Mark Sisson on Achieving Metabolic Flexibility Through Fasting

You know, I've gone through, again, all these iterations of trying to assist people with the information that I've come across in my research on how they can achieve an ideal body composition, have more energy, maintain or build muscle, improve their immune systems, have better sex, be more productive, whatever it is. These are the things that these are what I'm trying to, the hidden genetic switches that I'm trying to uncover for people. In so doing, you can choose to do it or not. I'm not suggesting you have to do this to have a great life, but here are some of the ways that we do it. It started with a primal blueprint and then sort of morphed into, well, the primal blueprint works really well for a lot of people and even worked well for me, but is there something else? Is there a new level I could get to? That was the keto. I wrote a book called The Keto Reset Diet since I was on here. I was in the keto for a while, but then I sort of said, well, ketosis is not a way to live your life. It's a tool, a strategy that you can use to build metabolic flexibility. Some people do think that it's a way to live your life though. Dom D'Augustino, he does it all the time. Yeah. I mean, I have a lot of friends who do keto the whole time. I'm not a person who says, that's the way. Keto's the be all and the end all of how you should live your life because I'm more about achieving metabolic flexibility. That's a term that's come up in the last couple of years. I don't know if you've heard it, but it basically describes your body's ability to extract energy from whatever substrate is available at the time. So making it easier for your body to balance back and forth from fat to carbohydrates, it not requires so much of a gap. Bingo. Because usually the gap is what is it, like two weeks or something like that for you? If you're a carbohydrate. Yeah. And if you never go down the route of keto and all you do is eat carbs your whole life or have a carb-centric diet, you never get to the point where you're burning fat efficiently or effectively. Right. So you're really metabolically inflexible. Your body is just demanding that it continuously run on carbs and never tap into your fat stores. So you get typically you get incrementally fatter and fatter. And then if you skip a meal or skip two meals or try to go on some sort of a fast, the wheels fall off because you haven't built a metabolic machinery to burn fat, to burn ketones and all the things that go along with metabolic flexibility. So it turns out metabolic flexibility is the holy grail and how you get there, whether it's primal, paleo, vegetarian, vegan, fasting, IF, whatever. It's almost like it doesn't matter what route you use. If you can get to the point where you're metabolically flexible, now you have this ability to extract energy from your own stored body fat whenever you don't eat. And how does one do that? What's the best strategy? Well, the best strategy is keto. That's the best strategy. For sure. For sure. That's the best strategy. Because as long as you keep feeding your body carbohydrates every two or three hours all day long, the body goes, hey, I got plenty of fuel. Taking the carbohydrates in raises my blood sugar. Blood sugar is a fuel, but I don't want too much of it in my system. And so the body produces insulin, which tries to take excess glucose and protein and fat out of the bloodstream and sequester it in the cells. And in so doing, your blood sugar drops, and then you have to eat again every two or three hours. And it's this cycle that people enter into that they're on for a lifetime sometimes. And the tendency over time, because you're not burning your stored body fat, is to accumulate body fat. You never get really adept at burning body fat, because you never take time off to require that your body burns its fat. You just keep accumulating it. So how does someone go from being metabolically inflexible to metabolically flexible without going into keto? That's difficult. The way to do it is through fasting. And just keto is such a better way to do it. And the reason is you're trying to prompt the body into making changes that it doesn't want to make. When you go to the gym and you lift weights, you're prompting the body to build muscle that it really doesn't want to build, but now you're giving it a reason to. And so when you withhold carbohydrate from the diet, sugar in particular, but carbohydrate in general, and the body senses that it's not going to get glucose for a while, it starts to go to a plan B, which is to build the metabolic machinery to start to extract energy from stored fat cells, to burn that fat, to combust that fat in the muscle cells. It takes some of the fat, sends it to the liver to convert into ketones because the brain works really well on ketones. In fact, the brain works better on ketones than it does on glucose for most people. So the body has