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Your Guide to Keto Fasting, with Dr. Joseph Mercola


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Keto fasting combines a very-low-carb diet with intermittent periods of fasting—and it has the potential to improve your sleep, cell regeneration, and gut health. Find out more about this lifestyle in this episode of RHR.

Revolution Health Radio podcast, Chris Kresser

In this episode, we discuss:

  • How Dr. Mercola got started with keto and fasting
  • Three benefits of intermittent fasting
  • How safe is fasting?
  • Fasting from an ancestral health perspective
  • The possible downsides of long-term keto and water fasting
  • How to start keto fasting
  • Tips on making keto fasting work for you

Show notes:

Hey, everybody, it’s Chris Kresser. Welcome to another episode of Revolution Health Radio. Really excited about the interview this week. I’m going to be talking with Dr. Joe Mercola. Dr. Mercola was trained as a board-certified family physician and treated over 10,000 patients before transitioning to focusing full time on his website 22 years ago. It has been the most-visited natural health site on the web for the last 15 years. He’s had many best-selling books, but his latest book on keto, Fat for Fuel, was the number one book sold in the US when it was launched in May of 2017.

Now Dr. Mercola has a new book out called KetoFast, and I’m really looking forward to talking with him about it because when I read it—he sent me an advance review copy—I was pleased to see that his approach to ketogenic diet and intermittent fasting and fasting is very similar to my own and what I’ve arrived at through my own experimentation and also through working with hundreds of patients in this combination of keto and fasting. And he has a lot of the same concerns that I do regarding ongoing ketogenic dieting in many people and in extended water fasting in many people.

And I really love the way that he’s put it together into a cyclical approach, with cycles of intermittent fasting and ketosis, and I think a safer and more tolerable way of getting the benefits of fasting without doing extended water fasting. So hope you enjoy this is much as I did. Let’s dive in.

Chris Kresser:  Dr. Joe Mercola, thank you so much for being here. I’ve been looking forward to this for some time.

Joseph Mercola:  Well, it’s a great pleasure to be with you. And I want to, before we begin, thank you so much for representing our views on Joe Rogan and really helping the world understand the truth about natural medicine.

Chris Kresser:  Oh, thank you for that. It was, it was arduous, but hopefully worth it.

How Dr. Mercola Got Started with Keto and Fasting

Chris Kresser: So I’m excited to talk about fasting, ketogenic diet, and in particular the approach you’ve outlined in your most recent book. And before we do that, I would love to just hear what took you down this road personally. How did you get interested originally in ketogenic diets and fasting and then how did you arrive where you are now?

Joseph Mercola:  Well, I was motivated to start keto because of the buzz about it a few years ago, and I wrote a book, Fat for Fuel, several years ago, which actually, the week it was launched, was the best-selling, the number one selling book in the entire country.

Chris Kresser:  Awesome.

Joseph Mercola:  By the Nielsen ratings. So I was convinced of the value of that approach metabolically and experienced some side effects from starting it myself, and learning by trial and error, I learned there’s some things that you should not do. And then I came to appreciate that fasting, complete multi-day water fasting, typically five days or so, was one of the most powerful metabolic interventions I’d ever seen and witnessed clinically.

And of course, historically, it’s been used for thousands of years, and virtually every major religion on the planet integrates some sort of approach. It seemed to make sense. So I wanted to follow up on my book Fat for Fuel. It was going to combine that with multi-day water fasting, and that was the intention of the book. And when I started to research it, I realized that I was wrong. So I modified it significantly to obtain the most amount of benefit you can with the least amount of work.

Chris Kresser:  Right.

Joseph Mercola:  Yeah.

Chris Kresser:  And potential downsides, which we’ll talk about.

Joseph Mercola:  Yeah.

Chris Kresser:  Because that’s definitely been my experience as a clinician too. It’s really interesting that when you look at the research on fasting, it’s like a miracle cure.

Joseph Mercola:  Yeah, yeah.

Chris Kresser:  You can find studies for fasting for just about every chronic disease and from severe autoimmune diseases to cancer to any inflammatory condition. But of course fasting, we can’t do it forever.

Joseph Mercola:  No, no, no you can’t. But the most frequently you can, the better benefits you get.

Chris Kresser:  Right.

Joseph Mercola:  Let me just interrupt by saying that there is one benefit that I neglected to mention in the book, but I realized after writing it is that the fasting benefits on your sleep are extraordinary. Do you wear an Oura ring at all?

Chris Kresser:  I do, yeah.

Joseph Mercola:  All right, so then you know that when the days that you’re fasting, oh my gosh. Your readiness score goes through the roof.

Chris Kresser:  Yeah, it’s pretty incredible. All that tissue repair, which I definitely want to do a deeper dive into that. But you have a section in your book on the history of fasting, which I think is interesting. Because it’s been around for a really long time. You could say it’s maybe one of the original health interventions.

Joseph Mercola:  Absolutely, there’s no question. It’s been used for thousands of years. I mean, we’ve got Plato and Hippocrates promoting it 2,000 years ago. And it started in the US about the 1800s with the national hygiene movement.

Chris Kresser:  Right.

Joseph Mercola:  It didn’t really become popular until Herbert Shelton started and popularized it in 1911, about 100 years ago. And today we’ve got Alan Goldhamer out in your neck of the words in the TrueNorth clinic in Northern California who had fasted more people than anywhere in North America, at 16,000 people, from anywhere from five to 40 days.

Chris Kresser:  Yeah. And then there’s a lot of other benefits too, of course. I think for me personally, just looking at my relationship with food, which fasting illuminates, and not cooking and cleaning, I have to say—I appreciate that a lot on a day when I’m busy—I love food probably as much as anybody I know, and cooking and food preparation, and I’m a total foodie. But I have to say that occasionally I just get tired of the whole process.

Joseph Mercola:  I’m actually surprised to hear that. I thought you’d be a little bit more oblivious to it.

Chris Kresser:  Oh, no.

Joseph Mercola:  You eat to live.

