The Benefits of Intermittent Fasting and How to Customize it For You with Dr. David Jockers

Content By: Ari Whitten & Dr. David Jockers

In this episode, I am speaking with Dr. David Jockers – who is a doctor of natural medicine, a world-renowned expert on ketosis, fasting, inflammation, and functional nutrition, and runs one of the most popular natural health websites in as well as hosting the popular Dr. Jockers Functional Nutrition podcast.

Table of Contents

In this podcast, Dr. Jockers and I discuss: 

  • What is intermittent fasting?                               
  • Intermittent Fasting vs. calorie-restricted diet 
  • The role of insulin in the body 
  • Why burning fat is healthier than burning sugar
  • How long should I fast? (Tips for the fit active person, the sedentary overweight person, and the menstruating mother.)

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Ari: Hey there. This is Ari. Welcome back to the Energy Blueprint Podcast. With me now is my friend, Dr. David Jockers, who is a doctor of natural medicine. He runs one of the most popular natural health websites, which is, which is gotten over 1 million monthly visitors. His work has been seen on popular media such as the Doctor Oz Show, Hallmark Home, and Family.

Dr. Jockers is the author of the best-selling book, the Keto Metabolic Breakthrough by Victory Belt Publishing and the Fasting Transformation. He’s a world-renowned expert in the area of ketosis fasting information and functional nutrition. He’s also the host of the popular Dr. Jockers Functional Nutrition podcast. He lives in Canton, Georgia with his wife Angel and his twin boys, David and Joshua, and his daughter, Joyful. There’s the new addition that we were just talking about, which is his newborn daughter that’s a month old who is named– What was the name? I don’t know if you told me.

Dr. Jockers: Her name is Shine Caroline.

Ari: Shine Caroline. Wow.

Dr. Jockers: That’s right.

The definition of intermittent fasting

Ari: Nice. I like that. Cool. We are going to be talking all about fasting. First of all, let’s talk about what the heck is intermittent fasting. I want to maybe just add a bit of context here, because I feel that there’s a lot of confusion around this word perhaps, especially among people who have heard the term before. A lot of people confuse and conflate time-restricted feeding with intermittent fasting. I’ve also seen different experts out there to find these terms differently. I’m very curious to hear how you define this.

Dr. Jockers: I think there’s a lot of overlap there. With intermittent fasting, basically, the term is just you’re taking periods of time without eating. That’s basically what that actually means. Ultimately, you can be fasting from a lot of things. You could fast from social media. You could fast from sugar. Things like that. There’s a lot of things you could fast from. For the purpose of our conversation, we’re talking about food in general. Then time-restricted feeding is this idea of compressing our feeding window.

Again, there’s a lot of crossover there. I use those interchangeably. Time-restricted feeding is going to be more so in a 24-hour period. Ultimately, I consider anything over 48 hours of fasting to be a prolonged fasting. The reason for that is after about 48 hours of fasting, you stop producing digestive juices, stomach acid, bile, pancreatic enzymes. There’s a whole additional set of mechanisms that take place whereas if you break your fast at 36 hours, your body was still in– Even though it had reduced its production of these digestive juices, they’re still present.

You’re still producing smaller amounts of those. Therefore, it in this window of like a more of a short fast or intermittent fast as opposed to an extended fast. To me, anything over 48 hours, I consider it an extended fast. Then time-restricted feeding is really in a 24-hour period. Are you compartmentalizing or compressing your eating window? You might eat in a six-hour eating window from let’s say 12:00 PM to 6:00 PM. That’s your eating window and then based on that you have an 18-hour window where you’re not eating you’re fasting from 6:00 PM to 12:00 PM the next day. That’s how I use those terms.

Ari: Would you classify that, the example that you just gave as intermittent fasting or as time-restricted feeding?

Dr. Jockers: Really both. I don’t have a problem with somebody saying, “Okay, I’m intermittent fasting and I’m doing an 18-6, or a 16-8, or if they say I do time-restricted feeding 18-6, 16-8.” I don’t have a problem with using either one of those terms. I think they’re both accurate terms.

Ari: Where do you think a good threshold could be to distinguish those two? You know what I mean? Would it be like let’s say six-hour or a four-hour feeding window? You could classify as okay, that’s intermittent fasting whereas a 10-hour feeding window is just normal daily life not technically intermittent fasting. You’re just eating with an 8 or 10 hours feeding window each day.

Dr. Jockers: Well, I think it depends on what your goals are and what you’re trying to accomplish. If you’re eating in a 10-hour eating window, I still call it– In my book, I talk about different types of fast. We talk about a simple fast which is a 12-hour, overnight fast which is really more mindfulness. It’s really easy process to eat in a 12-hour eating window and fast 12 hours overnight. It’s actually very easy, but for some people, they’re mindlessly eating. At night, they’re snacking on something before they go to bed, or maybe they’ve been trained this way in order to put on muscle.