this built-in plan, this diagram, this genetic program that you're born with to be metabolically flexible and to be able to extract energy from fat and from ketones and from glucose. And it would normally go that route, but we never give it the reason to. Now how is that plan, how has it evolved? Well, for most of human history, we ate and we didn't eat. It wasn't like breakfast was the most important meal of the day or make sure you keep little Tupperware things of a little bit of protein and some carbohydrate to eat every two or three hours or else your muscles will go into cannibal mode. No, humans are wired to overeat. And because food was so scarce, when we did come across food, we tend to eat more. And certainly sweet foods like fruits was even more palatable, so we probably tended to eat more of that. But so we're wired to overeat and we have this amazing design that allows us to take excess energy and convert it into fuel that we carry around with us all the time, conveniently located above the center of gravity. So it's on the hips, on the butt, on the thighs, on the belly. So we tend to carry this excess body fat as a survival mechanism from a million years ago. That's why you carry it here? Yeah. That's sure. Like a fanny pack. Yeah, it's exactly what it is. It's exactly what it is. But again, if you look at evolution and how things work, we're bipedals. We have to stand upright. So if we had fat accumulating on our upper back or whatever, we'd be tipping over. So it's conveniently located over the center of gravity. It's an elegant, elegant design. The problem is it was designed so that when you didn't eat food, you could take that same fuel, take it out of storage, combust it, and not be any of the worst for wear. Not think of anything other than, I'm still going to hunt. I'm still going to do all these things. I haven't eaten for five days. I'm not hungry. I'm not pissed off at my mate. I'm just going to keep going with a great attitude that I'm going to find something to eat. Now, what is the standard amount of time? Is there a standard amount of time between if a person that eats a normal American diet and they just decide to fast, how long does it take before their body converts to burning fat? If they're not going keto? Right. Yeah. They're going to probably use a little bit of muscle in the process because the body, if it isn't used to deriving most of its energy from fat because of a process that you've engaged in to use keto to burn fat, it'll still seek glucose. If you don't give it glucose and you haven't done this work, for the first couple of days it's miserable. People talk about the low carb flu or if they go on a fasting thing at an ashram, I saw Elvis two days ago. Elvis? Whatever. I saw Elvis in my dreams. Oh, you're saying because you're going crazy? Because you're going crazy. Your brain is kind of frazzled because you haven't given it the opportunity to really thrive on ketones yet. Your body's making ketones, but you haven't built that metabolic machinery to use them efficiently and effectively. The brain's still looking for glucose. As a result, what happens is the brain will send a signal to the adrenals to secrete cortisol. Cortisol then goes throughout the body and strips amino acids from muscle tissue to send them to the liver to become glucose so you can feed the brain. It's counterproductive over time. It's also one of the reasons why back in the old bodybuilding days and the old training days in any gym, this mantra about don't go more than three or four hours without eating or you'll cannibalize your muscle tissue. If you haven't become fat adapted and keto adapted, that does happen. You do cannibalize muscle tissue when you go long periods of time without eating. When I say standard American diet, I don't mean junk food, but if you're a person who eats normal, you eat a little bit of pasta, a little bit of bread, but you eat mostly healthy. You decide that you're going to fast. Your body's going to cannibalize some muscle. Not so much. How much? A few pounds. A few pounds maybe. A few pounds. You'll get it back. You'll get it back. But the idea is that if you can weather that storm, how much time you're looking for before your body starts burning fast? Some people a week, some people two weeks, some people three weeks. You'll be dead. You can't fast for two weeks. Oh no, no, you're talking about fasting fasting. Oh Jesus. No, I'm talking about- No, I'm not talking about- No, no, I'm talking about intermittent fasting. That gets us to two meals a day. But what if someone just fasts? So give me a term. Okay, so you decide- You decide, I'm going to go on a 36 hour fast. That's probably the high end of what I would do, and then anything beyond that I'd be a little bit concerned that I hadn't prepped myself with fat adaptation yet. So when people go on these crazy three to five day fasts, they report all this energy. They feel great. They feel amazing. What's