Tips to Live By

PODCAST: The Benefits of Intermittent Fasting (Beyond Weight Loss)

May 30, 2023


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Few diets have generated as much buzz as intermittent fasting, a way of eating that involves abstaining from food consumption on a regular schedule. Touted as about when you eat rather than what, it's gained great popularity as a means of weight loss. But its value beyond losing weight may be its promise of a host of other benefits — better heart health, improved cognitive function, blood sugar control, reduced inflammation, to name a few. Can not eating over fixed blocks of time really effect such wholesale improvements? In today's episode, we learn about the metabolic science of intermittent fasting and what it means for your body.

Hosts: Zach Moore, Todd Ackerman (interviewer)

Expert: Dr. Philip Horner, Neuroscientist

Notable topics covered:

  • Intermittent fasting: Is it really just a form of caloric restriction?
  • The benefits of burning ketones (fats) instead of glucose (sugars)
  • The changes that occur in your brain and throughout your body when you fast
  • Spinal cord regeneration: The intermittent fasting research that got neuroscientists interested
  • The evidence that intermittent fasting improves growth and repair states in multiple tissue types
  • 16/8, eat-stop-eat, 5/2: The primary types of intermittent fasting
  • Contrary to the hype, the quality of what you eat when fasting matters
  • Tips for making intermittent fasting successful
  • Who shouldn't take on intermittent fasting
  • How intermittent fasting appears to improve gut bacteria


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Episode Transcript

ZACH: Welcome to On Health with Houston Methodist. I'm Zach Moore. I'm a photographer and editor here, and I've worked in multimedia and television for over 15 years — and I'm also a longtime podcaster.


TODD: I'm Todd Ackerman. I’m a writer/editor who previously covered Science and Medicine for the Houston Chronicle.


ZACH: And Todd, have you eaten anything today?


TODD: Well, you know, it’s afternoon now.


ZACH: So, I would hope so.


TODD: Yeah, so I had breakfast. I had something of an abbreviated lunch.


ZACH: What is an abbreviated lunch? What does that mean?


TODD: Well, I didn’t realize that I didn’t have that much in the refrigerator, so it was like some nuts and yogurt.


ZACH: Okay, that’s sounds very healthy.


TODD: A piece of fruit. Yes.


ZACH: Yeah. Sounds delightful.


TODD: Yes.


ZACH: I sometimes eat that for breakfast.


TODD: Nuts?


ZACH: Yeah.


TODD: Well, that’s good.


ZACH: Well, you know with like yogurt and stuff.


TODD: Yeah, that’s true. Yeah.


ZACH: Overnight oats.


TODD: Yeah. I love overnight oats.


ZACH: Good stuff.


TODD: Yeah.


ZACH: And as interesting as our eating habits may be, Todd, that’s not exactly what we're talking about today.


TODD: Well, it’s a little bit what we’re talking about today. It’s when you eat those things that we’re talking about.


ZACH: True.


TODD: We’re talking about the subject of intermittent fasting, which is one of the most popular diets out there these days.


ZACH: Yeah. When you hear that term it’s one of these weight loss approaches that seems to have popularized itself in the last few years, right Todd?


TODD: Yes. There are many touted benefits for it, but weight loss seems to be its greatest appeal for people. I looked up if I could find anything about its popularity and according to a recent survey by the International Food Information Council, it is the most popular diet these days.


ZACH: Why do you think that is?


TODD: Well, I think one thing that makes this popular is it’s advertised at least as it’s more about when you eat than what you eat. So, I think people go into with the idea they can eat the usual thing and just change the time at which they eat and lose weight as a result.


ZACH: No, that makes sense because when you look at a lot of diets, there’s lot of rules, as there should be if you’re gonna change your habits and you eat, drink, etcetera, and rules are hard to follow. So, they’ll see the more -- just do what you’re already doing at different times, and yeah, I agree. I feel like that’s probably the reason why that is the most – That surprised me. I didn’t know that stat. That it is the most popular diet these days.


TODD: Yeah, so according to thise council, 43% of Americans say they follow a specific diet or eating pattern, which is up from in recent years, and ten of those follow intermittent fasting. Ten percent of those.