I know, for me, many years ago as a personal trainer, and I thought I had to have big protein shake before I went to bed, and then wake up in the morning, eat first thing in the morning, so we start out with a mindfulness practice, which we call a simple fast. Could you call that just time-restricted feeding? Call it what you want, you know what I mean? 14 hours, I call it the brunch fast. It’s like you’re pushing out your breakfast a little bit like your morning meal a little bit further and you’re focusing on hydration in the morning.

Then you get into that 16:8 which is really popular approach.

By that point, your body starts really dipping into fat stores. You start to break down the body fat and of course, it depends. It’s always individualized because if you have high insulin if you’re very insulin resistant, you’re going to struggle to burn fat until you get your insulin levels down and more sensitive. However, if you’re following that 16:8 over time, and your body is adapting to that, you’re going to start burning fat for fuel.

Then once you get into the 18-hour, you’re starting to ramp up some autophagy, and then if you can push it– What I really think would be a great goal for vast majority of our society is for everybody unless you’re a pregnant woman, nursing a newborn like my wife is or high-level athlete in season, or possibly a type 1 diabetic or young child.

Doing something like a 20 to 24-hour fast one day every single week I think is one of the best things you can do to improve your metabolic flexibility to where your body is good at burning fat and sugar for fuel, good at producing ketones, running off ketones and also ramping up intracellular healing this process of autophagy which we can go on to further. Now, what you want to call those things, I don’t know the actual definitions of time-restricted feeding, intermittent fasting. I think that these things are very interchangeable as far as the terminology we use. That’s my thought on it.

Ari: I think part of the fuzziness is that people use the terms in different ways. I personally think something may be the cutoff, being below six hours maybe four hours a day might be reasonable thing. Or to say, you do a prolonged fast of let’s say a 20 or 24-hour fast or a 36-hour fast once or twice a week. I think that would clearly be intermittent fasting rather than time-restricted feeding. To me, I think somewhere in there makes sense to cut it off but ultimately it’s just semantics.

Dr. Jockers: I think time-restricted feeding definitely is within a 24-hour window. What are you looking at? Where you eating your meals in that 24-hour window? You what I mean? Whereas intermittent fasting can extend beyond that.

Ari: Exactly. How did you get started? What was catalyst for becoming interested in fasting and experimenting with it?

Dr. Jockers: Well, like I mentioned, I was a personal trainer in my early 20s and, I was eating six meals a day. I took a nutrition class and I counted how to count up all my calories. It was 50,500 calories a day because I thought that’s what I needed to do. I’m an ectomorph body type so thin shoulders. I’m a thinner body type and of course, when you’re a personal trainer, you want to look jacked. You want to look big and strong like you’re. Anyways, I was trying to do that. I was lifting heavy and trying to put on all this muscle mass and I always had digestive issues but it really caught up to me in my early 20s.

I developed irritable bowel and I actually got to the point where I lost 30 pounds of body muscle. Even though I was trying to exercise, trying to eat I would have intense cramping, bloating in my gut and had developed orthostatic hypotension. I go from sitting to standing, I feel super dizzy. This is around the time I started graduate school in Chiropractic College, and I picked up a book called The Maker’s Diet by a guy who’s now a friend of mine, Jordan Rubin. He was talking all about diet changes, grass-fed, organic animal products, sprouted grains, this kind of stuff. Another friend of mine turned me on to Dr. Mercola. I started reading his stuff. This was back in 2005.

Ari: It’s like I could literally transplant my own story in there apart from the irritable bowel syndrome, that’s identical to how I went from six meals a day to experimenting with fasting as well.

Dr. Jockers: Yes, exactly. Anyways, I started making diet changes, and I was actually a vegetarian in 2004. For a few years, I was a vegetarian, but I was eating soy burgers and all this kind of stuff, and I would eat fish, but it was one of those lacto, what do you call it? Pescatarian type approaches. Anyways, I started eating grass-fed meats, I started reducing the amount of grains and the overall amount of carbs. This is before anybody was talking about the paleo diet. We just called it the healing diet. In fact, another doctor that I was a part of an association with was Dr. Dan Pompa, I don’t know if you’re familiar with him. He was using this approach called the Cellular Healing Diet.

I pretty much took my knowledge from reading The Maker’s Diet, reading a lot of Dr. Mercola’s work, Udo Erasmus’ Fats That Heal Fats That Kill, along with what Dr. Pompa was teaching, and it made a huge difference. I was gaining weight, and I was feeling significantly better, but I still was struggling with a lot of fatigue, and brain fog. I still had very low blood pressure.

I was taking visceral physiology classes, and labs and things like that. We’d take our blood pressure every day, because we’re medical students, and my blood pressure was like 90 over 60. Most people, if your blood pressure is 90 over 60, and you’re in your doctor’s office, they’re going to be like, that’s a great blood pressure. You have such a low blood pressure.

Problem is when your blood pressure is that low, you have trouble getting blood up into your brain, so you don’t think sharply. My hands, my feet were always cold. You actually need a certain level of pressure, like the pressure’s good, gets blood flow into the deep extremities into your brain so you could think sharp and quick. I was dealing with all this, and then I just started noticing and it was part of just becoming more fat-adapted because I was eating a low carb diet.