Chris Kresser:  I love food. I mean, I cook all the time. I love going to farmers markets. I’m a total foodie, but there are times when I need a break from it and I love what fasting does for that too.

Three Benefits of Intermittent Fasting

Chris Kresser: So, let’s talk a little bit about some of the mechanisms of fasting. I’ve touched on this in previous shows, but you do a pretty deep dive in that in your book.

Keto fasting could benefit your cellular health, your gut integrity, and your sleep. Check out this edition of RHR to learn more about how to combine keto and fasting, as I talk with Dr. Joseph Mercola. #lowcarb #keto #chriskresser

So, you talk about autophagy, of course, and several others. And there’s been a lot of focus on stem cells and other ways of addressing stem cells, which maybe are not quite as safe or as well proven at this point. So why would we consider fasting in terms of the cellular benefits?

1. It Improves Your Sleep

Joseph Mercola:  Sure, well, I think one of the most important ones is the issue with the sleep, which I just mentioned. So, I mean, sleep is close to, if not nearly, as important as getting the food right.

Chris Kresser:  Yeah.

Joseph Mercola:  And many people don’t appreciate that.

Chris Kresser:  Yeah.

Joseph Mercola:  So, and I’m sure you’re not one of them, I know. But a lot of people don’t. I certainly didn’t until I read Matthew Walker’s book.

Chris Kresser:  Yeah, great book.

Joseph Mercola:  He just did a good interview, a two-hour interview with Rhonda Patrick on her podcast. But it’s powerful. But getting back to autophagy—and I’m sure most everyone listening to this has heard it before but let me just summarize it before, because some maybe have not heard it previously.

2. It Activates Autophagy

So, it’s, in my viewpoint, the primary reason why you want to fast is to activate autophagy. And what does autophagy mean? It means that your body essentially identifies defective and dysfunctional cellular parts, not whole cells, because the process for that is called apoptosis, but these cellular parts, these organelles, it targets them and then lysosomes latch onto them and they release these digestive enzymes to break it down to constituent elements, amino acids and fatty acids, and then it recycles them into new parts. And that’s the other benefit is that you get regeneration, which is what you get after you fast.

So the magic of fasting really, I mean certainly there is some of the expenses you mentioned, you say the time, effort, and energy, your mental clarity improves. But the primary benefit is when you re-feed and you give your body the raw materials to rebuild new cellular parts.

Chris Kresser:  I don’t think that’s well understood, actually. And I think, I really love how clear you made that in your book, and especially when it comes to refeeding, which we’ll talk about earlier, is one of the ways of addressing the potential downsides of fasting and doing it cyclically. I don’t think it’s well understood that some of the main benefits you get from fasting occur only when you start eating again.

Joseph Mercola:  That’s right. And that’s one of the reasons, one of many reasons why I don’t recommend long fasts. Because you don’t get as many cycles in there.

Chris Kresser:  Right.

Joseph Mercola:  And in addition to when you’re fasting, as I mentioned with the sleep, your readiness score goes through the roof. That means you’re able to really workout hard and you have the energy to do it. And so I do this keto fasting twice a week, and I do it the days before I work out hard on my strength training.

Chris Kresser:  Right.

Joseph Mercola:  And then I do that fasting and then I go and have lots of protein, lots of carbs, and it just is a fabulous way to improve your metabolic health.

3. It Improves Your Gut Health

Chris Kresser:  Yeah, so, I want to get a lot more into the different ways to do it in a little bit. Because I think that’s where the magic happens, how you actually set it up and make it work and cycle it along with your training regimen, etc. But another thing I think we’re both interested in in terms of fasting is gut health.

Joseph Mercola:  Yes.

Chris Kresser:  So, I see a lot of patients who have SIBO and all kinds of long-term G.I. issues. And maybe they’ve done several treatments for SIBO, they’ve taken rifaximin and we’ve done botanical protocols and other strategies. And either it goes away for some time and comes back, or it never goes away at all. And I’ve become increasingly interested in fasting and  ketogenic diet and cyclical keto and fasting as a tool for addressing these conditions. So can you talk a little bit about that?

Joseph Mercola:  Yeah, I couldn’t agree more. Because, and I’m not sure that anyone understands exactly the mechanism, but more than likely it’s a jump start to your microbiome health. It improves the diversity and helps repair some of the leaky gut issues with these, you have these, essentially, spaces within the membranes in the intestine where large molecules can leak through and cause major problems.

So it really facilitates healing of that permeability through a break, a pathway, and enhances the integrity of your gut lining. So, I like it for that purpose. It’s sort of a side benefit. I don’t look as it as one of the main benefits, but so many people suffer with this issue. So it’s really nice.

Chris Kresser:  Absolutely. Yeah, I mean, we know from the research that the elemental diet, which I’m not recommending here, but it’s the most effective treatment for SIBO. And I think what happens with the elemental diet is even more powerful with fasting. You’re just giving, you’re starving the bacteria that are overgrown in the small intestine. You’re not giving them any food source, they can’t proliferate, and it turns out more effective even than antibiotics.

So, I’m curious to do, we occasionally have been using uBiome and other labs to do serial testing of the microbiome with interventions like this. So, I have an idea when I was reading your book that maybe we’ll put some patients on the keto fast approach and do some before-and-after testing with uBiome and see what we can detect.

Joseph Mercola:  Yeah, please update me on that. That sounds like an interesting study.

How Safe Is Fasting?

Chris Kresser:  Absolutely. All right, so we’ve talked a little bit about the history of fasting, the mechanisms of fasting and why it works. What about safety and contraindications? Because you see, there’s a lot of, I think, misleading claims made about fasting, like it’s really dangerous. And on the other hand, I think there’s also some irresponsible claims made about fasting and not enough attention in some ways about who shouldn’t do it. So where do you come down on this?

Joseph Mercola:  Well, thank you for bringing that to everyone’s attention because sometimes it’s something I fail to mention. But you are absolutely correct. Fasting is not for everyone, at least partial fasting or certainly multi-water day fasting. But that’s a relatively small minority of people, and who are those people? People who are underweight who don’t have enough body mass, we’d sort of obviously not want to fast. Or if you have an eating disorder, that would only exacerbate it. And then those who, if someone’s pregnant or even nursing—

Chris Kresser:  Right.