ZACH: Wow, okay. Have you ever tried intermittent fasting?


TODD: Well, you know, I actually tried it this week. I made it for a few days, and it seems on the impractical side for me, you know? There’s a number of ways to do this. The most popular which is this time restricted way of typically, it’s called 16:8 which means you don’t eat for 16 hours and then you cram all your eating into eight hours.


ZACH: Okay.


TODD: And I found going without eating for 16 hours fine, but the eight hours, cramming three meals into eight hours seemed kinda difficult to me. And as a long-term strategy --


ZACH: Unsustainable, huh?


TODD: Yeah, it seems sort of socially inhibiting too that you had to wrap up eating by a certain time every night. It also seemed impractical to me because the specific times that you typically do this don’t really jive with my schedules since as we established in an earlier episode, I’m a night owl.


ZACH: Yeah, that does make sense ‘cause you have the 16:8 is the hourly one. But there’s also like the 2:5 or the other variations that’s more of a daily intermittent fasting, correct?


TODD: Yeah, there’s different ways to go at this. The 5:2.


ZACH: 5:2, okay.


TODD: Yes.


ZACH: I have not tried intermittent fasting as you might have guessed.



TODD: That one is actually not what I thought it was at first. That's actually on two days of the week, you only consume a small amount of calories. The one in which you don’t eat on certain days at all is known as the Eat Stop Eat method --


ZACH: Okay.


TODD: And that can be either done like you eat for 24 hours --


ZACH: You eat nonstop for 24 hours.


TODD: I’m sorry. During one 24-hour period --


ZACH: Right.


TODD: You eat your normal, as you would normally, and then during the next period, you don’t eat at all. The next 24-hour period. So, that can be done Eat Stop Eat day to day, or some people do it more of a 5:2 or even a 6:1 in which they eat normal for five or six days a week, and then fast the other day or two.


ZACH: Interesting, interesting. That does seem well, definitely more extreme.


TODD: Fasting every other day seems pretty extreme to me.


ZACH: Did you try that, or did you just try the 16:8?


TODD: I haven’t tried that.


ZACH: Okay.


TODD: I have done liquid fasts or juice fasts, liquid diets for long periods. Took a while to adapt to that but I liked those.


ZACH: And just for clarification when we’re talking about fasting here, is water included in these fasts?


TODD: Yes, you can drink water or even some like coffee or tea some say.


ZACH: But definitely no solid foods?


TODD: Right.


ZACH: Okay.


TODD: Anything with nutrients in it.


ZACH: Gotcha. As we’ve been talking about, weight loss seems to be the number one attractor for people to implement this habit, right, Intermittent fasting? But we’re gonna take a different approach to it in our conversation today. Right Todd?


TODD: Yes. Although weight loss is the big draw, I think it intrigues a lot of researchers because of its metabolic effects and the effects on your brain that it’s touted to have. Evidence is mostly with animals. They’re just starting to do some of the research but there’s a lot of excitement about the things that it might be able to do. Things like clearer thinking, improved mood, live longer, prevent disease processes, or delay disease processes.


ZACH: So, who do we talk about this today, Todd?


TODD: We talked to Dr. Philip Horner who’s a professor of neuroregeneration at the Houston Methodist Research Institute. His interest is not so much in the weight loss area but the effect on the brain.


ZACH: Alright, well, let’s get into it.


[Sound effect signaling beginning of interview]


TODD: Quick question before we really wade into this is why is a neurologist interested in this? I assume it’s pretty different than a dietician’s or nutritionist’s --




TODD: Putting interest in it.


