in: Fitness, Health & Fitness, Podcast

• Last updated: September 28, 2021

Podcast #207: Primal Endurance — How to Become a Fat-Burning Beast

Are you an endurance athlete unhappy with your stalled performance? Are you constantly battling aches and pains? Are you running 30 or 40 miles a week, but still can’t get rid of the spare tire around your mid-section?

If so, this episode of the AoM Podcast is for you.

Today on the show I talk to Mark Sisson about his latest book Primal Endurance. We discuss the well-entrenched endurance training myths that many athletes follow that result in sub-par performance, and the counter-intuitive programming and dieting protocols you need to follow to break through your performance wall.

Show Highlights

  • Mark’s career as a distance runner and how it ruined his body
  • The difference between fitness and health
  • Why the typical methods of endurance training wreak havoc on the body
  • Why many endurance athletes who do tons of training are still overweight
  • The common myths of endurance training
  • Why you become a more efficient runner by running slow and not carbo-loading
  • The difference between aerobic and anaerobic activity (and why most endurance athletes are probably training anaerobically)
  • The heartrate you need to work at in order to stay in a fat-burning, aerobic state
  • Why barbell training is an important part of an endurance athlete’s training regimen
  • The role of sprinting in endurance training
  • The deleterious effects sugar has on the body
  • Adopting a fat adaptive diet to become a “fat-burning beast”
  • Lifestyle changes to make to improve your endurance performance

Resources/Studies/People Mentioned in Podcast

Primal Endurance book cover Mark Sisson and Brad Kearns.

If you’re an endurance athlete, I highly recommend picking up a copy of Primal EnduranceMany of your assumptions about endurance training will be challenged, but it doesn’t hurt to experiment with different ideas.

Connect With Mark

Mark’s Daily Apple

Mark Sisson on Twitter

Mark Sisson on Facebook

Mark Sisson on YouTube

Tell Mark “Thanks!” for being on the podcast.

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Read the Transcript

Brett McKay: Brett McKay here. Welcome to another edition of The Art of Manliness podcast. You’ve probably heard of the paleo diet, primal living, et cetera. It’s got a whole bunch of different types of names. One of the driving forces behind this movement is a guy named Mark Sisson. He’s got a website called Mark’s Daily Apple. If you haven’t been there, go check it out. It’s got a lot of great content on fitness and just health in general. Mark’s got a great new book out called Primal Endurance. If you’re an endurance athlete, if you’re in marathons, triathlons, do obstacle course races, this episode is for you.

Today on the show Mark and I are going to discuss some of the myths about training for endurance events, some of those being you don’t need a carb load, have the big bowl of pasta the night before your event. In fact, that can actually hurt your progress and your performance. We’ll also discuss how you’re training for endurance events and how you probably shouldn’t train as hard as you are training. In fact, you’re going to have to run slower than you think you should run, and sometimes you may even have to walk.

Today on the show Mark is going to explain why that is and give specific ways, examples, protocols on how to train, how to eat, what to do for recovery so you can perform your best. Not only perform your best, but enjoy your endurance sport for as long as you can. Great show. Make sure you check out the show notes after the podcast is over at, where you find links to resources and things we mentioned throughout the show. Mark Sisson, welcome back to the show.

Mark Sisson: Thanks Brett.

Brett McKay: Back after how many years.

Mark Sisson: Since 2009. That’s a long time pal. We’ve been growing.

Brett McKay: You have. You’ve grown phenomenally since then. The last time we talked, your blog, Mark’s Daily Apple, had just gotten started, all about primal living. You’re out with a new book for endurance athletes, for people who do triathlons, marathons, long-distance bicycling, those crazy people who do the ultra marathons. It’s called Primal Endurance.

Mark Sisson: And the latest one, obstacle racing.

Brett McKay: Obstacle racing. I’m a big fan of the obstacle racing. I don’t like just running. I like having my running interrupted with pegboards and the like.

Mark Sisson: If that had existed forty years ago when I started competing at an elite level, that would have been my sport I guess. Anyway, here we are.

Brett McKay: Here you are. Primal Endurance, this is interesting because you’re going back to your roots with this book. You started off your athletic career as an endurance athlete. For folks who aren’t familiar with that, tell us about your background as an endurance athlete. What did you do?

Mark Sisson: I was a distance runner, primarily a marathoner. I started out of necessity. I grew up in a small fishing village in Maine. I had to hike or walk or run two miles each way to school and just figured that running would get me home faster, so I started running at eleven, twelve, thirteen years old and joined the high school track team. Wound up doing pretty well in the mile and the two mile events. Rolled that over into college, where I was captain of the cross country team. Started doing road races in the summer. I got out of college, was good enough at running that I thought I would train for the 1980 Olympic trials, so I spent the next several years focused on running, putting in a hundred miles a week for many years. I got to be pretty good. I finished fifth in the US National Championships in 1980.