Joseph Mercola:  So those aren’t, that’s not a large number of people.

Chris Kresser:  No.

Joseph Mercola:  Probably far less than 5 percent. My guess, even less than 1 percent of the population.

Chris Kresser:  Yeah, yeah. Just good to know. I’ve had pregnant women ask and nursing women ask me about fasting. So I always like to make that clear. Because when you’re pregnant or nursing, you’re really trying to build up and feed the growing baby. That’s the priority there.

Joseph Mercola:  Yeah.

Chris Kresser:  But of course.

Joseph Mercola:  Anabolism is the key.

Chris Kresser:  Yes, yes, absolutely.

Joseph Mercola:  And that’s the beautiful thing about fasting is you cycle between anabolism, catabolism, and virtually no one’s doing it. And I’m sure you’re familiar with Satchin Panda’s work?

Chris Kresser:  Yeah, yep.

Joseph Mercola:  Where 90 percent of people are eating more than 12 hours a day and that isn’t even sufficient for intermittent fasting.

Fasting from an Ancestral Health Perspective

Chris Kresser:  Yeah, absolutely. It’s like a constant grazing that’s happening. The cyclical thing is really interesting to me because I know you and I both really appreciate the ancestral perspective. And if you think about, like, what likely happened in a natural and evolutionary environment, people were not voluntarily fasting. But they had natural periods of food scarcity. And then those periods of food scarcity were naturally followed by periods of food abundance after they killed an animal or something like that.

So our bodies evolved in this environment of cyclical periods of food scarcity and food abundance, and it makes sense that our metabolic machinery would be adapted to work that way. So I love how this approach really mimics that.

Joseph Mercola:  Yeah, and you know, sadly, Chris, I don’t think there’s many approaches that are replicating this pattern. It’s just like it’s an all-or-none component.

Chris Kresser:  Right.

Joseph Mercola:  You go all the time or you don’t do it and maybe some people are doing cyclical keto. But the integration in the partial fasting is, I think, the missing key piece.

Chris Kresser:  That’s where we agree 100 percent on this too. I was so happy to see your book because that’s the approach I had naturally settled on in my clinic. Because I had seen, actually, a lot of the downsides of 24/7 ketogenic dieting and excessive fasting. So I know that you experienced some of those yourself. You mentioned that. Let’s talk about that. Let’s talk about some of the downsides of ongoing keto and ongoing, the dark sides of water fasting.

The Possible Downsides of Long-Term Keto and Water Fasting

Joseph Mercola:  Well, there are two separate issues. Because if you’re doing keto continuously, as some people advocate, I think most people are going to run into problems primarily with their hormone systems, and specifically your thyroid. You develop some thyroid resistance, but then you’re really in this constant catabolic phase where you’re just breaking down your body, and that’s good, but you need to build it up.

But the common belief is certainly, was what I understood when I first started, that this was like the diet you should be on forever. And I learned very quickly it’s a bad idea because after a few months you start losing muscle mass, which is not a good strategy, especially as you’re aging. And sarcopenia just kicks in almost relentlessly.

Chris Kresser:  Yeah.

Joseph Mercola:  So that’s the primary component. And then you’re not, that regeneration component, the feasting part is missing. And that is that the massive, almost magical benefits you get by integrating that in a cyclical fashion.

Chris Kresser:  Yeah, I’ve also seen even with people who had phenomenal results with keto for weight loss initially, that they hit a plateau or even start to move back in the other direction. And it’s been, in some ways, challenging for me, my approach with them was usually to actually have them start eating more carbohydrate, which seemed counterintuitive to them because they had such great results from doing keto initially. But that can often kickstart the weight loss process again. And I think you’ve explained why in the book in terms of how all those mechanisms get engaged when you start the refeeding process.

Joseph Mercola:  Right.

Chris Kresser:  And then what about water fasting? This is a powerful strategy. It’s something that’s got a lot of history behind it. But what are some of the downsides there?

Joseph Mercola:  Well, one of the primary downsides is that it made a lot of sense historically and that’s why it was done for thousands of years and is still done. But we live in a different century. The 21st century that didn’t exist previously, obviously. And one of the major contributions within the last hundred years is that we’ve had the chemical industry make loads of chemicals. Tens of thousands of different chemicals.

And most of these chemicals are fat-soluble. And being fat-soluble, they tend to wind up being stored. Not metabolized, but stored in your fat cells. So when you do this multi-day water fasting, especially without eating any food, you’re doing two things. One is you’re liberating the toxins, and most people—and I know you have great experience with this—are not metabolically healthy enough to metabolize those toxins. As a result, they have the side effect. Almost everyone’s aware of people who are water fasting, they feel miserable.

Chris Kresser:  Right.

Joseph Mercola:  And it’s largely, I believe, is a result of these liberated toxins that are not properly metabolized and excreted. So that’s one. The other, as a clinician you’re deeply aware of this too, is compliance.

Chris Kresser:  Yeah.

Joseph Mercola:  Compliance for this in the general population is well under 1 percent. You’re going to have to almost kill someone before they’re going to want to do multi-day water fasting.

Chris Kresser:  Yeah, it’s true.

Joseph Mercola:  So it’s just a pragmatic approach.

Chris Kresser:  Yeah.

Joseph Mercola:  So that is, those are the two big ones. But another practical one is that if you’re going do a multi-day water fasting, I mean, unless you’re massively overweight and there are some people who have lost 300, 400 pounds doing that, you’re only going to be able to do it a few times a year. Initially you might be able to do five, six, seven times the first year, but after that, probably not more than once a quarter, which means you’re only going to cycle in and out and get these refeed benefits like five times a year. Which is, like, virtually clinically insignificant. So, yeah, you’ll get some really great benefit when you refeed, but you have to refeed differently when you haven’t been eating for a few days. But if you’re doing this the keto fast, you can do that 100 times a year.

