Good morning, and welcome to the show, Dr. Fahre. We're so happy to have you. Thank you — really looking forward to this.
We read your book, *The Pulse Cure*, and loved it. Thank you for sharing your wisdom — it's quite interesting, and a lot of people probably don't know much about it, despite the fact that so many people have wearables and use them daily. I'm one of those — I've had a Garmin watch for a while, but I honestly haven't gotten into the weeds looking at the details of HRV specifically, so I'm really turned on to learning more.
What Sparked the Passion for HRV
What led you to become so passionate about HRV as a window into health? It was a bit of a coincidence. I was reading Bessel van der Kolk's *The Body Keeps the Score* and understood that HRV was such an important metric for the autonomic nervous system, which I'd already been interested in for years. When I understood you can actually measure it, it was like a lightning strike — "Is this really possible?" For a couple of years I used an ECG-based device, and then I realized we have this metric in Garmin watches, Oura rings, Whoop bands, and so many other devices, which made it actionable.
I was interested in improving my own physiology, and after a couple of years my publisher became aware of what I was doing and asked if it could be a book. In Norway it's been an extreme success — in US numbers that would be like 3 million copies. It's totally transformed my life from being an anonymous doctor having one-on-one conversations to being in the media all the time, so now I really have to pay attention to what my watch is telling me.
What Heart Rate Variability Is
For listeners who don't know, what is heart rate variability? HRV is the variation between heartbeats. As a doctor, I — and probably most people — would think a good heart rhythm is a very steady one. But that's only true if you're in the stressed state, which is good if you need to mobilize your forces and do something hard. If you're in that stress state all the time, you're overtaxing your physiology, wearing yourself out, and not allowing your body to recover.
When we're in the recovery, parasympathetic restful state, there's variation between heartbeats: when you breathe in, the heart rate speeds up a little as the lungs fill with oxygen, and when you breathe out it slows down — just milliseconds, but detectable, and you can feel it if you're really calm. So you can use your heart rate as a monitor for the intensity in your life. Having this on our wrist at all times, compared with millions of people using it, with AI and algorithms, makes it a powerful tool that can tell you whether you're living a lifestyle compatible with health and energy over time.
The more you look into it, the more it's related to just about every aspect of health, from mental health to chronic disease. Almost any disease you Google or put into AI is associated with low heart rate variability, because being too much in the stress mode won't allow your immune system to work properly — and then any disease in any organ can come through, from autoimmune diseases to heart disease and cancer.
Catching Problems Before You Feel Them
One thing you talk about in the book is that your HRV can show an issue before you feel it in your body. How? Often your immune system reacts to a urinary infection, pneumonia, COVID, or just about anything before you feel the symptoms, because the symptoms come once the immune system is fully powered on. Before that, you might see a day or two in advance that something's happening. HRV and respiratory rate are two of the things that noticeably change before we detect other changes.
From Reactive to Personalized
How are you using HRV to move from a reactive model to a more preventive, personalized approach? I use it to get to know my body better — to learn what strains it from surprising sources, and how much energy I have on a given day, because I try to use only the energy I've saved up. For example, I've just been to an intense three-day wedding in Barcelona, came back late last night, spent a lot of energy, and had some alcohol, which I do maybe three times a year because it's such a big stressor. So I know I'll need to recover — I can see clearly on my watch that my body is still working on that intense experience. It was worth it, but I can't just start the week with as much activity as usual. You get insight into how much energy you have to spend — should I train today, or make sure I get enough sleep or a power nap?
It's like having insight into what goes on under the hood of your car — the engine temperature, how much fuel is left, your speed. This is the same for your body. The reason it's become a bestseller translated into eight or nine languages is that it works: once you get your stress balance under control, you feel it — fewer symptoms and more energy — and then people tell everyone else. We see a lot of folks who don't realize how stressed they are until we show them numbers.