Yeah, I was down this path of human performance, but ironically I started down that path with an eye toward improving my health and longevity. As I got further and further down that path and became fitter and fitter and able to run faster and compete at a higher level, I found that my health was suffering. That was a little bit of a disconnect, because I had assumed all along that the more you ran the healthier you became and the better your heart was and the stronger your joints were and so on and so forth, but that wasn’t the case. At the end of around 1980 I was forced to retire from marathoning. I had osteoarthritis. I had tendinitis. I had all sorts of injuries that had piled up and I was getting sick a lot. I had irritable bowel syndrome and I was just a wreck really. I retired from that high level competition and devoted myself to figuring out ways in which I could be fit and healthy at the same time.

That’s what I’ve spent the last thirty-six years investigating and doing. Ultimately I came to this point about four years ago where I realized there is this convergence of technology now where we find that we can create the ultimate sort of high performance athlete and not sacrifice health, and that became the impetus for my new book, Primal Endurance.

Brett McKay: Okay. What’s interesting is that Primal Endurance, it shows athletes how to, like you said, be the optimal athlete, but it breaks or shatters a lot of myths. It goes against the grain from what you’ve heard if you grew up in the eighties and nineties about what you need to do to be an endurance athlete. I think it’s interesting too, you said you had these … You were fit. You could run long distances quickly, but you felt terrible. This is something that’s common in the endurance world, or was common. It’s becoming less common now. What is it about endurance training, the way people typically do it, that makes them feel terrible?

Mark Sisson: First of all, it’s like a badge of courage to tell somebody you’re a marathoner or an Iron Man triathlete or some ultra runner, that people go, “Oh, my God, what discipline you must have and what strength you must have.” That’s pretty much true, because most the time you’re out there you are managing pain. You’re struggling through these workouts and you’re going to the well in these races, digging as deep as you can. I don’t know of anyone who’s an elite level racer who ever says, “Oh, I was having so much fun out there.” Yet you talk to elite basketball players, elite football players, elite soccer players, they’ll tell you what a blast they were having on the pitch.

With endurance athletes it’s more of this stoic kind of management of pain. It was an assumption that we all had that in order to race fast you had to A, train fast, B, you had to practice suffering. The mindset was if I didn’t suffer today in my workout, the workout was not worth doing. For decades we went out and we put all these miles in and we ran literally as many miles as we could at the highest possible level we could, with the heart pounding as high as we could sustain and with the joints being able to maybe keep pace without getting injured. It was really what’s the highest amount of pain threshold I can create for myself in my training and sort of practice that on a daily basis so when I get into a race I’ll be able to recreate all this pain management and manage it in a better way. That’s foolish to think that that’s how we train.

Ironically, we also sort of understood through conventional wisdom that the way to fuel all this activity was to take in lots of carbohydrates. The understanding was when you manage your carbohydrate intake and you manage your glycogen stores, that’s how you become an elite racer, that’s how you become better at racing at whatever level you’re at, so that sort of begat this whole concept of carbo-loading. All of the gel packs and all of the drinks, the pre-race drinks, the during race drinks, and all that stuff was basically contemplated to get more and more sugar into your system so that you could burn more glucose and put off hitting the wall for long as you could.

Those two things, the intense mileage and the focus on carbohydrates, and particularly on sugar, kind of overlooked the main focus of what we should be looking at with endurance training, which is how do I manage glycogen by burning fat really well? How do I become more efficient at burning fat so that I don’t have to put in a lot of carbohydrate, that I don’t have to put in a lot of sugar?

Once you realize that fat is the preferred fuel for humans in general and that it becomes the preferred fuel for humans who are competing … Once you understand this, you can then begin to take on a training program that reconfigures your fuel partitioning, so that you get most of your energy from fat at reasonably high levels of output, that you spare glycogen, that you don’t put so much of this inflammatory carbohydrate and sugar and grain stuff through your digestive tract and your body, and, lo and behold, you become a more efficient runner because you’re burning fat at a higher rate, and you become a less injured runner because you’re not getting that chronic inflammation that consistently goes with the training, and because you can do so on slower training, and we’ll get to that in a little bit … It turns out that we were training at way too high a heart rate and too fast a pace to become efficient.