Chris Kresser:  Yeah, it’s pretty amazing, if you’re doing it twice a week.

Joseph Mercola:  And you get these benefits twice a week.

How to Start Keto Fasting

Chris Kresser:  Yeah, yeah that’s pretty amazing. So, yeah, let’s talk about, let’s go into this now, and why don’t you define keto fasting for everybody? And then we’ll kind of talk, get into some of the nitty-gritty details about how you sequence it with your exercise routines and also how you transition into it. Because I like how you provided a kind of on-ramp for people who don’t have experience with this so that they’re avoiding some of the potential downsides if they just start whole hog.

Joseph Mercola:  Yeah, well, I don’t think you can start whole hog. And you have to be metabolically flexible. Your body has to have the capacity to burn fat as a primary fuel. And over 80 percent of the people in this country, as you’re well aware of, are insulin resistant. And these people cannot do keto fasting initially. They have to transition into it through a program of doing calorie restriction, and my favorite, of course, is intermittent fasting.

Compress Your Eating (And Allow for a Transition Period)

Joseph Mercola: So, and it’s not just a 12-hour. Because I don’t think virtually any benefits occur 12-hour. It probably starts at 14, but I think you’re going to get most of the benefits from 16 to 18 hours of a window where you’re not eating. So, otherwise eating within a six- to eight-hour window a day. Which is the exact opposite of what most people eat.

Chris Kresser:  For sure. And during that intermittent fast period, there are a lot of different ways that are recommended to do this. Some recommend just water and non-caloric beverages only, like black coffee or black teas. Others say it’s okay to have a little bit of fat in the coffee or tea during the intermittent fast period. Where do you land on that?

Joseph Mercola:  I like to go with the no calories, because I really want to try to get as much benefit from autophagy. And certainly most calories will tend inhibit autophagy. But in the transition, the initial four-week phase that I recommend that everyone do, and unless they’ve been doing it … Like, you could start this thing this week, because you’re doing it. But if you haven’t done that, then you need to essentially work up to the point where you’re only eating within six to eight hours. And then do that for four straight weeks. Now, during that transition phase, I think it’s okay to have a little food and snacks, especially coconut oil or MCT oil, if you’re feeling fatigued. Because your body needs to become metabolically flexible, and you aren’t yet. So you’re going to need some fuel source. And those types of fats will rapidly be absorbed and converted to energy so you’ll feel better. But once you’re doing it, then I don’t think it’s wise to,  at least from my perspective—

Chris Kresser:  Right. So you compress your eating window to six to eight hours for one month, and that’s no calories during that period unless you need a transition period where you’re having maybe a little bit of fat during that time. And then what? What’s step two?

Eat Your Last Meal at Least Three Hours before Bed

Joseph Mercola:  Well, this is what I’ve learned from trial and error. So, let’s say you’ve done, you have a six-hour eating window. So your first meal is at 9 a.m. in the morning, your last meal is at three.

Chris Kresser:  Three, yeah.

Joseph Mercola:  So the one caveat in that intermittent feeding window is to make sure that your last meal is at least three hours before bedtime, which can be a social challenge for many people. But I think metabolically that’s what your goal is. And if you do eat a meal in that time, make it really, really light.

Chris Kresser:  Right.

Joseph Mercola:  You do not want a lot of energy when you’re sleeping. That is an unwise time to load your body with fuel. So your last meal was at three o’clock in the afternoon. You come around to eat breakfast at nine, which would be the normal day, the time that you would eat. So instead of eating your regular meal, you only have, like, one meal. And that meal is about, it’s anywhere from 300 to 500 calories.

Plan Your Calories Carefully

Joseph Mercola: Essentially you take your lean body mass and you multiply times 3.5 and then you come up with the calories. So, and that’s your meal for the day. And you don’t eat anything else for 24 more hours. So essentially, you’re doing a partial fast of 42 hours on, say, 500 calories. And that is the magic, and I’ll refine the details in a moment. Because I’ve been intermittent fasting for six hours for years now and I don’t lose weight when I intermittent fast. Assuming that I’m meeting my appropriate number of calories.

But the moment I do a partial fast, I’ll lose anywhere from three to five pounds the next day, which is a good thing. Most of it’s water of course. It’s not lean body mass. It’s water. But you still lose. You don’t lose that weight when you’re intermittently fasting.

Chris Kresser:  Right.

Joseph Mercola:  That’s a strong suggestion that there’s something very significant going on clinically when you do this.

Chris Kresser:  Okay, so that’s your keto fast day. So you’ve been intermittent fasting for a while, you’re fat adapted and you add a keto fast day. You’re eating between 300 and 600 calories, depending on your lean body mass. And you go through this very clearly in the book. There’s a great chart actually, that takes you through this, which I found to be very helpful. And then—

Joseph Mercola:  Well, let me be specific on what that food is, though.

Chris Kresser:  Yeah.

Joseph Mercola:  We actually have a companion KetoFast Cookbook where you can actually create meals that are designed to do this. But what I do to simplify it is—and I’ve actually modified it somewhat since the book was published—is that 50 percent of those calories, I believe, should be protein. Because that’s going to fuel your detoxification system.

So anywhere from 20 to 50 grams or so. But here’s the key, and okay, let me finish this off. So you’ve got protein, but you maybe have less than, certainly less than 20 grams of carbs and ideally less than 10, and the same amount of fat. So relatively small amount of fat and carbs, and protein. But it’s a very specific type of protein. This is not a hamburger. This is not really even meat. This is plant-based protein, for the most part.

The exception would be collagen, which is very, very low in branched chain amino acids, which will stimulate mTOR, which is the last thing you want to have when you’re trying to activate autophagy. Because those branched chains will activate mTOR and inhibit autophagy. So collagen has virtually none of the branched chains and plant-based proteins. We’ve got a vegan-based protein powder that I absolute love. So I have that, some collagen and some chlorella to make up those protein on those days.

