fat cells. And this is actually scientifically true. I've written about it in my books.

• 4:58Dr. Mark Hyman?

  The nervous system innervates fat cells or adipose tissue. And when you're stressed, it makes them get more fat. It makes you gain more weight. That's not a good thing. It also affects hormone swings, autoimmune players. We know that just actually regulating your vagus nerve, they can regulate their vagus nerve through various implantable devices now and cure rheumatoid arthritis. There was a study that I wrote about years ago where people who just journaled, who had rheumatoid arthritis for 20 minutes a day about their authentic feelings, had a dramatic reduction in symptoms, better than most medications. Also, chronic stress raises cortisol. It causes then elevations in blood sugar. Cause you know, when you're stressed, you want to have high blood sugar, but not all the time.

• 5:42Dr. Mark Hyman?

  And then when you have high blood sugar, you become insulin resistant. And when you become insulin resistant, that causes inflammation. Then when you have inflammation, that disrupts your hormones even more. It causes gut damage. It causes changes in your immune system. Now you're chasing symptoms. When the upstream driver is your stress signaling response. Now, on the other side, some people swing into what we call vagal shutdown. This is the freeze response. What does that look like? Well, fatigue, brain fog, low motivation, depression, feeling numb and disconnected. Many people bounce between both states, wired and exhausted at the same time. So tired and wired, it's not weakness, it's just nervous system dysregulation. So what does regulation actually look like?

• 6:25Dr. Mark Hyman?

  What does it look like to have a regulated nervous system? It's not constantly being calm, it's resilience. Now, regulated nervous system means you can handle stress without spiraling. You can digest your food well, you can sleep deeply, your mood's relatively stable, your heart rate variability improves, you recover faster from setbacks. Regulation is about recovery speed. It's about flexibility, it's about metabolic safety. Because when your body feels safe, it turns on the repair system. When your body feels threatened, well, it prioritizes survival. And survival mode means shutting down long-term healing. Okay, so could this be the missing link to healing that we've been looking for? Well, let's connect the dots.

• 7:06Dr. Mark Hyman?

  If you're trying to heal your gut, but you're chronically stressed, well, your microbiome shifts in response to the stress hormones. So you literally change your microbiome with stress. If you're trying to balance hormones, but cortisol is elevated, it steals from the progesterone and other pathways that regulate your sex hormones. You're trying to lose weight and you're in constant fight or flight, well, your insulin stays high. If you're dealing with autoimmunity, well, stress directly affects immune signaling and your immune system's health. So yes, nervous system regulation may be the missing piece. Because you can't out-supplement chronic stress signaling, you can't biohack your way out of a body that feels unsafe. Healing requires physiological safety. How do you regulate your nervous system? Let's make this practical. Number one, stabilize your blood sugar.

• 7:52Dr. Mark Hyman?

  Unstable blood sugar is interpreted as a threat. And let me tell you how to do that. Start your day with protein, really important. Balance every meal with protein, healthy fat and fiber. Reduce, or I don't even like the word reduce, I would just say never eat ultra-processed food. There's no reason to eat Twinkies or Pop-Tarts or Lunchables or Gogurts or any of the million things that are in the grocery store shelves that are not actually food. Just eat food, listen to Mike Tyson, eat real food. This alone dramatically calms your stress signaling. Next, use your breath. One of the fastest ways to shift into the relaxation response to the parasympathetic mode is your breath. So you can try this, just inhale through your nose. And then take a second short inhale and then exhale fully and slowly through

• 8:37Dr. Mark Hyman?

  your mouth. That long exhale activates your nervous system. I just did it. I feel relaxed already. Two minutes can change your state. Literally, just try even five breaths can change your state. Just do five deep breaths, profound and rapid change. You always have that accessible to you. To keep your skin in check this summer, you have to check your health. I know that's not what you're used to hearing, but after decades in medicine, you need to know this. The glow you're chasing doesn't start with creams and serums. It starts in the blood. Your skin is an organ. In fact, it's your largest organ. And like everything else inside your body, your skin health depends on your nutrient status, your inflammation levels, your liver function, even your environment. So you can spend money on the latest treatment, or you can look beneath the surface to get to the source. That's exactly why we built

• 9:21Dr. Mark Hyman?