The only way you become efficient at endurance training is to manage your heart rate in a completely aerobic zone, which means at a much more comfortable pace. Now all these things come together. Now you actually become a better racer by training slower, strategically of course, by adapting your diet so that you become better at burning fat. When you become better at burning fat you burn off your stored body fat, so now we get to the point where you’ve got an ideal body composition. So many runners that I see at the beginning of a marathon … Seriously, you’ve got twenty-five or thirty pounds to lose and you’re entering this marathon and you tell me you’re training thirty, forty, fifty miles a week, how come you’re not losing the weight? That’s because they haven’t become good at burning fat.

We’re training at a much kinder, gentler pace, we’re eating the sorts of foods that encourage us to burn off fats, we’re getting injured less often and sick less often because of this reduction in inflammation. It all comes together to make for a strong, lean, fit, happy, healthy, productive athlete.

Brett McKay: Yeah, there’s a lot to impact there. I thought that was interesting, that statistic. I’ve read that other places, where they did a survey and they found that thirty percent of all marathon participants, they’re overweight, which is-

Mark Sisson: Isn’t that crazy? These are like marathon, they can run twenty-six miles, they’re probably the fittest people in the world, but a lot of them are overweight. By the way, they’re overweight because they’re stuck in this carbohydrate paradigm. Here’s how it plays out. You train really hard, but because you’re not burning fat at a high level, you’re still burning through all of our glycogen every workout you do, you get home, the brain says we just depleted all the glycogen. We better build back our glycogen source. We better eat all the carbohydrate we can get our hands on, so you carbo-load that night.

Then the next day you go I carbo-loaded, I better go out and train again, train hard. It’s this vicious cycle. The brain is telling you to overcompensate by replenishing the carbohydrates after a fashion and it gets to the point where every excess carb you take in raises insulin and is presumptively going toward fat stores once the glycogen stores are filled. You have this vicious cycle where you think wait a minute, I just sweated off five hundred calories today and every day for the last year and a half. You’re telling me I haven’t lost any weight? What’s wrong with this picture? What’s wrong with this picture is you haven’t become good at burning fat.

Brett McKay: Yeah. That’s the chronic cardio that you talked about in the book?

Mark Sisson: Exactly. Exactly.

Brett McKay: Let’s get into this difference, so the difference between aerobic and anaerobic training. I think most people think running, bicycling, those are aerobic activities. They think of lifting weights as an anaerobic activity. What you argue in the book is that many endurance athletes who think they’re training aerobically are actually training anaerobically.

Mark Sisson: Right. We’re always doing a mix of aerobic and anaerobic energy production. At the very lowest levels it’s ninety-nine percent aerobic, using oxygen to burn fat. Walking around the house, easy jogging, easy swimming, whatever, when your heart rate is just creeping up there, you’re in a most aerobic zone. As you start to increase the speed, the pace, as you start to increase the workload, as the heart starts to beat harder, you enter a little bit more of an anaerobic contribution, and that is the burning of glycogen through a process known as glycolysis. There’s a little bit of fat burning and then some glucose, glycogen burning. As you increase the pace and increase the rate of heart rate, it becomes less aerobic and more anaerobic. The anaerobic part is what we see when we start to build up lactic acid and we start to get out of breath because we can’t keep up aerobically, we can’t bring in oxygen enough to just do this with an aerobic oxygen based level.

Where we see so much happening with endurance athletes is because they can train at a high heart rate they choose to do so, thinking that the higher a heart rate that I can maintain in my training for an hour or an hour and a half, whatever, the better that must be for me. What it’s doing is it’s reinforcing this anaerobic type of training, which is that type of training which puts you into that lactic acid buildup phase that takes you away from the aerobic training.

The first lesson we learn in Primal Endurance is where’s that sweet spot where I can train my heart at its highest possible rate but still mostly aerobic? It turns out that it’s a number that’s proven empirically over the last twenty years to be one eighty minus your age, plus or minus a few beats based on genetics and pre-dispositions and perhaps your athletic history, but one eighty minus your age. In my case, I’m sixty-two. One eighty minus sixty-two is one eighteen, so one eighteen is the highest heart rate that I should be holding in long endurance efforts. If I’m on the bike, if I’m hiking, if I’m jogging, if I’m wandering around the house quickly or whatever I’m doing, one eighteen is that heart rate for me at which I’m putting mostly oxygen through my body and I’m not entering into an anaerobic contribution.

What a lot of people find is because they’ve trained so hard for so long … I could if I wanted to, Brett, I could go hold a hundred and sixty-five beats a minute on the bike for twenty minutes or thirty minutes, or maybe longer, but it’s not efficient. At that rate I am not burning mostly fat. I’m burning mostly carbohydrate and I’m reinforcing that whole energy system of carbohydrate dependency and I’m not becoming more efficient at burning fat. With that one eighty minus your age, which in my case is a hundred and eighteen beats a minute, that’s the maximum heart rate that I can go at.