I noticed that, and I was taking 7:00 AM classes in graduate school, so I would get up and sometimes I didn’t have a whole lot of time to eat, because I was studying for a test or whatever it was, and so I would just drink a whole lot of water. In fact, I would carry around like a gallon water jug with me to classes. I noticed if I just drank a lot of water in the mornings, I felt significantly better. I had never heard the term timer-restricted feeding, intermittent fasting, or anything like that. In fact, I started gaining more weight back. In fact, I got to my peak level of fitness, I was extremely strong.

I would fast until roughly about three o’clock in the afternoon, and I would eat between three and seven or eight. I actually didn’t get hungry until about three o’clock and all of a sudden I got ravenous. I was telling my friends who were like, what are you doing? They saw me gaining weight, I was getting significantly stronger, and I was like, I think it’s the water.

I was drinking a gallon of water a day and I thought oh, it’s the water there. It’s increasing my sarcomeres, creating just better myofibrillar contractions. I was trying to come up with all these physiological explanations. It wasn’t until later that I realized, oh, it’s actually the intermittent fasting enhancing my mitochondrial function. My mitochondria, my muscles, and the cells in my body were functioning significantly better. I was able to produce more energy, the hydration was a good thing, but certainly wasn’t the main factor in why I was able to do that.

I got my brain back, got my body back, and I’ve been intermittent fasting ever since 2005, and that’s made a huge difference on my life and my health, and then I’ve worked with many different clients over the years, and seen tremendous results with them using it.

Intermittent fasting vs. low calories

Ari: Excellent. Okay, so I want to dig into some of the controversy around intermittent fasting. The way that I see it, and that I’ve looked at a lot of literature on this, I don’t want to say all but probably close to all of the studies on this. I’ve also seen it debated in different scientific circles. What I see is two camps.

One is the fasting has all these amazing benefits camp, and the other camp like a lot of for example, “evidence-based fitness circles”, they will say, the studies that compare intermittent fasting approaches to equivalent calorie diets where people eat three or four times a day, but the exact same amount of calories as the intermittent fasting group had essentially the same weight loss, body composition changes, and therefore, there’s no real magic to intermittent fasting. It’s just the benefits of low-calorie eating. What, in your opinion, are the most compelling benefits of intermittent fasting versus eating equivalently low calories, but in a more typical eating pattern of a few meals per day?

Dr. Jockers: That’s a fantastic question. A lot of people do practice intermittent fasting for fat loss, and weight management. For me personally, I’ve never done that. In fact, I’ve never in my life ever wanted to lose weight. I’ve always wanted to actually put on weight. I’m somebody who practices intermittent fasting, which if you had said this, to me 20 years ago, 15, right before I started doing intermittent fasting, I would have said, that’s crazy, I would never do that. The reality is that fasting offers so many more benefits than just fat burning, although fat burning is an important thing. One thing it does, it helps reduce your insulin load.

If we’re constantly eating, every time we eat, even if we’re eating, a stick of butter, we’re going to produce some level of insulin. Some foods are more insulinogenic than others, meaning that we produce more insulin when we eat them than other foods. Insulin is a superhero hormone, It takes sugar out of the bloodstream puts it into the cells. If we have high blood sugar, we get advanced glycation end products. These things are like shrapnel going through our bloodstream, destroy our kidneys, or our liver or our nerves, all kinds of stuff like that.

Insulin is an amazing hormone. We need a good amount of insulin. We need to be able to produce it, but we want to produce the right amount, and not too often throughout the day. That’s really the key. When we are constantly eating every few hours, we’re constantly stoking insulin. When we do that, we get a higher amount of insulin load throughout the day. There’s only so much insulin we’re going to be able to produce in a certain period of time. If we have a whole bunch of calories in one hour, we’re only going to be able to produce a certain amount of insulin in that one hour.

However, if we’re eating the same amount of calories that we would eat in that one hour, but in three meals, every three hours, we’re actually going to produce roughly somewhere around 20% more insulin when we do that, and so our overall insulin load goes up. The more that we’re stoking insulin or we have insulin up, insulin is telling the body store fat, it stops the breakdown of fat, stops lipolysis. That’s one thing.

Insulin can also trigger inflammatory gene pathways. We also get an upregulation of inflammation when insulin goes over a certain threshold. For one person, they may be very insulin sensitive, and it may be very hard for them to get over that certain threshold, but for another person eating the same foods, they’re going to shoot up over that threshold a lot faster, and they’re going to get more inflammation in their system. Fasting, by keeping insulin down, by lowering insulin, really reduces overall inflammation, turns on fat burning, and then when insulin’s low, we also get this mechanism of autophagy. Autophagy is really where our body breaks down or damaged cellular organelles.

For example, within the cell, one of the most important structures is the mitochondria. That’s where we produce all the energy in the cell, and so these mitochondria are very susceptible to oxidative damage, or just the process of metabolism. We can eat a great diet, take really good care of ourselves, they’re still going to rust from the inside, so we need to repair them.