Chris Kresser:  Okay. So, you’re eating a certain amount of protein, you’re keeping the carbs under 20 grams or even 10, and then the remainder of whatever your calorie is between 300 to 600 would be fat.

Joseph Mercola:  Yes.

Chris Kresser:  Okay. So then you do that, and then is your refeed day the next day?

Joseph Mercola:  It is the next day. But there’s one more caution. Because most people are taking supplements and many people have identified themselves as having an MTHR genetic SNP—

Chris Kresser:  Yeah.

Joseph Mercola:  So they’re taking methylfolate or methyl B12. So on those, the day that you’re keto fasting is the day that you do not, do not take methylfolate. Do not take methyl B12. And why is because those are pretty much anabolic supplements. These are supplements that pregnant women take to build their baby. So the last thing you want to do is stimulate anabolism. You want to stimulate catabolism. So don’t take any methyl B12 or methylfolate. Or colostrum would also do something similar, or even ketone supplements—

Chris Kresser:  Right.

Joseph Mercola:  Like ketone esters, because what happens, it’s really interesting. The ketones essentially break down the butyric acid, or butyrate. And the butyrate will actually increase acetyl coenzyme A, which also inhibits autophagy. So just let your body make its own ketones. You don’t take any extras.

Chris Kresser:  Yeah, okay. So we’ve got those cautions for the fast day, and then how do you approach the refeed day?

Joseph Mercola:  Oh, the refeed day is the feast day.

Chris Kresser:  The fun day, yeah.

Plan Your Refeed Day

Joseph Mercola:  There’s not too many limits on it, other than high-quality foods. But I would go crazy with the branched chains. That’s the days I have the whey protein. I have lots of whey protein. And that’s the day that I think strength training. That is the day that you really push it very hard, stress your body, because your sleep is going to be through the roof. It’s going to be unbelievable. And you’ll be able to workout very hard, so then you have lots of good protein. Maybe 25, 50 percent more than you normally have. And you give your body the fuel to rebuild your tissues.

Oh, the other benefit that happens is that when you, during the partial fast, you’re going to activate the stem cells. I know you mentioned it in the intro, but we kind of slid past it. And there’s a lot of people nowadays who are advocating stem cells, whether autologous or otherwise. And first of all, it’s very pricey. I mean, the minimum is $5,000, but more likely $10,000 or $20,000, and I’m sure some people get benefits. But there’s no question there’s a cost to it. And there’s some concern about the safety of these things too. But I think it’s a far better approach to use your own cells and to activate them, which, clearly, keto fasting will help activate.

Chris Kresser:  Absolutely. And for the, you said maybe double your typical protein intake, you’re still eating this during your six- to eight-hour window.

Joseph Mercola:  Yes, yes. There’s no change there. Right.

Chris Kresser:  Just to clarify. And then what about carbohydrate ranges for people?

Joseph Mercola:  Yeah, I think that I wouldn’t go a lot more than 150 grams of carbs. But those are the days when you have a lot of carbohydrates. There’s no question about it.

Chris Kresser:  Right. And 150 is going to feel like a lot more than 10 the previous day.

Joseph Mercola:  Yeah.

Chris Kresser:  That’s going to feel like a feast, like you said. It’s going to be massive.

Joseph Mercola:  Yeah, it is actually a feast. In fact, most of my days I feel like I’ve had on Thanksgiving.

Chris Kresser:  Right.

Joseph Mercola:  Just, I’m stuffed to the max. I’m eating somewhere about between 4,000 and 4,500 calories.

Chris Kresser:  Right, okay. So sequencing this, you’ve got your intermittent fast day, you’ve got your keto fast day, then you’ve got, follow that by a refeed day, and I know from your book and just talking to you, you’re doing two keto fast days a week. So you recommend between one or two, depending on the goals and what’s going on for that person.

Joseph Mercola:  Yeah, and sometimes I’m not able to do that because I’m traveling. And when I’m traveling, I don’t have the luxury of maintaining my weight. Because if my weight is below a certain threshold, I will not do a keto fast day because I’ll lose too much weight.

Chris Kresser:  Right, yeah. And what is that threshold for you in terms of, you mentioned low lean body mass as a contraindication for fasting.

Joseph Mercola:  For me, it’s, I think, I’m probably, I’m under 10 percent body fat and I … like my basal weight is, I don’t like to go below 175. I try to get to 185 and I’m typically, I’m getting closer and I’ve gotten closer there since I’ve started increasing the protein on the partial fasting days.

Chris Kresser:  Yeah. And just so everyone knows, you’re a tall guy. I was surprised when I met you. Because I’m tall. I didn’t know you were as tall as you are. So 175 is pretty lean for someone your height.

Joseph Mercola:  Yeah. So I’d like to put on a little muscle mass. This year I turned 65, so sarcopenia becomes an issue. Fifty percent of people who are 80 years old have lost most of their muscle mass.

Chris Kresser:  Yeah.

Joseph Mercola:  So you’ve got to be aggressive and prevent that inevitability.

Chris Kresser:  It’s super important for healthy aging. I learned that a while ago and I think it doesn’t get enough attention. Which of course is why strength training is so important as you age as well.

Joseph Mercola:  And interesting—and Jason Fung addresses in his most recent book, The Longevity Solution, I think, I’m not sure of the exact title, but it’s his most recent book—that your needs and requirements for protein increase as you age.

Chris Kresser:  Yeah.

Joseph Mercola:  So it’s a little counterintuitive.

Chris Kresser:  It’s kind of backwards for most people. A lot of people develop low stomach acid and GERD, and so they can’t tolerate as much protein when they age. And they end up eating less, I think.

Joseph Mercola:  Yeah, yeah, absolutely.

Chris Kresser:  So we got two, if you’re doing the full approach, you’re doing two keto fast days a week. Then you’re doing two refeed days a week. So then that leaves three days of the intermittent fast compressed food intake, right?