People say, “Mark, I tried your program and I can usually run seven thirty miles, but when I limited my heart rate, I wore a heart monitor and I didn’t let my heart get above one forty for a forty year old, I was going like thirteen minute miles. What’s up with that? I can go a lot faster than that.” What’s up with that, we just proved that you are not very good at burning fat. We just proved that you are not very aerobically efficient. In Primal Endurance, in the book, we talk about one of the strategies for becoming more aerobically efficient is to limit your heart rate to that number for most of your base training. Don’t exceed it. If you do, not for very long. Over time, you’ll find that your efficiency improves.

That same person who was running twelve or thirteen minute miles over time is going, “Wait a minute. Now at my one forty maximum heart rate I’m doing ten minute miles,” or, “I’m doing nine thirties.” A month later, “Wow, I’m doing eight thirties.” What does that mean? What that means is that they’re doing eight minute and thirty second miles burning mostly fat, burning ninety-seven, ninety-eight percent fat, so that when they go ramp up the next phase of their training to become faster and more powerful, if you will, they’re starting at a much higher base of fat burning, which will benefit them when they get in a hard workout or they get a race against somebody who’s not as efficient as they are. Does that make sense?

Brett McKay: That makes sense. You got to slow down to speed up in the long run.

Mark Sisson: That’s the mantra. It’s counterintuitive at first, but when you understand the bio-mechanics and the bio-chemistry of it, you can see that if we’re talking about becoming a more efficient fat burner and we understand that fat is this preferred fuel that we want to tap into so that we can better manage our glycogen stores and spare glycogen, because there is this science that suggests that once the muscles are out of glycogen you hit the wall … If I’m running at the same pace as the competitor next to me and at the pace that we’re at I’m getting eighty percent of my energy from fat and twenty percent from glycogen and that person is getting forty percent of his energy from fat and sixty percent from glycogen, at the same pace who’s going to run out of glycogen faster? He is. If we go the same pace, he’ll hit the wall before I do. Conversely, if I want to match his fuel partitioning and I want to go forty percent fat and sixty percent glycogen, I’m going to be going a lot faster than he is from the get go because I’m that much more efficient.

Brett McKay: I imagine when people hear this and they put it into practice at first it’s extremely frustrating? You might be doing a lot of walking during=

Mark Sisson: If you’re a runner, yes. Or, as we say on the bike, you might be doing some paperboy up the hill. That’s zigzagging back and forth across the street with a bike full of papers back in the old days. I don’t know if that means anything to your audience, but it’s a cool visual for those of us who are over fifty. Basically I’ve had so many people report back to me exactly that, “Wow, I was so frustrated when I first started doing this. I wasn’t going that fast. I didn’t feel like I was doing much, but after a month of doing this I’m racing faster than ever and I’m not even doing any speed work. What’s up with that?” What’s up with that is you’re more efficient, you’re burning more fat so that when you do get to the high end you’ve got more glycogen to spare than the guy sitting right next to you who hasn’t been training that way.

Brett McKay: This is fascinating. Before we get into the nutrition, because that’s connected to this, let’s continue with the training. One of the other things you talk about in Primal Endurance that sort of goes against the grain of what you traditionally hear in endurance sports is strength training should be an important part of an endurance athlete’s programming. I think most people when they think of endurance athletes doing strength training, they think maybe some dumbbells, some lunges, but you’re recommending like barbell training, like dead lifts and squats.

Mark Sisson: Right. If you’re a runner or cyclist, it would be the lower body stuff, the complex exercises like weighted squats and dead lifts. The reason is it’s to develop sustained power. What happens in a race … A couple things happen when you’re competing, one of which is certainly that ability to produce energy at a more efficient rate and to feel the muscles, but the muscles still have to have the ability to withstand the demands of increased output, whether it’s sprinting, whether it’s climbing hills as a runner or climbing hills as a cyclist.

What we see happening over time, particularly in the longer events, is that athletes may have a hundred percent of their max power on the first hill, but then the second hill rolls around and even though their energy production is reasonably good, the muscle fibers themselves are starting to cap out because they haven’t trained for this ability to sustain power over time. We see cyclists who will maybe climb the second hill at seventy-five or eighty percent of their max capacity or max power, and then by the time the third hill rolls around they’re at sixty-five percent.