When insulin is up, it turns off, or basically, it tells our body we’re not in a place, we’re not in an environment to repair these mitochondria. When insulin comes down, now we can start to repair the mitochondria. We go in, we start breaking down the mitochondria, take those raw materials, utilize them to form new, healthier, stronger, more stress-resilient mitochondria.

That’s extremely important because that makes our body more resilient to stress, more efficient. Those mitochondria are better at burning fat. When the mitochondria oxidize and they rust, and they become inefficient, they become really bad at burning fat, and they can even get to the point where they can only burn glucose, or basically, our cell can only burn glucose because the mitochondria are so damaged, and now we get really bad fatty acid oxidation. I know your listeners know that when we burn fat for fuel, we produce a lot more energy, and fat is a cleaner fuel. We produce less oxidative stress and free radicals when we burn fat for fuel than when we burn sugar.

If we’re stuck in sugar burning mode, then we’re going to produce a lot more oxidative stress, a lot more free radicals, we’re going to damage these mitochondria, all the different intracellular organelles, we’re going to damage them a lot faster when we’re stuck in chronic sugar burning mode as opposed to fat-burning mode. Then on top of that, we also can produce ketones, and the reason why our body will produce ketones is because it’s really hard to get fatty acids across the blood-brain barrier.

Our brain needs a constant source of fuel. For the most part, we’re burning glucose in our brain, but if we are in a period where we’re not consuming food for a good period of time, glucose levels start to go down and if we’re not good at producing, and utilizing ketones as an energy source, we develop hypoglycemic reactions. We’ve all been there, we’re irritable, we’re hungry. We’re hungry and irritable, we have headaches, nausea and this is all related to brain cells dying because they’re not getting the fuel that they need.

Ketones easily, they’re a byproduct of fat metabolism, the liver produces them, they get into the bloodstream, and they can cross through the blood-brain barrier into the brain and the brain cells, once they’re adapted to them, they uptake them and utilize them for energy very effectively. They really thrive on that and they were able to produce a lot of energy, very little oxidative stress, and actually have been shown elevated ketones in our bloodstream have been shown to actually reduce these inflammatory pathways that basically amplify inflammation.

I compare it to like a siren, like an alarm in a city. You might have crime in one area, like let’s say, somebody goes and robs a bank, and we have crime, and just in that one specific location and that’s some level of really localized oxidative stress and inflammation. However, what happens in our body is when there’s massive, let’s say, protests or something like that, they’re not peaceful, all over the city, we turn on an entire alarm system, because our body’s like, “Okay, I don’t want to die from some sort of systemic infection, this could be like a bacteria that’s going to cause meningitis and kill me quickly.

I’m just going to amp up inflammation, bring out all these cytokines to help clean up the environment so this bacteria, or whatever it is, doesn’t kill me quickly.” We get this ramp-up of inflammation, and one of the pathways is called the Neuro Inflammasome in the brain. Ketones have been shown to shut that off. This is a big issue, Inflammasome itself is a great thing, it saves us, if we get massive infections, we know infections have killed more people throughout the history of mankind than anything else, from pneumonia, from meningitis, people when they would be in battle, or whatever it was, it would get flesh wounds, and then it was actually the bacteria that will get into their system and kill them quickly.

Our body created this inflammatory process, that’s a beautiful thing, we just have to be able to shut it off. In our society, we keep doing things that are pouring gasoline on the fire and keeping that going. Fasting allows us to turn that off by getting the ketones up, getting insulin down, turning on self-repair mechanisms and that’s really why I like to do it, I feel amazing from a mental clarity perspective, from an energy perspective, I feel like I’m more resilient to stress practicing this on a regular basis. Then as a side benefit, for somebody that’s looking to lose weight, it can definitely help benefit your weight loss journey.

The most compelling benefits of prolonged fasts

Ari: Got it. Okay, I’m thinking of all the different ways I want to go from here. I want to break this down, to put this on a spectrum between, like, let’s say, time-restricted feeding that have, let’s say, an eight to 10-hour feeding window each day, which means 16 to 14-hour fasting window each day, each night versus there’s also on the other end of the spectrum, you have the people, let’s say, Valter Longo, or those kinds of people that are arguing in favor of prolonged fasting of beyond three days of fasting, that sort of thing.

I’ve seen people make the argument that that kind of prolonged fasting has very unique benefits above and beyond time-restricted feeding or interim, shorter duration, intermittent fasting and after several days and get like activation of stem cells and things of that nature. On the other hand, I’ve seen people also argue that all the benefits you’re talking about, as far as autophagy, mitophagy, to me things of that nature are also these are just the catabolic processes that happen each night while we’re sleeping.

If we have an adequate fasting window each night of 12 to 16 hours each night, then maybe there’s no additional benefits of doing a more prolonged fast. What do you think is the most compelling evidence or line of logic that you can think of that there is some kind of benefit above and beyond the normal nightly fasting window to do a more prolonged fasting?