going on there? Their brains are using ketones. So that's definitely where the energy, the feeling of amazing comes from. Typically if you're fasting that long, you're not working out. Like, my wife does a seven day water fast twice a year. Oh Jesus. That's what I say. Do you go on vacation when that's happening? No, but I eat more. I eat for her while she's going. Why does she do that? She feels like it's good for her. She's into the autophagy and some of the anti-aging- Explain that. It burns cells that are- Yeah, so one of the many things that happens when you fast is that your body goes into a different mode and it starts to realize that there's not going to be a lot of fuel around for a while. And so in addition to burning stored body fat, in addition to making ketones, and by the way, ketones come from fat. So some of the fat that you combust is also just converted into ketones that your brain can use. The body also says, like if you had a brain, if you were a cell and you had a brain, you thought, well, generally there's a lot of fuel around. So my job is to pass the genetic material along to the next generation. So there's plenty for two of us. So I'll just divide and there'll be two of us and that'll be great. That same cell, in the absence of this sort of bathing in nutrition, goes, wow, there's not even enough for one of me, let alone two of me, so I'm not going to divide. I'm going to repair what I have. And so the cell goes into a repair process where it starts to consume damaged proteins and damaged fats within itself. It actually gets energy from that. Starts to repair broken strands of DNA or whatever little things are going on. Actually kills off senescent cells at that time. So it's an anti-aging strategy that a lot of people use. It's also a- God, I hate the term reset. Why do you hate the term? Because. It's overused. No, and I used it in a book, but all of a sudden, in the context of what's going on in the world and the great reset, I never want to hear that term again. Oh, the great reset, isn't that the conspiracy theory that the government is using this to change the financial structure of the country? And everything else. Yeah. Do you hear that a lot in Florida? Is that what's going on? No, no, we don't know. My NIH. No, no, no, we don't know, but I read a lot, Joe. I read The New York Times to see what the other side's doing. That's a great reset. Yeah, but so she will do these fast, but she's metabolically flexible. So it's easy for her to do. But if you're not metabolically flexible and you try to- you take on a fast of three days, you can get through it, and it's probably good for you. My whole thing is I want this to be, if you chose to do something like that, I want it to be pleasurable and easy and graceful and something you look forward to do, not something you dread doing. Now, is there a amount- can you intermittent fast and get your body to be more metabolically flexible in that way? Yeah, and that's what I'm talking about. So I'm not even into the multi-day fasting. I'm into two meals a day. So the premise of the book is once you've developed metabolic flexibility to engage in as much time as you can of not eating throughout the day to maximize all of these benefits that we just described that come from not eating. One of the things we say is most of the good things happen to us when we're not eating. Most of the repair, most of the recovery, most of the rebuilding happen when we're not eating. When we're eating, which we have to do, it comes with inflammation and it's a necessary thing, but the good stuff all happens when we're not eating. To the extent that we can expand that window of not eating and with the two meals a day program, which pretty much anybody who's keto now does, you just have an evening meal and then you don't eat until 1 o'clock, 1.30, 2 o'clock the next day. So you have two meals a day and you have that 18 hour window. That's what you use? Yeah, an 18 hour window. Why did you choose 18? It works for me. You can do 16, you can do, I mean anything less than 14 is back to sort of where you were before. It's a little bit better, but it's not as, like I said, the more time that you can go between eating, the better. It isn't about so much a routine on a daily basis. It's basically, I certainly use that as a template, but once in a while I eat one meal a day. I'll go dinner to dinner to dinner. The beauty here is because I'm metabolically flexible, I have the confidence that I'm not tearing down muscle tissue. I have that my immune system is probably benefiting from it as opposed to being somehow hurt by it. I maintain muscle mass. Again, I have all this energy and most importantly, I'm not hungry. Catch new episodes of The Joe Rogan Experience for free only on Spotify. Watch back catalog JRE videos on Spotify, including clips, easily, seamlessly switch between video and audio experience. 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