What can we do in terms of training to increase that ability to sustain power over the long haul? What we do is we load those muscle fibers deeper and deeper. We put more stress on them in a short period of time through specific things that we do in the gym. For example, we might do weighted squats and we might determine what is my one rep max on a squat? Let’s just say if you’re an endurance athlete it might be two hundred pounds. Then we take eighty percent of your one rep max, we call that one sixty, and instead of doing one rep and stopping, or conversely instead of doing eighty or hundred pounds twenty or thirty times, ten reps times three stats and then walk away, we take a hybrid of that and we go eighty percent of your one rep max, we’ll do as many as we can right now, do a quick ten second rest, don’t even re-rack the equipment or don’t really walk away from it, do it a couple more, maybe take a short rest there, do a couple more.

We keep loading those fibers until we can’t complete one more rep with perfect form, form being sort of the main arbitor here. What we’re doing is we’re loading the fibers and then we’re backing off a little bit, and then we’re loading them again and backing off a little bit, but we’re loading them maximally. We are recruiting fibers deeper and deeper into that muscle tissue to the extent that those fibers become able to handle the power demands that may be called upon in a sprint halfway into a bike race or a hill climb, a charge up the hill, or Heartbreak Hill at the Boston Marathon or something like that.

Basically we’re training the component parts of what a race consists of, but doing so in a way that rather than just practicing doing them we are breaking them down. We’re parsing the entire goal into its component parts so that we’re dealing with the aerobic efficiency, we’re dealing with maximum sustained power. We’ll talk later about sprinting and how we look at sprints as a form of interval training. Then ultimately we’ll look at how the diet is important in reconfiguring how we extract fat from our stored body fat.

Brett McKay: How do endurance athletes avoid the risk of bulking while doing strength training? On cyclists and runners, every little bit … Sure you have more muscle and that muscle can do more work, but that’s like more weight you have to carry around. How do you address-

Mark Sisson: First of all, if we’re doing lower body training in the gym, you’re not bulking up on top so you’re not really carrying around any extra weight on top. We’re not having you do biceps curls and lad pull downs and deltoid raises an things like that. You can if you want to, but that’s not the point here. The point here is how specific can I get in the gym in the weight training so that I’m building power and not putting on useless mass around my entire body. When we’re talking about doing weighted squats or dead lifts, we’re just talking about leg muscles. You will not bulk up. It’s just impossible, because if you’re doing the work running you’re still going to be leaning out that muscle tissue. It’s just that what we’ve done is we’ve worked on your power. We haven’t worked on your size, we’ve worked on your power.

Bulking up is not an issue. I defy you to show me one cyclist who has complained about bulking up because of the work he did in the gym. Most cyclists, you look at their quads … Even if they’re not doing gym work, their quads are pretty big meat slabs, especially the sprinters, because of that work that they do. Nothing you do in the gym is going to hamper or hinder your ability to race efficiently. It’s really about the power to weight ratio that we’re developing. Cyclists in particular, they look at this magic number of six watts per kilogram. If you can get to six watts per kilogram over extended periods of time you’re going to beat the guy next to you, given the same equipment and everything else.

Brett McKay: Let’s talk about sprinting, because that is an anaerobic activity. How does this fit in with the idea that we want to build an aerobic base in our endurance training?

Mark Sisson: Sprinting comes in because a couple of reasons. Number one, sprinting is another way to work on that sustained power, that deep power. When we talk about sprinting, we’re not so much talking about the old school of the intervals. If you’re a marathoner, you probably did a lot of half mile repeats or mile repeats or really longer intervals that we really wouldn’t call sprinting to begin with. It was rare, at least when I was training, that a marathoner would do hundred meter sprints or two hundred meter sprints. It was like that doesn’t apply to what I’m doing in the marathon. I’m never running that fast, so why should I train that fast? The answer is because what we’re training, first of all we’re looking at how can we get the most effective workout with the least amount of pain, suffering and sacrifice. We call it the MED, the minimum effective dose.

When you’re sprinting, if I can show you that by doing six to eight sets of ten to twenty second sprints all out after a warm up … Obviously you want to warm up, but all out, maximum effort and then you’re done, you might go, “You’re crazy, Mark. How does that help me with a 10K or a marathon?” What it does is it works those completely anaerobically, which has it’s on metabolic side effects that create the gene expression that builds power and strength and speed, but also it’s working at the level of the structure of the tendons, the ligaments and the muscles. You’re doing a lot of work in a very focused period of time that allows you to spend shall we say less time on the ground and more time in the air if you’re a runner, or more efficient at pedaling through the entire barrel of the stroke. If you’re a cyclist, then you know what I’m talking about.