Dr. Jockers: This is a really great question, Ari. Honestly, I don’t really think that we have enough data to really be able to create a really great differentiation between them. I look at it like a partial fast. I think it’s a really great thing for somebody that has high levels of inflammation, weight to lose, maybe autoimmune conditions, something like that, insulin resistance. It’s great, especially if they’re on medications, because a lot of times, you’re if you’re taking medications, they can cause nausea, vomiting things like that, if you take them on an empty stomach so taking them with a meal can obviously be really effective.

Calorie restriction, in general, for a short period of time, like, for example, a partial fast, just for the listeners, really, the way I define that is less than 40% of your normal caloric load for at least three days. The average person needs about 2000 calories, or at least the average woman average man, I think it’s like 2500, if you’re very active, you might need more than that.

You’re looking at somewhere between 800 calories would be about 40% for a 2000 calorie person. 800 calories or so or less, the fasting-mimicking diet is 1100 calories on day one and 800 calories, day two through five. That’s when you start really getting the results there and you get autophagy because just when you’re consuming that low amount of calories, you’re going to naturally lower your insulin levels. His approach is not like high glycemic foods either. It’s not like you’re eating or 800 calories of Oreos, or something like that, you’re eating foods that tend to be lower glycemic.

That way, you’re getting that insulin suppression so you’re going to activate the autophagy and the stem cells doing that. Now, we haven’t really compared that head to head with a water fast or even like an intermittent fast for 24 hours. Just a water intermittent fast for 24 hours. We haven’t done enough head-to-head comparison and of course, Valter Longo has his own biases, he thinks this is the best approach and clearly, based on his research, it’s showing a lot of positive health benefits. I think it’s a great approach if somebody wants to follow that.

I do think that doing something like– In the fasting world, one of the big mistakes I think people make is this idea that you’ve got to do the same fasting window every single day. When it comes to, for example, that the hardest population to get to become very metabolically flexible, are your young menstruating females who are very active, they do CrossFit, let’s say, and they’re also stressed, they’re a mom, they’ve got a career.

They’ve got all these different stressors, and we don’t want to just increase adding another nutritional stressor, especially if they’re already low in body fat as it is. We can do things where we can split up the fasting, where you may do it every other day, do some an intermittent fast, where you’re pushing the fasting window, I think, 12 hours overnight. Again, unless you’re pregnant or a high-level athlete in season, something along those lines, you have a newborn, I think that is something everybody can practice. Again, you’re not really getting the autophagy, the deep fat-burning benefits, or anything like that, until you push it up into that 16 to 18-hour window, that’s really when you start getting real results.

It’s also a stressor on the body. We might do that three times a week, for example, what I mean? Every other day or two times a week, non-consecutive days, depending on the stress load the person’s dealing with, as a whole. Ultimately, to me, the goal is, let’s create the level of metabolic flexibility to where you can do a 20 to 24-hour water fast, maybe black coffee, or herbal tea if you don’t notice a lot of cravings or anything like that.

I recommend no calories for 20 to 24 hours, at least once a week, depending on your goals. A thin person, if you’re already at your ideal body weight, you really don’t want to do that more than once a week. If you’re looking to lose weight, you might do two days a week of that or something along those lines or alternate-day fasting and that can also be very beneficial. Or you could push it to where you do a 36 or a 40 hour fast once a week just a little bit longer fast to get stay in that high-fat burning zone for a longer period of time.

I think if you’re doing that every single week for a year, you’re going to get rapid amounts of autophagy cellular healing, stem cell development, you’re actually going to start to activate stem cells there too, because, again, your body is trying to create more resilient cells. It says, “Okay, I’ve got this stressor. I need to be more resilient. I need more efficient mitochondria that are better at burning fat because I’m going periods of time where I need to use my own body fat for fuel.”

Your body is just adapting to the stress that you put it under. I think we’re going to get great results. We still need to do a lot more research to really be able to– If we want to determine what is the very best approach to fasting for the wide majority of the population, we need a lot more research.

How to adapt fasting to your lifestyle

Ari: On that note, maybe there isn’t a best approach to fasting for the masses, like for humans in general, but it might be very specific and I’ll give you just a personal example from my own life. Given that I’ve experimented heavily with everything, I think like you, from six meals a day, eating every two hours to eating one meal a day, intermittent and fasting approaches to extended fasting.

As a very physically active person, for example, I was surfing this morning, I’m going to go weight train very soon. When I’ve done intermittent fasting or when I’ve done fasting during the majority of the day, and let’s say eating only one meal dinner at night. If I try to do that where I’m doing two exercise bouts in the same day, performance suffers a lot in an intermittent and fasting context.

If I simply fuel up after one exercise session before the next, it makes a huge difference in my levels and performance in that next exercise hour. On the other hand, for people who are not super physically active, it’s hard to think of something that might be a better stressor to give a lot of those benefits of autophagy and mitophagy and stimulating mitochondria to grow stronger that physically active people get so much of from exercise. It seems like different contexts of humans might have radically different benefit like pros and cons two different kinds of fasting approaches. Do you have any thoughts on that?