Track Your Nutrients

Joseph Mercola:  Yeah, and whatever norm of calories that work for you in ranges. So, I mean, I go over them in my previous book, Fat for Fuel. And another interesting tool that many people may be unaware of is cronometer.com. It’s c-r-o-n-o-m-e-t-e-r. And I don’t think any expert would disagree that it is probably the finest nutrient tracker out there. It’s basically free if you use it on the desktop, and we actually have, if you put “/mercola,” you get one specifically designed for keto fasting.

Chris Kresser:  Yeah.

Joseph Mercola:  So it’s a really good tool. Have you used it before, Chris?

Chris Kresser:  We use it all the time with our patients. I mean, there’s certain nutrients, as you know, that you can’t really measure very accurately in any body fluid. Like calcium. So we’ll often have people track their nutrient intake with this and get a sense of where they’re falling short in their diet. And what you learn is, in many cases, people are not getting enough nutrients, even when they’re on a “healthy diet.” So it’s a really super-important tool and you can, I love the way you’ve set it up. You put your body type in there and your conditions and what you’re trying to do and then it can give you the actual what you’re shooting for with keto fast.

Joseph Mercola:  Yeah. It’s a really elegant system. I’m so delighted that Aaron was open to modify. And he initially designed the site for longevity because life extension is one of his primary goals. And it just happens to be, work out really well for this. Now life extension is one of my goals, which is one of the reasons I wrote this book. Because I would love to live beyond 120, which is not really physiologically possible at this point in time. But, so, the strategy that most of us are using is stay as healthy as you can, which has a lot of other benefits, until there’s some changes in the technology which might allow us to jump past that physical barrier.

Chris Kresser:  Yeah, absolutely. And with the way things are going, it’s not at all inconceivable that that can happen.

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Tips on Making Keto Fasting Work for You

Chris Kresser:So let’s kind of talk about some tips and tricks, so to speak, to make this work. So let’s say someone’s relatively new to fasting and they’re really struggling with appetite cravings during their periods of either the intermittent fasting or on the keto fast day. What do you suggest there?

Expect Cravings—At Least at First

Joseph Mercola:  Well, that’s the beauty of intermittent fasting, at least after you’ve done it for a while and your body’s developed the metabolic flexibility to access your fat stores, break them down and create energy out of them. So, initially, if you’re part of the 80 percent of the population who is insulin resistant, you’re not able to do that or do that well, then you’re going to have cravings. That is normal. This is natural.

It’s exactly what you’d predict and expect because your glucose levels have dropped and you need energy to burn. You can’t burn the stored fat that you have in your body. It’s just inaccessible to you as an energy source. So what you have to do is sort of struggle through it, and for most people it’s typically not longer than two or three weeks unless you’re really metabolically damaged, and in that case, it may take a few months. But in that process, you can, as I think mentioned earlier, you can have some healthy fats like coconut oil, which is probably the least expensive. And even better would be MCT oil. And even better than that would be a caprylic acid, or C8, which is a subtype of MCT oil, it’s just a little bit more expensive. But the benefit of these is they all convert to eventually ketones or fatty acids that are a) easily digested so you don’t you take enzymes with them, and then b) rapidly converted to energy and can give you that missing energy you need until your body is able to make the transition.

So once you’ve achieved that flexibility though, which I said for most people is going to be within that month that you’re doing the intermittent fasting, then you’ll know. You just aren’t hungry, and I’m sure you can testify to this as can hundreds if not thousands of your patients who have made this transition, is hunger is not an issue.

Chris Kresser:  Yeah. Yeah, it’s actually the opposite. In my experience and in the experience of many of my patients is when that ketone production starts, you get less hungry and you can actually go for longer periods without feeling those cravings. Even then, when you’re eating food, which is really again, counterintuitive for most people, but I’ve had so many people say that. And that’s been my experience too.

Joseph Mercola:  Yes, it’s just amazing. So that doesn’t discount the fact that some people may have a psychological craving. Not a physiological, but a psychological. And they just want something in their mouth, want to chew on something.

Chris Kresser:  Absolutely.

Joseph Mercola:  So what I do, I have the good fortune of living in Florida. So I have over a thousand aloe plants. And every day I cut off, like, two or three leaves and I just suck on the gel. I think that has a lot of good health benefits aside from helping address that issue. Which I don’t really need it for that issue. But it’s kind of nice. It’s just like you’re chewing on something that essentially has no calories.

Chris Kresser:  Right, yeah. Absolutely. So another thing that we both are big believers in, which I mean I sometimes think of, if we’re thinking about optimizing health, also optimizing health span. Not just life span, but health span. What are the biggest levers? Obviously, a healthy, nutrient-dense, real-food diet, I think fasting and periods of ketosis are at the top of the list. And I would also put sauna at the top and hot and cold and possibly cycling between those two at the top of the list too.

Complement Your Fasting with Sauna

Joseph Mercola:  Yes.

Chris Kresser:  And I know you’re a big believer in that too. So how do you cycle sauna use into this protocol or this approach that you’re doing? Tell us a little bit more about your approach there.

Joseph Mercola:  Yeah, well, I’m absolutely on the same page as you. There’s no question that I believe that this cyclical use of exposure to hot and cold will help improve your health. It’s just pretty well … there’s many studies that strongly suggest, that’s certainly the Finns, but they use a traditional sauna, which is a little bit more challenging than what is readily available in the US since you go to one of these big institutions.

Chris Kresser:  Right.

Joseph Mercola:  So what most people are using in their home, because it’s so much more convenient … and in Finland almost everyone has a sauna in their home, right?

Chris Kresser:  Yeah.

Joseph Mercola:  I don’t think you can feel at home without a sauna.

Chris Kresser:  Pretty much, yeah. They’re just there.

Joseph Mercola:  But it’s miserably cold there most of the year.

Chris Kresser:  Yeah, yeah.

Joseph Mercola:  So, anyway, here in the US we don’t do that. So most people have resorted to using infrared saunas. And that was to have been the rage for a long time. There’s some major problems with them which I’d like to address. So they initially started as the far-infrared saunas and almost all the initial units had really high EMF, specifically the magnetic fields. They were through the roof. So you’d be damaging yourself from a molecular perspective from exposure to these frequencies.