The idea to become an efficient cyclist is to be inside this cylinder that you’re always trying to pedal out of, so you’re pushing forward in the front, you’re pushing down on the downstroke and you’re pushing back on the backstroke. You’re not just hoping the pedals get over the top and then stomping on them, but you’re becoming more efficient. All of these things, whether you’re sprinting as a runner or as a cyclist, and it works for swimming as well, that sort of training is now preparing you for that efficiency of the actual work being done by the muscle itself, so not so much in terms of the energy source, but in terms of the mechanical force that’s being produced by that set of tendons and muscles. Does that make sense?

Brett McKay: Yeah, that makes sense. In the book people can find out how all this training works together. You lay out a suggested program in the book. What I love about your book as well is that you give prescriptions, but it’s not overly prescriptions. I think the overarching theme or idea in the book is you’ve got to just listen to your body, do what works for you.

Mark Sisson: My goal here is to make people intuitive about their training. How I elected to do that is through some education, this is how the body works, this is what we’ve learned from the science in the past twenty years that we didn’t know twenty or thirty years ago, here’s how we can apply it if we want to. Ultimately, you are the best coach for yourself. When you understand the ramifications of these choices you’re making and you wake up in the morning and you say how do I feel today? I had this planned, but if I don’t feel like doing it I’m okay taking the day off. I don’t have to feel guilty because I was supposed to go for an easy fifteen mile hike today or an easy fifty mile bike ride or whatever, but I don’t feel like it and I don’t feel prepared, then great. Now you’ve become intuitive.

Wait until you’re ready for it, and particularly true with a sprint day for instance. If you’re not firing on all cylinders on a sprint day, don’t do it. You’ll gain more by taking the day off and resting than you will from slogging through a workout that may predispose you to injury or may set you back because your immune system wasn’t ready for you to dig that deep that day.

Brett McKay: Okay. Let’s go back to nutrition, because this ties in tightly with the training. The goal with Primal Endurance is you want to focus on aerobic training, and that requires fat. It burns fat as fuel, so I imagine the diet we want when we’re training on the Primal Endurance way is more fat focused as opposed to carb focused?

Mark Sisson: Yeah. Correct. It’s more healthy fat focused for sure. We look at what are we trying to do here. We’re trying to force the body to make changes, to up-regulate gene systems that will build a more powerful set of muscles, that will allow us to be able to access stored body fat and burn it more efficiently. That means building more mitochondria, which is where the fats burn within the cells, making those mitochondria more efficient. All of this happens as a result of genes turning on or off in response to the signals we give them

Brett McKay: This is epigenetics?

Mark Sisson: This is epigenetics. This is the key to everything we talk about in primal blueprint, in primal endurance, in everything primal, paleo, ancestral. How do we harness the power of our genes through the epigenetic choices we make, with the foods we eat, the types of workouts we choose to do, with the amount of sun we get, the amount of sleep we get, the amount of play we take on? One of the strongest sets of epigenetic regulators is food. The very fact that we could eliminate or cut way back on carbs is a powerful signal to the body that wait a minute, I’ve been relying on carbohydrates my whole life because you’ve been feeding me every two or three hours, and now you change. Now you’re cutting back on the carbs, you’re not feeding me as often, you’re feeding me more fat. I guess I have to adapt, so the body up-regulates these enzyme systems that are involved in taking fat out of storage.

It up-regulates those enzyme systems that are involved in building more mitochondria. The mitochondria have their own DNA. Those mitochondria respond by getting more efficient at burning fat, and lo and behold, over time, by having reduced the sugars and the simple carbohydrates in your diet, by having increased the amount of health fats and pretty much kept protein steady, you have I say reprogrammed your genes to become a fat burning beast, to make you a fat burning beast, to make you able to access stored body fat on a minute-to-minute basis so that you don’t have to rely on carbohydrate at every meal. You don’t even have to rely on three meals a day.

Most people who are in this space right now are doing some form of compressed eating window, where they wake up in the morning, they’re not really that hungry because they’re so good at burning fat, they’re literally not having fasted overnight because the body has been taking its energy from stored body fat, so you wake up, you’re not hungry, and I say if you’re not hungry why do you want to eat? You’re good at burning fat, become more efficient at burning fat.

A lot of these people who are doing this type of training don’t eat until noon or 1:00. It’s what we call a compressed eating window or intermittent fasting. They have their first meal at 1:00 and then they have their last meal of the day at 7:00pm and it starts that cycle all over again. In between, in those eighteen hours in between, they’re burning a lot of fat and they’re training their body to burn fat, and that translates directly to how they access fat when they go out and do that aerobic threshold training. It’s a beautiful sort of reinforcement synchronistic system.

Brett McKay: I love the analogy you made about the book between carbs and fat with the power plant. Carbs are coal. It’s dirty. It can get the job done, but not very efficient, not very clean, whereas fat is more like solar power.