Dr. Jockers: I would completely agree. I would say if you’re out and you’re going surfing and we’re all envious that you’re living in Costa Rica on the beach there. You’re going surfing for one hour or two hours, and then you’re weightlifting for 45 minutes an hour. That’s like a high-level athlete. I would put you in that stage of a high level athlete in season. You might take a day off right, of all of that, or just do something light activity. That would be a good time to do a longer fast during that period of time. NBA playoffs are going on right now. I wouldn’t have these guys doing intermittent fasting right now while they’re training doing two hard practices a day or something like that.

The reality is that, yes, it’s going to depend on your activity level. A high-level athlete, like take LeBron James or one of these guys. I would absolutely in the off season, I would at least take a month and have them do some deep fasting just to really get rid of all the dysfunctional muscle cells that have been beaten up by stress. Have the body start really breaking these things down, stimulating stem cells. They’ve got the money and the resources they can go and get stem cells therapy as well, add that in. They can do all these different types of hacks, but in season you wouldn’t want to do that. Exercise is an incredible hormetic stress to boost up.

Mitochondrial function drives down insulin and exercise itself is stimulating massive amounts of autophagy. You have to be able to recover effectively from that. I think that the two can go hand in hand, but it really just depends on your exercise level. For the average person out there, a really great target for high levels of metabolic flexibility. Again, metabolic flexibility is your ability to break down both sugar for fuel and fat for fuel.

You want to be really good, the way you’re burning fat for fuel is you can go 20, 24 hours without food and be able to perform. Do the things you want to do, not have intense hunger and cravings, not feel super irritable, have headaches, and need to lay in bed. If you’re in that place, you’re very metabolically inflexible, but at the same time, you should be able to do a fast like that 20 to 24 hours and then turn around and exercise and actually feel good like I do. For me, I eat lunch on Wednesdays. What I found already is I actually feel better when I do a lunch-to-lunch fast and dinner to dinner. I sleep better that night. I have better heart rate variability on my aura ring. Wednesday night I don’t eat dinner.

I fast until after my workout on Thursday, usually work at around twelve o’clock on Thursday. Then I’ll break my fast at let’s say 1:30 or so. It’s just roughly 23, 24 hours fasted. Honestly, I feel amazing during my workout and when I’m finished with my workout, I’m not even hungry. I feel fantastic. If I wait a while, I’ll definitely get hungry and I would also lose muscle mass because I’m doing a high intensity and heavy weightlifting session, heavy upper body I did today. I do typically eat typically within 30 to 45 minutes after I finished the workout I’ll shower or whatever it is. I take a lot of essential amino acids, have a great protein shake, something along those lines. I feel amazing.

I’m doing this interview just maybe an hour and a half after I broke that, I feel fantastic. That’s a sign of really good metabolic flexibility. If my workout was really weak and I just didn’t feel like I could perform well in that workout, it’s a sign also that my body’s not good at burning sugar for fuel. If I didn’t have the cravings, but I felt mentally clear until I started working out, but then when I started working out, it was like I was fatiguing too fast, my body’s not good at breaking down that glycogen that’s still remaining in there and utilizing that to help fuel me during that intense workout.

Ari: Got it. Let’s take the average person who is eating– Typical American eating something like 13 to 16 hour feeding window each day, almost some kind of food, whether it’s coffee with cream and sugar going in their mouth within 30 minutes or an hour of waking up and then snacking on something, some bit of snacks or dessert foods or something, some treats, almost all the way up till bedtime. How should that person get started moving in the direction of getting all these benefits you’re talking about in implementing intimate and fasting in their life?

Dr. Jockers: First thing is this mindfulness practice of saying, “I’m going to go 12 hours between my last meal of the day and my first meal the next day.” If you finish dinner at 7:00 PM, you just don’t eat anything with calories until 7:00 AM the next day. In the beginning, if you’re used to eating a meal at 10:00 PM, you’re going to feel hungry in the beginning. That’s because it’s a conditioned response. Your brain is conditioned to want to feel– It’s not true hunger, it’s more of like a craving, almost like an emotional hit that you need.

Your body is trained to have this response. If you’re eating at a certain period of time every single day, you’re normally going to feel hungry at that period of time. After roughly three to five days, you can get rid of that signal. What I recommend is getting some herbal tea and just sipping on the herbal tea. Just getting some water into your system will distend your stomach. There’s a hormone called ghrelin. Ghrelin is your hunger hormone. When you’re, there’s nothing in your stomach, you release ghrelin and ghrelin is also again going to be released based on when you condition it to be released. If you’re eating again at the same time every day, you’re going to notice that at the same time.

Drinking some water will help to stand your stomach, something warmer like a warm herbal tea also will help trigger your vagus nerve, which will help with some peristaltic activity will help calm your brain, relax your body. There’s a lot of benefits to having a little bit of herbal tea in the evening and ideally really prioritize sleep. If you’re eating late at night, that itself is going to dramatically affect sleep quality, and that’s going to cause more insulin resistance, leptin resistance, and this continual cycle of craving and eating.

That’s what I would recommend the beginning. Then waiting, 12 hours before your first meal. When you wake up in the morning, all of us are dehydrated when we first wake up. That’s because we’ve been breathing out water vapor all night long. people think dehydration is like always a chronic state. We fluctuate through periods of hydration and dehydration all throughout the day. All of us do.