DR. HORNER: Well, I got interested in it from a study that’s, I don’t know, I’m gonna guess it’s like 20 years, maybe more, 25 years ago from a colleague of mine named Dr. Wolfram Tetzlaff. And he did a study in mice, and it was just intermittent fasting in mice who had had a spinal cord injury. And he showed that they had much better outcome from spinal cord injury. And we -- there’s very few things that we have seen that improve outcome from, you know, nervous system trauma, right? There’s very few things. And I think when he first showed that study, we were all kind of skeptical, you know, cause we were all trying to do these very, you know, advanced, putting the advanced technologies on this, trying to regrow the nervous system and putting electronics and so forth in humans, and we’re all still trying to do that. But his data was really shocking. And so, that started to wake up, I think a lot of us in -- who are interested in brain repair that something as simple as this. Now, if you look for, you know, today, you know, in people who have brain injury, you know, we’re still working on giving them a ketogenic diet. So, we know that diet’s really important actually from the outcome from stroke, from head injury, from spinal cord injury, so that early period. So, we can kind of high jack some of these mechanisms to protect those tissues. So, that’s where my interest came in and of course I think a lot of colleagues started trying the intermittent fasting to sort of be convinced that maybe this is good for brain function.


TODD: So, before we go any further, can we define things a bit? What exactly is intermittent fasting?


DR. HORNER: Well, intermittent fasting -- and we should probably define it and also maybe what the goal is too, right? So, intermittent fasting is a form of caloric restriction during a certain amount of time, right? So, a classic intermittent fasting is just every other day not eating. So, you eat for one day whatever you want, and then on opposition days, you don’t eat. And just kinda getting at the meat of this what your goal is or can be at least scientifically one of the goals of intermittent fasting is to achieve a state where you change the metabolism of your body, so you’re trying to get your body to change from burning glucose, which is a classic, you know, that’s the sugars we eat, right, carbohydrates. You get it to, not completely switch but to begin to have a larger proportion of the amount of fats to be burned, right, so ketones, in particular. And that’s different probably for everybody, meaning that maybe if I fasted for 18 hours, I might get into some state where I have, you know, I’m starting to burn fats more, but maybe you wouldn’t, maybe you would require 24 hours or more, right? So, I think it’s that maybe a million dollars answer to your nickel question. But I think it’s important to kind of say that that’s what it is. It’s a form of caloric restriction with different patterns that people administer or try, but the goal is really to kinda, you know, sorta transform the metabolic state of your body to switch between these two fuels to some degree.


TODD: You mentioned that 24 hours on, 24 hours off is kind of the classic way, but it seems like the popular way with people who are adopting this now is the 16:8.


DR. HORNER: That's right.


TODD: Is that any different?


DR. HORNER: I don’t -- Is it different? It is different in the sense the time in which you’re burning fats is gonna be a little bit shorter than if you do a full, you know, complete day, right, day on, day off. And so, the idea there is that you can eat whatever you want in this short period of time, just sort of gorge yourself for five hours, and then don’t eat between then. So, I think the only difference might be, and again, this is probably dependent upon the person, is that your sort of ketonic state or the state when you’re burning less sugar, more fatty acids, then that could be longer depending upon on how you fast, right? And then, I would say that there is some data to suggest that even short amounts, right, of getting into that state, short periods of time, is beneficial. Is it important to have longer periods of time? I don’t think we know that yet.


TODD: But are people even doing the one day on one day off? I know they do mice studies with that, but is that sustainable for the average person to eat one day and not the next?


DR. HORNER: Again, it’s gonna depend upon certain things, right? So, depend upon your health status and your diet that you use on the alternate days. So, just to con -- sort of declarative there. But yes, it’s certainly sustainable as long as you eat enough calories on your off day. I mean, there are people who go on fasting for quite a bit longer than that, right, and that can be healthy if it’s done right, you know, in the right way, alright? If you plan your caloric intake accordingly and also the quality of what you eat.


TODD: Right. So, you mentioned kinda eating whatever you want then -- I’m a little surprised at the seeming medical acceptance of a diet based on the idea that it’s more about when you eat than what you eat. Is that a misperception? I mean, does the medical community kind of accept this to the extent that they do based on the idea that they assume you’re eating fairly healthy anyway, or is it really a matter of when versus what?