But then we … there’s other issues with that. And I was convinced that you could modulate the far-infrared to be the best sauna, so much so that when I was at Bulletproof in 2017, there was an exhibitor there named Brian Richards who founded the company SaunaSpace. And he seemed like a bright guy, so I went and had a discussion with him. I wanted to be respectful, but my intention was to sort of decimate him with these arguments. And it turns out the exact opposite, and he decimated me. Because he converted me to this understanding of the amazing benefits of near-infrared saunas.

Chris Kresser:  Yes.

Joseph Mercola:  And one of the primary ones is that the sun, people don’t understand it, but 40 percent of rays from sunlight radiation are infrared.

Chris Kresser:  Yep.

Joseph Mercola:  Mostly near-infrared. I mean there’s some far, but it’s mostly near. So that would strongly suggest that regular exposure to these frequencies is probably a good idea.

Chris Kresser:  Yep. And just so you know, I have a SaunaSpace.

Joseph Mercola:  Oh, you do?

Chris Kresser:  And Brian has been on the podcast. I have the EMF-free SaunaSpace.

Joseph Mercola:  Oh, I’m so glad to hear that.

Chris Kresser:  So, yeah, we’re big believers in that as well.

Joseph Mercola:  Yeah, I love Brian. I did an interview with him too and he’s just, I mean, he absolutely converted me to this understanding. So I’m preaching to the choir with your group.

Chris Kresser:  With the listeners, yeah.

Joseph Mercola:  Yeah, yeah. So I’ll skip over that. Just listen to your previous interview.

Chris Kresser:  Oh no, it’s great. I’m just curious like how do you, do you time, do you do any specific timing with the sauna?

Joseph Mercola:  Oh yeah, yeah. Well, I was going to go further into the details of the difference between the far and the near. But let me just mention that, you have the EMF-free one?

Chris Kresser:  I do, yeah.

Joseph Mercola:  Okay. Now, so then you know. That’s the exact same one I use. And it is, in my view, the best sauna on the market. It is not the most convenient sauna to use or practical, but it is the best from a health perspective. Because it helps put your body into a parasympathetic mode.

Chris Kresser:  Yeah.

Joseph Mercola:  Because you’re shielding all the frequencies coming up. The whole sauna is grounded and you’re just getting these healthy benefits and just putting your body in a state which you could benefit from to detoxify.

So one of the, as I mentioned or alluded to earlier, when you’re doing the partial fasting, unlike intermittent fasting, even in intermittent fasting, you’re going to stimulate autophagy to a degree. But a relatively minor degree compared to what you do with keto fasting. So the morning after your keto fast, you are really going to be excreting toxins. So one of the ways that you can help facilitate the excretion of those toxins through your sweat is through regular use of the near-infrared sauna.

Now if you can’t afford the $8,000 of the EMF-free SaunaSpace, and many people can’t and there’s nothing wrong with that, then you can get a less expensive version. They sell them, SaunaSpace does, of course, but you can even go and use sauna therapy by purchasing the book Sauna Therapy for Detoxification and Healing by Lawrence Wilson and make one yourself.

Chris Kresser:  Absolutely.

Joseph Mercola:  Just be careful in choosing the materials wisely because you are heating this thing up. And if you’ve got toxic materials in there, you’re going to be breathing them in and you’re just sort of defeating your purpose of doing it.

Chris Kresser:  Yeah. And just to clarify to the listeners, the basic SaunaSpace unit, the bulbs are shielded from EMF. So they’re in Faraday cages and you’re not getting EMF exposure from the bulbs. The difference with the full EMF protective units is that it’s shielding EMF from outside of the sauna, from coming in. And so it’s got a liner around the whole sauna that keeps ambient EMF from coming in the sauna. So I just wanted to clarify that Brian’s really good about, even with the basic sauna, that there’s no EMF exposure from the bulbs themselves.

Joseph Mercola:  Yes, and part of the reason for them, let me continue to improve the clarification, is that not only is the shielding there, but that shielding is grounded.

Chris Kresser:  Right.

Joseph Mercola:  Which allows to dissipate the electrical fields that you’re exposed to straight down to the ground. So you’ve got to be careful about the grounding component too.

Chris Kresser:  Absolutely. So, just to put this all together, the week would look like you’ve got your intermittent fast day, a keto fast day. The next morning would be sauna use, and then that’s going to be your hard strength training day and your refeed day.

Joseph Mercola:  Yeah, and let me tell you another benefit that’s happening, because I forgot to mention this—and I’m not even sure if I put it in the book—but when you are partial fasting, your growth hormone increases by about 200 to 300 percent.

Now, you’re going to say that doesn’t make sense. How does that happen? Because we know that growth hormone normally stimulates IGF-1, and when you have IGF-1, that is an absolute shutdown for autophagy. But what happens is that the liver becomes relatively—where many of these growth hormone receptors are—becomes resistant. The receptors to it become resistant. So you do get lower IGF-1 levels. But you still get the high growth hormone.

So what you want to do on the days of the partial fast before you eat your magical refeed feast, that’s when you strength train. You do not eat food while you’re strength training. Do it fasting.

Chris Kresser:  Important clarification.

Joseph Mercola:  And you’ll radically improve the benefits.

Chris Kresser:  Yeah, absolutely, important clarification there, just for sequencing. So you’ve got your sauna, or you exercise. I like to exercise before I use the sauna because I find that I sweat more readily, more quickly.

Joseph Mercola:  Yeah.

Chris Kresser:  If we’re splitting hairs here.

Joseph Mercola:  No, no, no, no. Ideally, in my case I see a personal trainer and I go to his studio, so it’s pragmatically impractical for me to do that.

Chris Kresser:  Right, right.

Joseph Mercola:  So I do a little bit of different exercise. I’ll do bodyweight exercises and maybe go on my elliptical. But my strength training is after it.

Chris Kresser:  Yeah, and we’re talking about the last few percent here in terms of optimization.

Joseph Mercola:  Yeah.