In the morning, we’re already hydrated. We need to replenish that. I recommend drinking at least eight to 16 ounces of water before you even think about food. You just start hydrating your body. For some people, drinking eight ounces of water, they feel nauseous. There are so not used to doing it. That they’ll feel nauseous. You start slowly and you start building it up. Pretty soon your natural mechanisms and desire for thirst will pick up.

You’ll actually crave the water and the hydration, and you’ll notice that your energy goes up when you hydrate well. Good hydration also helps stimulate the vagus nerve activity, particularly again warm water in the morning like warm lemon water, herbal tea, even coffee, if you tolerate coffee, will help stimulate the vagus nerve, which will stimulate peristaltic activity. You really want to have good bowel movements in the morning, your large intestine is most active between 6:00 Am and 9:00 Am, you want to have at least one to two really good bowel movements between that period of time, or at least in the first hour to two hours of waking up.

That will make it so much easier to fast because if you’ve got feces sitting in your system that’s not moving, it’s rotting, it’s putrifying, you’re releasing all these endotoxins. Those endotoxins themselves will stimulate more cravings. They’ll cause more damage to your hypothalamus, your hunger center will be affected and you’ll constantly be craving food. You got to get that stuff out of your system. Hydrating well in the morning will help, a little bit of salt can really help as well. Just taking even just like a little bit on your finger, putting it on your tongue, or you can do a quarter teaspoon in your water, and that will help with energy as well. That’s a great thing to do.

Then from there you only eat three meals, you don’t snack, eat three meals in whatever eating window, 10-hour eating window, 12-hour eating window, and just allow yourself to go three to four hours, at least, without eating in that window. That’s the first place to start. Ideally, we’re dialing back some of the carbohydrates, the average individuals eating something like three to 400 grams of carbohydrates a day. We want to dial that down. You might just start by cutting it in half. If you’re eating 300 grams of carbohydrates a day, drop it down to 150 grams of carbohydrates a day and split it up, in fact, actually eating more of them in the evening.

It’s one of the things I go through a lot in my book keto metabolic breakthrough. We talked a little bit about this idea of carb backloading, where we go low carb during the day, so more higher-fat protein foods during the day, and then our evening meal, we have a little bit more carbs because they help increase serotonin production, they can help provide glycogen just in case we are having blood sugar issues, keep us sleeping well overnight. That will also reduce cravings.

I find that when people are eating for example if you have a big smoothie with two cups of fruit, strawberries, pineapple, all this kind of stuff in the morning, and you’ve got maybe some almond milk in there and protein powder, but very little fat, you’re going to be hungry all day long, you’re going to have monster cravings all day, and that’s an issue. If you have a bowl of oatmeal, now oatmeal will keep you satiated, but it will keep your insulin up for hours afterwards, because it’s got high glycemic load food.

A lot better breakfast would be if you’re going to do the smoothie, put an avocado in there, only do half a cup of berries, good protein powder in there, maybe a coconut oil or something like that. You have the healthy fats, or you can do eggs or something like that. Where you have more a meal, that’s going to stimulate less insulin. Then it’s the same thing with lunch. If you’re going if you feel you tolerate carbohydrates like if you want more carbohydrates, I recommend doing them more in your evening meal.

Even though you tend to be less insulin sensitive in the evening, I think the benefits of keeping things suppressed during the day, keeping your insulin level suppressed during the day reducing the amount of cravings that you have. Then having a little bit more in the evening, which will then also activate more thyroid hormone activation, which will increase also serotonin production will help you get better quality sleep. That good sleep is going to help improve your insulin sensitivity. That’s just my feeling on it. I think that’s a better approach. That’s typically what I’ll have people do to start.

Over time, because they’re doing carbs only one time a day, a higher carb load one time a day, they have suppressed insulin overall compared to where they were on and their body gets better at burning fat for fuel, which gives them more satiety. Then the natural satiety starts kicking in and then I’ll say, “Okay, let’s try really finding a tighter eating window” We have to based around somebody’s schedule and what works best for them, but for most people lunch and dinner tend to be more social.

Fasting in the morning for most people just makes the most sense and we’ll just hydrate during that period of time. Keep hydrating, keep drinking water, herbal teas, things like that. Anytime you feel hungry drink some herbal tea or drink some water, and then see if the hunger goes away. Or if it stays. If you drink an eight-ounce cup of water, and then five minutes later, you’re still hungry, break your fast. Or plan your workout, depending on when you’re working out, we can experiment with fasted exercise as well, and then breaking it after the exercise.

Ari: All that is excellent. On a practical level, let’s take two different people, let’s take someone like me or you, fit young guy doing a lot of physical activity. I guess I’m not that young anymore, I’m still thinking of myself as a young guy. [unintelligible 00:45:45]

Dr. Jockers: [chuclkes]

Ari: Let’s say a mostly sedentary person in their 50s or 60s, who is very overweight and is not particularly physically fit. What does a good weekly schedule and this is what I want to wrap up with, just the practical blueprint for what I think is optimal for these two people in terms of daily feeding window, and also, what would be a good intermittent fasting approach for those two contexts?