DR. HORNER: That’s probably a misconception, right, because I think when you’re not fasting, if you’re not eating a healthy diet, you’re not gonna get all the benefits. And in fact, we should probably mention that there is also evidence that you kind of get into this more ketogenic state, this fat burning state, in some -- there’s some evidence that just by changing your diet, right, you can do that, by dramatically decreasing the amount of sugar you eat, right? So, there is that. And also, there’s some studies that show that you can even achieve that state just by adding some exercise. And that’s why I kept saying sort of a complicated answer to your question. So, maybe a short term fast, but you’re also exercising, you may get into that state much quicker than someone who isn’t. And then -- And vice versa, if you’re on your off day, if you’re eating candy bars and whatever, you know, and not nutritional food then you’re sort of probably deleting a lot of those benefits that you might get.


TODD: But you are -- The premise of the diet is that you are getting less calories by doing this.


DR. HORNER: I don’t think so. Again, I don’t think the goal is -- So, you can get -- alright. So, you can get to a lot what are published benefits. You can get to the published benefits in my, this is in my look at the literature. You know, there’s a couple thousand articles on this, you know, so, in pub med. If you look at it, I think you could -- I think the argument could be made safely that you could get to that goal with intermittent fasting and that would be not caloric restriction, meaning you could make up the calories during your nonfasted state. So, you could eat as much as you would normally eat, right, in a 48-hour period even if you did every other day fasting. You can get to that state and then, you know, there are also studies suggesting if you just did general caloric restriction, so that would be doesn’t matter when you eat, but you just reduce the total amount of calories by a significant amount, if you do that, you can also evidently enter this state. So, now, the question -- You’re asking, are you expected to be eating fewer calories? I think that the general assumption is that if you do fasting, you end up eating less, right, and it’s just because you have less time to eat, and you’re still gonna have that satiety signal, so like you’re not only eating within five hours. You know, you may think you’re gonna eat a lot, you know, with everything you possibly can, but your stomach, your body’s still gonna send those signals back to you as satiety signal. So, you’re gonna probably, you know, sort of default to eating less calories, right, just naturally. Again, is that the major health benefit? It's probably part of it, but it seems like the real benefit, at least scientifically, seems to be more geared to this switch in the metabolic state. So, you’re reaping benefits in the fasted state, not just so much just in being calorically restricted.


TODD: So, what changes occur in your body when you fast?


DR. HORNER: If you fast enough, right, for a long enough time, your body starts to use -- starts to burn more fat. It mobilizes fats, particular ketone or ketone bodies and there are different products of those. You start to burn those. So, why is that interesting and then what happens after that I guess? So, you’re normally burning  mostly glucose, a little bit of these ketones, and then when you switch to burning  more of these ketones, so it turns out that ketones are much -- you get a lot more energy. So, if you compare like one sugar with one ketone, you can get a lot more energy from one ketone. So, they’re much more energetic, and then this is particularly true for the brain. So, the brain likes to burn ketones. So, it likes to be in that state because that’s the most efficient fuel the brain has. And so, what happens is that during that -- the burning of that fuel, you see a lot of different pathways in the body get upregulated. So, you’re gonna see things like growth signals, cell growth signals increase and improve. Signals that promote the removal of damaged cells get upregulated. in the brain, you know, and again, that’s just my expertise and studies that I’m excited about. Now, these studies are primarily in rodents, although, there is some studies in humans. In rodents, we see that there’s an increase in the growth factors that your body makes for your brain. So, these, you know, factors that make your nerve cells get excited and grow, right? And actually, there’s a very good correlation with that growth signal and improvement in cognitive functions. So, mice and rats do better in learning and memory tests when you put ‘em into intermittent fasting or caloric restriction. And there’s even studies, a pretty large cohort of studies now in humans who have early Alzheimer’s disease, and if you go into that state, it appears that a similar thing happens in human brain, meaning that -- and partly because I have this very efficient fuel that you’re putting into the brain, and you’re also decreasing that oxidative state, right, so the highly energetic state with the glucose which has some byproducts that are somewhat damaging  to cells. So, you --when you do that and when you see that in humans with Alzheimer’s disease, you see improvement in cognitive function. You see improvement in learning and memory as well. So, those are just some of the processes that happen. Again, I’m not a nutritionist or you know, I don’t really think a lot about the cardiovascular system as much as an expert would. There’s also very good indicators it’s good for the cardiovascular system. You see improvement in things like new blood vessel growth is encouraged in that state. So, overall, you’re seeing an improvement in growth state and a repair state in multiple, you know, tissues of your body.