Eat at Your Normal Time on Refeed Days

Chris Kresser:  You’ll still get a huge benefit if you’re not able to sequence it in the perfect way that we’re talking about. But I know my listeners are really into optimizing as much as possible. So I like to at least lay it out there. So, yeah, then you do your refeed that day and you’re feeling like a million bucks. When you do the refeeds, and even just the compressed six- to eight-hour window in general, I know I get a lot of questions about this from patients, how do you approach it? Do you eat just a couple meals, typically? Or do you eat more than a couple meals during that period? What’s your personal approach?

Joseph Mercola:  Well, it’s not much different than my normal day except I eat more food. So instead of having two eggs in my salad, I have three eggs.

Chris Kresser:  Right.

Joseph Mercola:  And instead of having vegan protein in my smoothie, I switch over to whey concentrate. So I have a lot more branched chain amino acids. I change the ratio of those things around. And it’s the sequencing and the timing, the cycling that is so important, and it’s so massively overlooked. If you don’t understand and you get the timing off, you’re going to sabotage most of your benefits.

Chris Kresser:  Yeah. So you’re basically eating, sitting down and eating the same number of times, you’re just adding some more calories and you’re also switching maybe the type and the amount of protein and carbs.

Joseph Mercola:  Yeah, and if you’re going to eat later, that would be the day to eat later. Now, let me caution you, especially if you have an Oura ring, and you probably know this already if you do, that on that day that you’re strengthening and you’re really pushing it, your readiness score is going to go down the next day. Maybe by 10 or 20 points. Typically 20 points.

Chris Kresser:  Yeah, yeah.

Joseph Mercola:  So don’t be surprised. That’s good.

Chris Kresser:  That’s fine, that’s part of the normal cycling in and out.

Joseph Mercola:  Yeah.

Chris Kresser:  That’s the cycle of catabolism. We never defined these terms, but let me just do this, this process of breakdown, which is a necessary component of life. And then anabolism is repair and regrowth. So it’s just breakdown and cycling between catabolism and anabolism that we’re going for in this protocol. So it shouldn’t be alarming that you see the readiness score drop. Because that’s just part of that cycle.

Joseph Mercola:  Yeah, and what we’re doing with this is, as you mentioned right in the beginning, we’re replicating ancestral patterns which has just essentially been abandoned by the typical diet.

Chris Kresser:  Absolutely. Well, I’m really excited about this strategy. We’ve actually already started using it in the clinic with patients.

Joseph Mercola:  Yahoo!

Chris Kresser:  And are having some good results. So we typed up a whole thing and directing them to your book and your cookbook. And then we, it’s pretty close. That’s why I was so excited when I saw your book, it’s very close to what I was already doing. But I really like how you kind of systematized it. And the patients are finding it really easy to follow and they’re getting some, I think, some really good results. So I’m excited about the book. It’s called KetoFast. And then there’s also, you mentioned the cookbook. When is KetoFast out and then when is the KetoFast Cookbook out?

Joseph Mercola:  KetoFast comes out, I believe, April 30th and the cookbook will be out shortly after that, within a week or two, I think.

Chris Kresser:  Awesome. Yeah, and the cookbook is super helpful too because I think this will be a little bit of a new approach for people in just getting a sense of what they can be eating during these various phases is really helpful.

Joseph Mercola:  Well, let me just tell you how delighted I am to hear your endorsement for this process because myself personally and most of our staff have enormous respect for your clinical wisdom and judgment and your ability to articulate these things. And the fact that we sort of paralleled on the same conclusion is just remarkably reaffirming.

Chris Kresser:  Yeah, I love that too. And I’m an early adopter, as I know you are. You’re probably the earliest of the early adopters. So I have great appreciation for all the work you’ve done and the way you’ve moved the conversation forward over and over again on many of these different topics. So thanks for putting this out there.

The book is KetoFast and then the KetoFast Cookbook. Highly recommend it. It’s really the best way that I’ve seen so far of safely and effectively implementing fasting and ketogenic diet. And avoiding some of the pretty significant risks and downsides to ongoing ketogenic dieting and water fasting. So definitely check it out, and, Joe, thank you so much for coming on the show. I really enjoyed our chat. And what’s next for you at this point?

Joseph Mercola:  Well, I interestingly listened to an interview that Tim Ferriss did with Peter Drucker. Not Peter Drucker, Jim Collins.

Chris Kresser:  Right.

Joseph Mercola:  You’ve probably heard, but his mentor was Peter Drucker.

Chris Kresser:  Yeah.

Joseph Mercola:  And I was surprised to find out that Peter, who’s really one of the icons in the business world, wrote two-thirds of his book after the age of 65.

Chris Kresser:  Ah, interesting.

Joseph Mercola:  So that was a real inspiration to me because I hit 65 this year. And an affirmation that I really do enjoy writing and I’ve got this really good, I’ve got to share this RSS feed with you that you can get to PubMed.

Chris Kresser:  Yeah.

Joseph Mercola:  So I’ve reviewed about 2,000 articles a year now.

Chris Kresser:  Yeah.

Joseph Mercola:  Not the abstracts, but the actual articles.

Chris Kresser:  Yeah.

Joseph Mercola:  So I’m just writing books. My next one is EMF. That should be hopefully out either later this year or early next year. And then one on longevity, which is probably five books, I think.

Chris Kresser:  Yeah, yeah. It’s a big topic that’s for sure. Well, great, well, we’ll look forward to the next one and have a wonderful weekend. Pleasure to talk to you.

Joseph Mercola:  All right, thanks.

Chris Kresser:  All right. Great.

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  1. Hi Chris/Dr Mercola,

    Does MCT oil interfere with autophagy? I was led to believe it does not but some of the comments made in the interview seem to suggest otherwise.

  2. Hi Chris,
    I’ve tried intermittent fasting again & again without success. The longest I’ve managed to go is about 14 hours and then I start feeling hangry and light-headed despite following a low carb diet for over a year. However, I am taking 3 different meds for Bipolar – could this medication be interfering with my ability to fast?