  Function. Function gives you access to 160 plus lab tests annually that measure signals in your blood, including nutrients, liver health, inflammation, and hormones. You can also complete your health baseline with an annual MRI that helps you see organs, tissues, and other changes. Check your health at functionhealth.com/marc. And if you're one of the first 1,000 people this week, use the code MARC2026 for a $50 credit or your $365 a year membership. Next pro tip is build muscle. Muscle isn't just about looking good or aesthetics. It improves insulin sensitivity and increases mitochondrial density, but it also enhances stress resilience. So strength training is one of the most powerful nervous system stabilizer we have because muscle is your metabolic armor. Next, protect your sleep because when

• 10:05Dr. Mark Hyman?

  your sleep is not good, you're in trouble. Sleep is when your body and your nervous system recalibrates. So how do you fix your sleep? Get morning light exposure. Sleep at a consistent bedtime. Not always ideal, but can. Reduce your evening stimulation. So don't do stimulating things right before bed. Avoid blood sugar crashes before bed. Because meaning don't eat a lot of sugar and starch at dinner. If you don't sleep, you can't regulate. So make sure you prioritize sleep. Next, you want to create safety cues. The nervous system responds more to cues of safety than to positive thinking. So what is that? Nature, connection, community, touch, laughter, time offline, which I love.

• 10:50Dr. Mark Hyman?

  Your biology is always scanning for safety. Just give it those signals. They're available to you. All right, what are the myths about nervous system regulation? And when it comes to nervous system function? Is nervous system regulation just meditation? No, it's metabolic, it's relational, it's physiological. If I'm productive and high achieving, I must be regulated. Not necessarily. I'm an example of that. You may be, as you're running on adrenaline, which I did for many years. Can I biohack my way out of stress? Well, not if your lifestyle stays chaotic. If I calm down, I lose my edge. Well, actually, regulation improves focus, performance and clarity. So you do better. So here's the bottom line. A regulated nervous system is not a luxury. It's the foundation of healing.

• 11:36Dr. Mark Hyman?

  If you feel stuck, whether it's weight gain, hormone dysfunction, gut issues, inflammation, just ask yourself, does my body feel safe? Because healing happens in safety. So start small. Balance your breakfast, lift something heavy, breathe for two minutes. Every morning I wake up and I do a breathwork practice for five minutes. It's amazing. I love starting my day like that. Go outside, get some fresh air, get some sunlight. Prioritize your sleep. You don't heal by fighting with your body. You heal by teaching it that it's safe to repair. And when you do that, everything changes. Now, if you want to go deeper, I want you to keep an eye out for my upcoming episode on my podcast with Dr. Scott Shear. We're exploring the emerging theories and the practical tools for regulating nervous

• 12:21Dr. Mark Hyman?

  system and unlocking the body's healing capacity. Take a listen to this short clip from our conversation. Today, I really want to like have people who are listening to understand, you know, what, what is going on with their, their energy? What is going on with stress? What, what are the psychological and the physiological? Logical cause of stress. And how do we start kind of navigating this from a therapeutic perspective? Because like, we all want out of this. I, as soon as like, yeah, I'm in this sympathetic spiral of doom, and I want the hell out of this thing. So what is it? Explain it to us. Unpack it for us.