[Music plays to signal a brief interjection in the interview]


ZACH: Dr. Horner touched on some of the dietary aspects of intermittent fasting, so we took a look at what the science says about the number one reason most people take up the timed eating plan, weight loss. The answer is, it depends on the study. For a time, the evidence seemed to suggest intermittent fasting was a very powerful weight loss tool. One review study found that the diet can cause three to eight percent weight loss over three to 24 weeks. Considered significant compared to most weight loss studies. The study also found people lost four to seven percent of their waist circumference indicating a significant loss of harmful belly fat that builds up around your organs and causes disease. Another systemic review of studies also found that intermittent fasting was effective for weight loss with a typical loss of seven to 11 pounds over ten weeks. But some researchers in the field question the significance of the reviews because there was so much variability in the studies. Many were small, of short duration, and without control groups. Last year, a more rigorous study found participants following intermittent fasting lost no more weight than those who ate at any time. The study, published in the New England Journal of Medicine, followed 139 significantly overweight people, who, to ensure compliance, kept food diaries and were required to photograph every bit of food they ate. People were divided into two categories, those who only ate between 8:00 AM and 4:00 PM, and those who consumed the same number of calories any time during the day. Both ate a low calorie diet. “The bottom line,” said one researcher was that quote, “There was no benefit to eating in a narrow window.” In one sense, that's not exactly true. Those confined to eating in the eight hour window did lose an average of 14 to 18 pounds. It's just that the other group did too.

[Music plays to signal the resumption of the interview]



TODD: It seems like I'm seeing contradictory findings in studies, I guess, not surprisingly, but mostly positive, I guess. But for instance, I saw one, a recent Mount Sinai study that it compromises the immune system, make it harder to fight off infections, can lead to cancer, cardiovascular disease. Any reaction to studies like that?


DR. HORNER: I'll go with the old adage, everything in moderation. So, you know, I think that's true of everything in life. So, when you think about the scales, so you're tipping the scales a bit. So, when you -- there's good evidence that when you do intermittent fasting, when you get into a ketogenic state that you have a reduction, in fact, I think there are studies in humans, there's a reduction in the circulating inflammatory signals that are in our blood. So, inflammatory signals like, yeah, aisle six. So, there are these inflammatory factors that are circulating. And so, you decrease those when you're in this state. Now, that might be good if you have arthritis, and there's studies that suggest that's good. It's also good if you have some brain inflammation. Maybe you have epilepsy, right? It actually can decrease --there's quite strong studies even in humans that show that it can decrease the chances of having a seizure. But what's the, you know, on the other end of the scale, what happens if you lower some of that sort of immune activation? You've changed that immune activation, say. Well, then maybe you're not as good at surveillance of cancer cells in your body. Or if you have an active infection, maybe that also, right? It's kind of when you may want your immune system to be in that highly activated state, right?

TODD: So, how much is this being studied, like, especially in humans as opposed to mice?

DR. HORNER: Yeah, I think these studies are hard to do. I think that they're -- you're starting to see more and more. You know, I've seen -- you know, I'm a neuroscientist, so I look more for you know, studies having to do with brain aging, and injury and you know, regeneration. And there's quite a bit there. Most of that's in rodents, right? So, the predominance of the data's in rodents and there's some coming out in humans. And the reason I think, this is becoming a very exciting topic. You know, you're gonna see more and more of it in clinical tests and clinical trials, right? But I think it's also just kind of going back to where we started, you know, the human population is necessarily, you know, a very diverse population in terms of their genetics and their metabolic state and their, you know, what they eat and whether they exercise and all of these things, whether they have precon -- you know, preexisting conditions and so forth. So, to see -- I don't see like really big, you know, large cohort human studies yet that are focused on, you know, you mentioned cancer, that cancer study, those studies are still relatively small, I think. So, we really have a lot of work to do to figure out in the human population what the impact is.