Comparing to Others vs. Your Own Trend
Should we compare our HRV to others, or to our own trend? Both, but mostly your own trends, because the devices use maybe three weeks of calibration to your system. There's a 30 to 50% genetic variation, so two people — one with 30 milliseconds and one with 60 — could have the same objective level of health. But if you have a really low HRV, chances are you can improve it more. It's important to keep both thoughts in mind, which speaks to why personalized health care is so important — everybody is different.
This is great for personalized medicine, because usually as doctors we get results from a study of thousands of people, and the number is the average, which doesn't tell you how *you* would respond to a medicine or circumstance. Here you can see how you react to alcohol or a workout — it depends on your system, and you'll respond differently to the same activity.
Hormones, the Menstrual Cycle, and Menopause
How do women's hormonal shifts with perimenopause affect HRV? When you get into perimenopause — a word we as doctors probably hadn't even heard five years ago — you see a decrease in HRV and become more vulnerable to stress. If you had a balanced life, you might not feel the same symptoms, so you have to take more care with your stress balance going into menopause. And you see that when you get the right hormone replacement, your HRV responds — many women tell me they feel better on bioidentical hormone replacement than synthetic versions.
Regarding the menstrual cycle, the week before the period is a substantial strain on the system that many women don't take into consideration. They think they're just feeling bad, irritated, or snappy, but we can see from HRV that it's a physiological load as large as a strong COVID infection — the same curves, similar in both depth and length (about a week). To have something as hard as a COVID infection for one week every four weeks is quite hard. But the magic is that if you start mitigating stress particularly in that week, you can flatten that curve and be relieved of many symptoms. So if a woman balances lifestyle changes, gets better sleep, reduces fatigue, and balances hormones, her HRV improves and she feels better.
The symptoms we see in perimenopause — sleep disruption, fatigue, mood swings — are also the things you address to improve HRV. The same strategies anyone uses for stress management — breath work, cold therapy, meditation, sunshine, adjusting your circadian rhythm — become particularly important during stressful times like the week before the period and menopause. It also means things you should *not* do or eat: alcohol and food you can't tolerate well. Many people are shocked how much food affects their stress levels — mostly ultra-processed food, sugar, and flour-based food like bread and bakery items. Personally, I find chili really stressful — I feel like I have a hangover the next day, and I can see stress levels throughout the night as high as if I'd given a lecture to 200 people.
Data vs. Intuition
How does using tools to monitor HRV differ from just being intuitive about our body? It would be great if we were that intuitive, but we're just not, for an evolutionary reason: throughout evolution, all threats came from the outside, so we have excellent eyesight, hearing, smell, and taste. What was dangerous was enemies, animals, a snake, or a fire — we never needed to worry about our inner stress levels, because as hunter-gatherers we were either hunting, gathering, and fighting, or relaxing by the bonfire and sleeping at night.
But stress is reflected in the heart rate. We can see millions of shades of color, but whether I have 60 or 80 heart rate right now, there's no way I could feel it — and that represents a huge difference in stress levels. As a doctor, I even used alcohol to wind down in the evening, thinking it was a stress reliever — it turns out it's the worst thing I can do. The body speaks softly, and we are poor listeners. If we were good listeners, we wouldn't have these problems with stress, fatigue, brain fog, and all the lifestyle diseases we struggle with.
HRV for Athletes and Training
As someone who does endurance events, what should I look for with HRV, and how does it affect performance and training? Often an athlete uses resting heart rate to measure their state, but HRV is much more sensitive — it's like watching your heart rate with a magnifying glass. I've seen an athlete who was overtrained whose resting heart rate only went from 41 to 43, but his HRV was 50% lower — from about 105 down to 60. He couldn't see the difference in heart rate, but the HRV made it obvious.
As an athlete, you put strain on your body and then recover to build yourself stronger. If you just strain your body without allowing recovery, you're wasting your energy and time. People who train and pay attention to HRV can train less or less intensely and become stronger or faster.