Mark Sisson: Exactly. Solar power is unlimited and fats are virtually unlimited. I think back to the original premise that we opened this discussion with, which is that for the longest time we thought that what determined your success in a race was how you managed glycogen, but when you realize that the body can only hold about two thousand calories worth of glycogen at any one time and of those two thousand calories, four hundred sort of reserved in the liver for the brain, and that leaves sixteen hundred. The muscles will never willingly run out of glycogen completely down to zero, so maybe you’ve got twelve hundred calories accessible for this race that you’re going to do. That’s three hundred grams total of carbohydrate.

Your body you can store … Even on a lean athlete you can store thirty or forty thousand calories worth of fat, and in some cases more. That’s enough to jog easily three hundred miles. A big difference there between these two sources of energy. Back to the more you can become efficient at burning fat, the more you can reduce your reliance on carbohydrates and this glycogen reserve that you have, the better you will compete, the less sugar you’ll put through your system … We didn’t even talk about the sort of devastating effects of a lifetime of consuming high amounts of sugar.

Brett McKay: It’s terrible. It’s fascinating what sugar does to our bodies.

Mark Sisson: Yeah. It’s clear that of the thirty-five million people that are either currently diagnosed or will be diagnosed with type two diabetes in this country, it’s that inability to manage large amounts of glucose coming into the body, whether it’s from sugar or whether it’s from even sometimes “healthy” sources of carbohydrates like grains and whole grains, refined grains and things like that. The excess sugar is very toxic to the body. The body has a lot of ways of getting rid of excess sugar, which is another kind of red flag, when people say wait a minute, glucose is the preferred fuel of the body. It it were so, why would the body have all these mechanisms to limit the total amount in our bloodstream to what amounts to a teaspoonful at any point in time? Why would it allow us to store unlimited amounts of this other very efficient fuel that we call fat?

Too much sugar is inflammatory. That was one of my biggest issues with my heyday of my training, when I was consuming seven hundred to a thousand grams of carbs a day to be able to fuel my hundred miles a week of training. It turns out that that was very pro-inflammatory, just the pure sugar that was in the drinks and the sweet stuff that I was taking in, but also in the form of the grains that I was consuming. I found in my case that I had a big issue with gluten and gluten analogues that exist in other grains to the extent that when I eliminated all the grains from my diet the major source of inflammation throughout my body went away, and that was life changing. The arthritis that I had in my feet for thirty years, that went away. The arthritis that I just recently started to develop in my early forties in my fingers went away. I thought how could that possibly be? That’s just normal arthritis, isn’t it? No. It was completely related to the foods that I was eating.

When you see the immediate effects of reduction in pain from inflammation … I mean my IBS went away. That was a huge thing for me. All these pain elements in my body went away that were largely determined by inflammation. I started to think in terms of the latest philosophy in heart disease, which is that heart disease is not a factor of cholesterol and saturated fat per se, but it’s a disease of inflammation and it’s really the cholesterol that’s acting as a band-aid within the blood vessels that’s caused by the inflammation that becomes the issue. If you don’t have the inflammation, then you don’t have the issue. I started to think maybe all of the stuff that was obvious to me from the inflammation in my fingers, the arthritis, the IBS, maybe I just dodged the bullet here, because that same inflammation was happening in my arteries and now I can visualize that it’s not happening at all because I removed those inflammatory offending ingredients.

Brett McKay: You’re right. I remember it was like during the eighties and nineties, the whole cholesterol and fat is bad is for you. That’s when the whole low fat foods came out. There were Snackwell cakes, fat free margarine, and now we have research coming out, even the health organization with the government is saying yeah, what we said twenty years ago, you can ignore that.

Mark Sisson: I wish they’d say that, but they don’t quite say that. They say maybe some of the research on saturated fat isn’t as overwhelmingly negative as we’ve been telling you for forty years, so they’re slowly backtracking, but it’s still frustrating to see that the guidelines, at least by the US Department of Agriculture and the FDA and the Departments of Health, that are clinging to this notion that we should still limit fats to a very low number and we should still make complex carbohydrates the base of our food pyramid.

Brett McKay: Yeah, it’s frustrating. To sum up, nutrition, primarily you want to go fats. We’re talking about good fats here. We’re not talking pounding back State Fair corn dogs and waffles. We’re talking like avocados, olive oil-

Mark Sisson: State Fair corn dogs, I like that. Exactly. We’re eliminating the industrial seed oils. We’re getting rid of soybean, corn oil, canola for sure, and all of these industrial seed oils that have been permeating our food supply for the last forty years. When you buy a processed food, which I hope you don’t, check the packaging and if it has any of those offending oils don’t buy it, but absolutely take in avocado oil, coconut oil, butter, ghee, lard-

Brett McKay: Nuts and butter fats.