TODD: I've heard the term metabolic flexibility. What is that?


DR. HORNER: When we think about metabolic flexibility, we talk about it in neuroscience as sort of hijacking the brain, but it's true at the systems level, right, throughout your whole body. If you decrease your insulin sensitivity at a similar amount of insulin, your body is able to liberate fat for consumption. So, being flexible means that you're not really, you know, fully tied to burning glucose all the time and being really reliant on insulin, right? So, in insulin, if you can adapt the way your cells respond to a particular level of insulin and how insulin levels change when you eat, that's sort of creating this flexibility. And what we're trying to avoid, obviously, you know how -- the classic when you eat something and you feel great, maybe a sugary meal and you feel great for, you know, half hour and you're like, “Wow, that was great,” and then you crash, and you need a nap. So, that's the inflexible person, right, who can't switch over or can't, you know, adequately transition from a state of burning carbohydrates to adding in these other components. And I think if you, again, this not necessarily my area, but I think if you look at in general health as generally perceived that if you, or if I were to measure your ketone levels and your blood glucose levels, if I could check you out and see that you're not always burning sugar, but you're also burning ketones, you're, you're kind of a -- you're flexible that way, that's a sign generally of overall better health, right? So, that is a good sign. And I think that that’s when we talk about this flexibility, that's what we're talking about, your ability to shift, I think, between these states, and it helps prevent the crash, right? And when you, right, when sugars are harder to mean at that constant level, if you don't have that metabolic flexibility.


[Music plays to signal a brief interjection in the interview]

TODD: After the break, more with Dr. Horner

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TODD: And now we're back with Dr. Horner.

DR HORNER: I can count the number of times I've tried to fast on one hand. So, in thinking about it from a personal experience, it seems that you go through this period, right, where you're really hungry and you think, “I don't want to do this.” And then it just -- that just passes, you know, and that passes after certain amount of time for different people. And then you get into this state where you almost don't want to eat. You don't really feel hungry, you feel good. And a lot of people think that's where like the mental clarity and, you know, aspects of this happen. And so, what's too much? Well, I don't know, but probably, you know, you're gonna have a limit right, where your body runs in that state. And maybe for different people it's, you know, different periods of time. I can't give you a prescription of what that might be, but maybe an indicator is probably your energy level, right, at some point. ‘Cause I think you get into a good state, I think a lot of people don't realize it. When you start a fast, once you get past that hunger phase, you usually get into a pretty good state where you feel good. So, maybe the -- you don't want to push that too long. I don't know what that time is for most people.


TODD: Yeah, I've never done intermittent fasting, but I did a like four-day juice fast. And then I was on an all liquid diet after surgery for 22 days.


TODD: And one thing I was struck by, early on, it was very difficult for me, and then I hit that sweet spot that you mentioned. But with intermittent fasting, can you settle in that well? I mean it seems like you're so up and down that it would be hard to kind of hit that point at some point.

DR. HORNER: Yeah, that's a good question. And I have -- I've never done intermittent fasting. So, I have done like a two-day fast, three-day fast. And in those states, just exactly what you said. In the beginning, I'm like, “What am I doing? This is -- I'm so uncomfortable. I need to eat.” And then about at, really honestly at about 24 hours, I was kinda like, I didn't care if I ate for a while. I felt really good, and it was almost like I could be really choosy. “What am I gonna eat? It doesn't matter to me. I feel really good.” So, intermittent fasting, I don't know if people really get that state. It almost seems -- cause this is just personal, right? This is my personal opinion. But the reason I haven't done intermittent fasting partly is because I like to work out, right? So, I want fuel. So, when I work out, I try to work out six days a week. So, I don't want a period when I don't have some fuel I can put in there. But I also think that when you're doing the intermittent fasting, it seems to me that you gotta go through that hard period, and you probably have a pretty short period where you're really in that, what I think is a good state, right? So, I don't know. I mean it's probably different for different people. So -- and I can't speak to it not having done it. But what - actually, but you know, you're bringing up an important point. You know, everyone's doing, like you said, this is really popular right now. Why is it? I don't think there's a scientific reason why that is, to be honest with you. If you look at studies, most studies -- so like if you look at a lot of the animal studies that are done, most of those are pretty significant reductions, like enforcing the eating window to be two hours, right? So that's like really almost like a 24 hour fast. And in -- so is that as good as a five hour window or an eight hour window? We don't know yet. So -- and or every other day fasting, and or 5:2, like five days on and two days off, or there -- there's so many variations of this. I don't think we have any idea yet what's really beneficial. And there are some people actually believe that you should just fast for three, four or five days, couple times a year and that's all you need. So, is intermittent fasting, are you getting all the benefits? I don't know. I think there's good scientific studies suggest there's a lot of benefits even -- in the ones in humans particular. But is that the best way to do it? I don't know.