What trend indicates overtraining? On your Garmin, you'd probably see the four-week HRV trend go from the green zone into orange, or even red. In the green zone you're okay; if you become unbalanced you get an orange warning, and if it gets really low, the red triangles show you're moving in the wrong direction. Even as an athlete with better mitochondria and VO2 max, you could still be affected by chili, flour-based food, milk, or alcohol — things that take your energy and don't give anything back. So you'd still need to identify what's taxing you as a waste of energy, versus what you're truly investing, like a workout or a mental challenge.
Tools to Boost Your Battery
We've talked about what drains our energy. What tools boost our battery? Breath work is maybe the most important — to calm the system down so the parasympathetic recovery state and the vagus nerve can do their job. Breathe slowly with a longer exhale, multiple times a day, so it becomes a habit that when you get stressed, you breathe slower, not faster. Cold exposure is important — finishing your shower with cold water, or going to a lake — though a lot of athletes use cold to dampen inflammation after a workout, which can reduce the strength gains if strength is what you're after.
Sunlight is important. I'm currently writing a book on sun exposure, because the sun's energy goes straight into our mitochondria and cells, making them more efficient in energy and hormone production. We are living solar panels that have, for some curious reason, been advised to stay out of the sun — which just isn't true. Half of sunlight is infrared, so infrared saunas can be useful and you can see it in your HRV. The only thing that produces the opposite of that dip — the pre-period or COVID curve — is the sun. When Norwegians (Norway is about the same latitude as Alaska) go to southern Europe, Africa, or the Caribbean, their HRV can double, because the sun releases nitric oxide in the skin, improves circulation, produces vitamin D, and makes mitochondria work better. That's much of why there's more heart disease in the winter than summer. So the prescription is simply getting out in nature.
The Effect of Alcohol
You've talked about alcohol as one of the biggest impacts. Can you explain its effect on long-term health? Once you drink alcohol, it's calming — I can see on my watch that a couple of glasses of wine put me into a deep parasympathetic state. But in your body, alcohol is transformed into acetaldehyde, which is really toxic, and your body works hard to get rid of it. That's why, while I'm sleeping, the stress can be as high as if I were holding a lecture. People are shocked to see they've been working as hard as a full day of work during the night. According to Whoop, alcohol is the worst stressor of all, taking up to five days to recover from an evening out. I haven't met anyone tracking their system who hasn't reduced their alcohol. Over time, the people who drink a lot look the worst and have more disease and shorter lives — obviously a big contributor both day-to-day and to longevity.
Particularly as we get older — when we're young the body is forgiving, with mitochondria at full power — after 40 all our organs work more poorly. I often say that until you're 40, the body does the work for you, but after 40, you have to do the work for the body.
Adding 24 Years to Your Life
You cite a study about adding 24 years to your life. An American study of about 700,000 veterans, followed for 10 to 15 years, showed that when you compound the different lifestyle strategies, you can add 24 years to your life if you have them from age 40. The good thing is that if you start at 60, there's still around 18 years to gain — basically doubling the remaining part of your life. The eight strategies are: good nutrition, drinking less alcohol, not smoking, sleeping well, having a stress-management strategy, physical exercise, and good relationships and connection. When you can check off all of those, you live 24 years longer on average. As a doctor, I used to do all this advice wrong, because we thought there were maybe only five years to gain — so I thought, "It'd take me five years of effort to gain five years." Now we know the budget is quite different: with the effort you gain 24 years, not five.
Which is the biggest one? Physical exercise, and probably sleep, then nutrition and relationships — they're pretty similar on the graph, but those four are at the top. The most overlooked? Probably exercise and sleep. That's why *The Pulse Cure* starts with sleep — once you get good sleep, you have more energy to do the things that require more effort, and the body does sleep by itself; you just have to make it possible. What makes it possible: not eating maybe three or four hours before bed, dimming the lights or wearing blue-blocking glasses in the evening, keeping your bedroom totally dark and cool (around 60 to 65°F), and avoiding alcohol. Once sleep is right, it's easier to do the other things — and then I'd start with exercise.