• 12:53Speaker 01

  Well, thanks again for having me, Mark. And you know, what I, what I like to just describe here is it's not a diagnosis for people. This is more of a pattern. As you mentioned, it's an age old pattern, but I realized recently that it was really a significant discovery for me to understand that it's a spiral and it's a loop. You have sympathetic activation, which is your fight or flight, your nervous system being activated. You have mitochondrial dysfunction. Mitochondrial dysfunction, mitochondria, as all your listeners know, is a part of our cells that make energy. The combination of sympathetic activation, mitochondrial dysfunction, is a loop. And what happens here is that this loop can either start with mitochondrial dysfunction directly, that's what I call bottom up, or it can start with sympathetic activation from outside stressors. Say it's your job, your

• 13:37Speaker 01

  relationship, you have a snoring partner that is snoring and you can't get to sleep at night. Outside stresses, or even like worse things like trauma, or things that happen when you were younger, that have maintained you in this place where you can't stay safe. Either way, whether it starts with mitochondrial dysfunction directly, or it starts with sympathetic activation externally, or for most people, it's both. And then it's something that just makes you fall off a cliff. It could be

• 14:00Dr. Mark Hyman?

  Let me pause you for a sec. Just define sympathetic activation. Because people are like, what is that? And define like, a little bit better mitochondria. Because these are, these are central to your thesis of sympathetic. So let's get our terms right. Because I think if you're like

• 14:14Speaker 01

  Otherwise, I'd be just be talking doctor

• 14:16Dr. Mark Hyman?

  I'm sympathetic, you know, I'm sympathetic. No, no, it's not that.

• 14:19Speaker 01

  Yeah, no, good point. So yeah, so I put them sympathetic to those that are insympathetic. The sympathetic nervous system, so sympathetic is your fight or flight, part of your nervous system. So it's your, it's running away from the proverbial saber tooth tiger, as we somehow always refer to. I don't know why. But you're getting chased by something. But unfortunately, we're getting chased all the time in modern society, whether it's with our phones that are actively in our faces all the time, and doom scrolling at three o'clock in the morning, going, why is this the way it is? Or it's outside things like your job, your relationship, but we're not We don't reward people resting and relaxing. So the sympathetic nervous system is part of your autonomic nervous system. You have your sympathetic branch, which is your activation, fight or flight.

• 15:01Speaker 01

  And you have your parasympathetic, which is your rest, digest, detoxify and heal. But modern society doesn't reward that side, right? It rewards the hustle. I mean, in medical school, my friends and I had shirts that said, sleep is for quitters.

• 15:15Dr. Mark Hyman?

  Yeah.

• 15:15Speaker 01

  Not surprising.

• 15:16Dr. Mark Hyman?

  That's right.

• 15:16Speaker 01

  I grew up in New York.

• 15:17Dr. Mark Hyman?

  Surgeons don't have lunch. That was ours.

• 15:19Speaker 01

  There you go. Same kind of thing. Like you just, you hustle, right? You go and you grind, right? That's what we reward. And then unfortunately, that's how society has created this stress externally for us that we have to perform, we have to have more meetings, we have to do more, do more, do more all the time. And so instead of just running away from the saber tooth tiger and then, you know, hanging out the rest of the day because hopefully we lived, maybe we probably didn't, but in some cases we did, right? Then you would have the time to relax because your nervous system would be activated and then it'd be shut off. But that's not how modern society works anymore, as you know. We're constantly stressed, constantly on pressure, constantly on meetings. And that's that sympathetic activation. And most of us kind of think we thrive in that, in that environment. And we can for a little while.

• 16:03Speaker 01

  But the problem is that when you're sympathetic all the time, you're releasing hormones like cortisol, your neurotransmitters like norepinephrine and epinephrine.

• 16:10Dr. Mark Hyman?

  Adrenaline.

• 16:10Speaker 01

  And adrenaline, yes. Noradrenaline, adrenaline that are stimulating the whole system to work harder. Because if you're in that sympathetic nervous system activation all the time, I call it sympathetic overdrive. You're just shoving all those neurotransmitters and hormones out all the time. And that causes deterioration in immune system function, in hormone function and in your mitochondria itself. So to define mitochondria, which we can do now.