Mark Sisson: Things like that, and then grass fed animals if you’re inclined to get your sources of protein from animals, either pastured chicken, grass fed beef, line caught wild salmon and things like that.

Brett McKay: Your carbs should probably be like vegetables? We’re talking like broccoli, sweet potatoes. You do talk about in the book you could go no carb and go to a ketosis, which is even cleaner than fat, but you don’t have to do that.

Mark Sisson: Right. You don’t have to. That’s sort of the next level stuff that we talk about, the ketosis. I’m giving a talk in a couple weeks on ketosis and how as an athlete you can use ketosis to your advantage, but it’s a commitment, and I’m not even spending that much time in ketosis, even though I’m a big fan of it as a tool for enhancing your ability to burn fat. I’m a fan of cyclic ketogenesis, which means you go into ketosis for a couple of days or a week, then you go out for a while. When you’re in ketosis, you’re giving your body those signals, which is improving the efficiency of mitochondria, it’s doing a lot of good things. Then when you go out of ketosis, as long as you don’t start cramming down sugar and increasing your carbs dramatically, you’ll retain that metabolic machinery that you just built. There’s a way to, I was going to say have your cake and eat it too, but I wouldn’t say that.

Brett McKay: Have your olive oil and-

Mark Sisson: Yeah. Have your cheesecake or whatever … Not cheesecake, whatever. There’s a way to do this and get the benefits of all the tools and strategies that we talked about here. You don’t have to really commit to being in ketosis for a long period of time or for the rest of your life, as some people I’m talking to … They’re so enamored of it that they’re saying this is the way to a really long life. To be honest with you, I just like to eat such a wide variety of foods that I don’t want to eliminate so much from my diet that my gustatory pleasure is compensated for.

Brett McKay: Besides the diet and the nutrition, what other lifestyle changes should endurance athletes make to perform better?

Mark Sisson: A lot of stuff we talk about in the book is find ways to move throughout the day. Every time you’re moving throughout the day you’re contributing to your aerobic efficiency. If it’s a stand-up desk … At my office, all my employees have the option to get a treadmill at their stand-up desk if they want. Some people are putting eight or nine miles a day of easy walking while they’re doing their work. Find ways to move. Take a lunch break with your workmates, have a meeting during a walking session. That’s sort of the new thing among the we work crowd and the millennials, is having walking meetings.

I get a massage once a week. I’m a big fan of deep tissue massage, so I get worked on, get the kinks worked out, get sort of actively stretched, or passively stretched I should say in that process. I like cold therapy, so I do a little cryotherapy. I have an unheated pool. Every night before I go to bed I might jump in the pool, spend two or three minutes cooling down, and then paddle off and go to bed and I sleep like a baby. Sleep is another important part of our ability to perform better. We only perform well when we recover and improve from our workouts, and sleep is that time at which the body is doing its greatest amount of restoration and repairs, so it’s critical that anybody intent on improving performance manages sleep to the extent that they’re getting seven and half to eight hours minimum per night.

Brett McKay: Mark, this has been a fascinating discussion. Where can people learn more about Primal Endurance and the rest of your work?

Mark Sisson: Mark’s Daily Apple is my blog. I’ve written a post every day for going on ten years now. is our eCommerce site where you can buy our books, get the Endurance book there. Also some of our healthy fats, we’ve got a new line of product called Primal Kitchen, so we have very health mayonnaise, the world’s healthiest mayonnaise made with avocado oil there. Those two sites, and you can obviously buy Primal Endurance on Amazon and finer bookstores anywhere. If you’re interested in becoming better at performance, whether you’re an athlete or not, it’s a cool new strategy and technology.

Brett McKay: Mark Sisson, thank you so much for your time. It’s been a pleasure.

Mark Sisson: My pleasure as well Brett. Thanks.

Brett McKay: My guest today was Mark Sisson. He is the author of the book Primal Endurance. You can find it on Also make sure to check out his website, He’s got tons and tons of free content out there about eating, primal living, exercise, et cetera. You name it, he’s got it. Go check it out. Also make to check out the show notes at

That wraps up another addition of The Art of Manliness podcast. For more manly tips and advice make sure to check out The Art of Manliness website at If you enjoyed this show, I’d appreciate it if you give us a review on iTunes or Stitcher or whatever it is you used to listen to the podcast. Also tell a friend about us. That would be one of the best complements you could give us. Appreciate your continued support. Until next time, this is Brett McKay telling you to stay manly.

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