If you're not used to exercising and have a low VO2 max, you don't tolerate much strain, so pay attention to the Garmin watch, which tells you how much recovery time you need after exercise. For people not used to exercise, I'd advise keeping that recovery time below 24 hours — because with a low VO2 max, a normal run could give you three or four days of recovery time, while someone with a good VO2 max would shower it off in half an hour. What's your VO2 max, Mark? In the 60s. That's crazy — you'd be in the top 0.1% of people. I stay very active, take care of the house, sleep well, eat right, and avoid alcohol. I take a lot of interest in recovery too — I don't run every day; I do different activities so I can rest, which makes a huge difference.
Choosing a Device
So the Garmin watch is your go-to? Yes — if you want to micromanage the things I'm talking about, Garmin is really the only choice. Whoop, Oura, and other devices are more crude — they don't give you the graph where you can pinpoint the exact 10 or 15 minutes that are stressful and to what degree. Garmin is more actionable with more data power. They're the best because they bought the Finnish company Firstbeat Analytics — the ECG-based algorithms I used for a couple of years. Polar H10 chest straps are also good; it's the software more than the hardware that matters most.
Is there an accessible level of Garmin? The cheapest one that's good enough is the Forerunner 165 — you could get it for a couple hundred dollars, or secondhand. Whoop and Oura would be about twice that price with a subscription. The battery life on a Garmin is impressive — mine lasts about 16 days, and I've had ones that lasted 30. Charging for an hour every 16 days is fine.
Turning Data Into Lasting Change
How do you encourage patients to translate HRV data into lasting behavior change? Use it as motivation — seeing the consequences when you do a good thing, like fasting, cold water, or staying off alcohol, is the most important. It's like economics: if you didn't know how much things cost or how much money you had, you'd be blind. When you get insight into the physiological price of your expenses and income, it becomes so much easier to change your lifestyle — which every doctor knows is the hardest thing for people. You also see the minor results you couldn't feel but can see on the watch. We have patients who feel they aren't improving, but when we show them their body composition and HRV, they see, "Yes, I am doing the right things," and it's a game-changer.
Do some people get too hung up on their numbers, making it a stressor? Some people get too hung up on things generally. This is just a reality check. It's like if your car dashboard lights are flashing — the engine's too hot — and you call the mechanic and he says, "Just take out the fuse so they won't disturb you." That's not a good option. People who get too hung up tend to be impatient and frustrated by things outside their control, and they need to be more accepting, understand that change takes time and smaller steps. It's not necessarily for everyone, though I believe it's for most. I wrote the book for the ones who think, "This gives me insight into my physiology — I want that." Funnily enough, from what I can find on Amazon, this is the only book giving you this information from a health standpoint, even though half the population uses an Apple Watch, Samsung, Garmin, or similar — so it's a surprise more doctors haven't written about it.
Getting Started
For someone who wants to start measuring their HRV and improving their lifestyle, what do you suggest? Look at the Garmin options, get the book *The Pulse Cure*, and read through it to understand what you'll be doing. In the first month, don't change anything, so you have a baseline — I'm very curious how my baseline looked all those years ago before I changed my life. Take it easy; the most important thing isn't how you are in three or six months, it's where you are one, two, five, or ten years from now.
You have other resources too? Yes — thepulsecure.com has more information and a blog, and the book is also an audiobook if people would rather listen. You can find it on Amazon and even in the book app on your iPhone.
A Life of Adventure
From reading the book, I know you're an adventurer, and we love adventures. What's a recent one you enjoyed? The recent one was sailing a month in the Caribbean from Grenada up the Grenadines with my family. We've sailed halfway around the world together. I like those not-extreme adventures — being out in the world and in nature, seeing how the world looks. I've traveled to maybe 85 countries, and now that my children are becoming adults, I look forward to traveling more. That's my motivation behind the health change — even as a doctor I wasn't really interested in health in itself, but it's something you need to live your life. It's not about spending every day trying to get better health, but having it as a basis for living your life.
Thank you so much for your time today, and we look forward to your next book. Thank you for having me — have a great day.