TODD: Forget about some of the more science based touted benefits we talked about. Is intermittent fasting worth a try for people trying to lose weight?

DR HORNER: I think it's definitely worth a try. I mean, I think there's enough evidence that it is beneficial. And it may be probably two -- for two reasons. One is, again, when you intermittent fast, I think you eat less. So, you're -- it's a form of caloric restriction and it's probably a healthier form than, you know, sort of constantly just always being restricted. And that -- so, that's one, right? And then the other reason is that the sort of toning effect that it has for you on how you deal with sugar, and you know, and how you’re -- how you regulate insulin, that's also probably beneficial for someone who wants to lose weight, right? It's likely that that would be beneficial for people's cravings and so forth, that effect over time. So, I think it's definitely -- I would say it's definitely worth a try. If you're wanting to lose weight, you know, I think this is a really good try. And I would -- something to try. Because it's not, it's not hard, right? It's not complicated. It usually fits in with most people's lifestyle. So, I would --I think it's definitely worth a try.

TODD: How do juice fasts and -- or liquid diets compare? Are they just completely different animals ‘cause you're still getting your nutrition that way?

DR. HORNER: Yeah, I think they're different in the sense that they're not a real fast, right? So, when you're on a juice diet, you're still taking in some calories, you're just not -- you've eliminated a lot of protein and so forth from your diet, so you're getting a lot of nutrients. So, it is different. You're still metabolizing stuff when you're on a juice diet. So, that's -- to me that's almost like a true caloric restriction diet, really more than an intermittent fast.


TODD: I can remember when people were touting the benefits of grazing, kind of eating small amounts throughout the day, which seems to be almost the opposite of intermittent fasting. Can both work?

DR. HORNER: You know, that’s a really good question. Again, I -- overall, so, you know, the answer to the question's always gonna be what are you grazing on, right? So, the quality of what you eat is probably really important. I'm a grazer, so that's what I do. I definitely eat more than three meals a day. And I think that's probably because again, I like to work out, so it kind of -- I'm -- it just fits what I like to do, you know. But again, if you're grazing and that's mostly snack foods, right, and it's maybe high caloric snack foods that aren't good for you, that's probably a great formula for gaining weight, right? So, grazing in high quality foods, like for example, if you eat an apple, right, an apple is like a super food, right? It's great for you. It has proteins in it that we know improve longevity, lifespan, and it's fiber so it makes you feel full. So that's a very different, like if you're grazing on apples and high quality foods like that, probably it's -- can be as good for you than other approaches such as intermittent fasting. And there are studies to show like if you, again, if you were to, you know, it's -- less important about when you eat and how often you eat, if you control certain aspects of your diet, you can also achieve an increase in fat burning, you know, this ketogenic state. You can do that by diet alone. There is -- there is evidence of that. Or in particular, diet and exercise.