Dr. Jockers: I’ll throw in another context as well, which would be like that menstruating female as well. For you and I doing something like a 16-18 hour fast on a daily basis, but when we eat two to three meals in your six to eight-hour eating window, eat well, and especially if you’re very active, have one meal where you’re getting somewhere at least 25 to 50 grams of good quality net carbs on a regular basis.

You might do one day a week maybe, where you go real low carb, but if you’re very active, I would definitely recommend getting at least 50 to 100 grams of net carbs each day in and usually prioritizing them in one main meal tends to work well to load up that glycogen. That’s what I would recommend and then adding in a 20 to 24 hour fast one day a week. There may be one day a week where you just do what we call feasting. Where it’s I’m not even worried about fasting today, I’m just going to eat as much as I want whenever I want. For a lot of people, it’s a good mental break. Doing something along those lines, I think for a fit person is a great strategy.

For the person that is they want to lose 30 pounds, not very active, overweight. That person, we want to get them doing 16 to 18-hour fasts on a regular basis. Also, we want to add in a 24, to maybe even up to a 40 hour fast where they fast from, let’s say, dinner Saturday to lunch on Monday, for example. Then we added one day where we’re having a higher amount of carbohydrates. It really depends on the individual. If their fasting insulin is really high, we might not do that. If their fasting insulin is pretty decent, then we’ll do one day a week where we might go to 100 or 250 grams of carbohydrates, that feasting day to just reactivate certain hormones tell the body, hey, we’re not in a state of scarcity.

We want this diet variation to take place where the body doesn’t feel we’re in this environment where there’s no food around, we want to cycle back and forth between periods of famine and periods where we’re telling the body based on the amount of carbohydrates we’re consuming, that food is plentiful. Insulin is more elevated. We are doing something along those lines.

Now, if the person is doing that, and they’re still struggling, we can experiment with doing very low carb for a longer period of time? See if that helps budge. There’s a lot of different mechanisms here, we can try that. We can also look at, for example, food sensitivities. Sometimes people have, they’re reacting negatively to eggs or coffee or something like that. They’re consuming it every day, even though they’re on a low-carb diet doing fasting, and they’re still not seeing changes. We may have some issues with that.

There’s a couple of other, different hacks that we have to look at when it comes to they may not be sleeping well. We have to optimize sleep habits, all those kinds of factors, but something along those lines is usually a good strategy. For the menstruating female that’s, also to do high-intensity exercise and is also a mom and has a career. We might only do intermittent fasting two days a week, I call it crescendo fasting.

We might do it Monday and Thursday, for example. Ideally, in the beginning on non-exercise days, we’re doing that intermittent fast, and if they feel good with that. By the intermittent fast, I mean up to that 16-hour window, not the 12 or 14. I think that’s a baseline that everybody should be doing on a daily basis. The 12 to 14-hour fast to me is your baseline.

We’re trying to do that again unless you are the sensitive population like a pregnant woman or nursing a newborn or a high-level athlete or possibly a type one diabetic although many of them can do a 12 to 14-hour fast easy. My kids do 12 to 14-hour fast overnight all the time. Anyways, for those women, we’re pushing that 16, maybe even 18-hour fast, but only two days a week non-consecutive days. In the beginning, we’re doing it on non-exercise days.

Now, if they feel good, they say, “Okay, on the 16-hour days, I just feel great. I feel really good.” We’ll do it three days a week now, every other day, and then, if they’re still feeling good with that, let’s try adding an exercise at the end of that fast and see if they’re able to do that. We’re just slowly adding these stressors. We’re not overwhelming the system, but we’re priming the system to become more resilient. That’s ultimately where we want to be.

The person that’s 55 years old and 30 pounds overweight, high insulin, fasting is going to be a great stressor, exercise is going to be a great stressor on that person. As long as we are also sleeping well, trying to keep our stress down, trying to make positive eating changes, things like that, typically, they can handle more of that, but everybody is a little bit unique, but the vast majority of those people can handle a little bit more intense fasting.

Ari: Excellent. Dr. Jockers, this has been great. Thank you so much for coming on the show and sharing your knowledge. I really appreciate it. Really good info on intermittent fasting. I think this is probably the single deepest dive I’ve done on the subject of intermittent fasting. I really enjoyed it. Thank you. I have had, I’m trying to think, I’ve had Dr. Dan Pompa on and I’ve had Valter Longo on and they both have their takes on fasting. Pompa talks a lot about nutrient cycling and things of that nature. Valter Longo talks a lot about the more extended fast. This was a nice filling-in-the-gaps episode. Great stuff. Thank you so much for coming on the show.

Dr. Jockers: Thanks, Ari. It’s been an honor and I love talking about this topic, so thanks for having me.

Show Notes

The definition of intermittent fasting (05:19)
Intermittent fasting vs. low calories (17:37)
The most compelling benefits of prolonged fasts (26:58)
How to adapt fasting to your lifestyle (34:28)

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