• 16:32Dr. Mark Hyman?

  Yeah.

• 16:33Speaker 01

  The mitochondria are part of the cell that helps make energy, right? When I was in high school, my, my daughter is in ninth grade. She learned, she's got the, the basic cell. She just learned, she's like, dad, check out the basic cell. It's got a nucleus, it's got cytoplasm, it's got Golgi bodies. And it's got this one little cool organelle called a mitochondria. I'm like, huh, this is what I learned when I was probably that age too.

• 16:52Dr. Mark Hyman?

  Yeah.

• 16:52Speaker 01

  You learn that cell has one mitochondria, but that is far from the case.

• 16:56Dr. Mark Hyman?

  It has like thousands.

• 16:57Speaker 01

  Some cells in our body have thousands of mitochondria per cell. And some cells, actually there's one human cell that has zero. And that's the red blood cell.

• 17:03Dr. Mark Hyman?

  Yeah, the red blood.

• 17:04Speaker 01

  Right. But most mitochondria per cell are in our reproductive organs. Eggs, oocytes, sperm are the number one and number two.

• 17:11Dr. Mark Hyman?

  They gotta swim, they need a lot of energy to swim.

• 17:13Speaker 01

  Yeah. And the eggs have more though. Women have to, you know, create, make the baby. And so they have more. But then just behind that is your brain, your heart. Your liver, your musculoskeletal tissue. So detox, everybody is hugely energetically intensive.

• 17:26Dr. Mark Hyman?

  Liver, yeah.

• 17:26Speaker 01

  People don't realize that is like if you need it, if you're going to be able to detox, you have to have a huge amount of mitochondrial energy.

• 17:32Dr. Mark Hyman?

  So you remember, you are not powerless in this process. You have far more influence over your biology than you've been told. When you learn to work with your nervous system instead of against it, you take back control of your health and that's where real transformation begins. Thanks for joining me for office hours. I love diving into these topics with you. Remember, you are the CEO of your own health and every choice you make can move you closer to healing and vitality. I want to keep these episodes as relevant and useful as possible. So tell me, what do you want to explore next? What questions are you wrestling with? What breakthroughs are you chasing? Share your ideas in the comments on social media or through the link in the show notes. I'm listening. Until

• 18:15Dr. Mark Hyman?

  next time, keep taking charge, keep asking questions and keep showing up for your health. If you love this podcast, please share it with someone else you think would also enjoy it. You can find me on all social media channels at Dr. Mark Hyman. Please reach out. I'd love to hear your comments and questions. Don't forget to rate, review and subscribe to the Dr. Hyman Show wherever you get your podcasts. And don't forget to check out my YouTube channel at Dr. Mark Hyman for video versions of this podcast and more. Thank you so much again for tuning in. We'll see you next time on the Dr. Hyman Show. This podcast is separate from my clinical practice at the Ultra Wellness Center, my work at Cleveland Clinic and Function Health where I am Chief Medical Officer. This podcast represents my opinions and my guests' opinions. Neither myself nor the podcast endorses the views or statements of my guests. This podcast is for educational purposes only

• 19:00Dr. Mark Hyman?

  and is not a substitute for professional care by a doctor or other qualified medical professional. This podcast is provided with the understanding that it does not constitute medical or other professional advice or services. If you're looking for help in your journey, please seek out a qualified medical practitioner. And if you're looking for a functional medicine practitioner, visit my clinic, the Ultra Wellness Center at ultrawellnesscenter.com and request to become a patient. It's important to have someone in your corner who is a trained, licensed healthcare practitioner and can help you make changes, especially Especially when it comes to your health. This podcast is free as part of my mission to bring practical ways of improving health to the public. So I'd like to express gratitude to sponsors that made today's podcast possible. Thanks so much again for listening.

• 19:43Dr. Mark Hyman?

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