ZACH:  Whether it's because you hope to lose weight or the other possible health benefits intrigue you, you've decided you want to try intermittent fasting. Here are some of the things the experts think you should know. Make sure your routine is healthy beforehand. If you have a poor diet going into intermittent fasting, it's not going to serve you well. Create a habit of protein and fiber pacing for a few weeks before you start fasting. Cut down on late night eating. Don't eat junk food after a fast. The biggest mistake most people make with intermittent fasting is thinking they can eat anything as long as they stick to the fasting window. Eat healthy, stay hydrated. Water is important, and most plans allow coffee or tea. Intermittent fasting is not for everyone. Those for whom it is likely not a good idea include anyone who has diabetes and is at risk of hypoglycemia, AKA, low blood sugar. People with a history of an eating disorder. Individuals on medications that require regular eating intervals, pregnant and breastfeeding women. Anyone in those groups should absolutely consult their doctor before starting the regimen. Adjusting to a new dietary pattern may cause some mild symptoms, but seek medical attention if any symptoms become severe, particularly changes in blood pressure, dizziness, fainting or nausea. Disruption of your sleep or menstrual cycle should also prompt you to stop intermittent fasting.


TODD: Based on what you've read on it, you like the taking a full 24 hour fast, maybe not every other day. But I think the -- what I read is the more popular form is maybe twice a week. You don't eat for 24 hour periods and then eat normal the rest of the time.


DR HORNER: Yeah. I think that if I were going to try to do a study on myself, I probably would go for more of that, which is, you know, either every other day or the 5:2, which is five days normal and two days fast. I just think that it fits my lifestyle a little more, but I think that that's probably what I would go for. ‘Cause I guess I like to eat too much.


 So, I think it'd be hard if every day I knew I only had a short time to eat, so.


TODD: All right. Anything else you wanna add about this?

DR HORNER: Oh, I did wanna mention another thing that there's some interesting science too around which we haven't touched on, intermittent fasting seems to change your gut biome. So, the bacteria that colonize your gut, it seems to have a big effect there. So generally, this is a very general statement, but in general, when different species of bacteria over colonize, become too much of the majority in your gut, it's usually associated with poorer health, typically inflammation. But it looks like intermittent fasting seems to increase -- and this is -- these are human studies that look pretty exciting. It increases the diversity right, of the bacteria in your gut. And that's probably a good thing for a lot of different disorders as well. There's a big correlation between gut health and a variety of conditions. And there was even a study, and this is in my field, which I think is kind of like science fiction, but it's a recent study which is really exciting. So, these are -- this is in rodents again, but they injured the nerves of these rodents, so the peripheral nerves of the rodents, and they showed that if they put the rodents on the intermittent fasting, that their nerves grew back faster. Even more interesting in this study, they showed that that growth was probably due to an improvement in their gut health. So, they could actually find a specific signal that came from bacteria in their gut that was beneficial to the regeneration they had. So, I wanted to bring that up ‘cause I do think we often focus, you know, if you have a neurologic condition or cardiovascular condition, we often focus on that particular organ, but we're systems, right? We're a system and all the organs really participate in our health. And I think that the beauty of that integration and how all the systems need to work together, I think that's really exciting stuff. This is, again, in some rodents, it hasn't been shown in humans, but I like the analogy really with how we should think about our bodies, right? If you have something wrong, if you have a skin disorder, you can't -- you gotta not just treat the skin, but you gotta treat the whole system, right? Everything works together. When any one part of our body goes offline, you know, it's not working. Like if you're overweight for example, that's not just one thing, it's the whole system needs to be kind of reoriented for repair.

TODD: Yeah, that's interesting. And in my reading up on the subject, I had never -- didn't come across anything about gut health. So, it's perhaps better than a probiotic? 


DR HORNER: It Could be. The probiotics, I think, whether they -- whether you can transform a gut biome, that's what we call dysbiotic, meaning that, you know, some bad species of bacteria has over colonized your gut. The evidence of just taking a probiotic to reverse that or benefit are pretty low, you know, in human studies. In fact, what you see now is it's more likely that you literally have to transfer the biome, sort of replace the biome and that's, you know, by e -- you know, if you've heard of like -- it's sort of adoptive transfer of biomes from one human to another. I mean they're doing this in clinical studies as well. So, where you literally take the gut biome of a healthy individual and you, first you delete, you know, the person that has this dysbiosis. So, you give 'em an antibiotic, you kill bacteria and then you recolonize the whole biome with someone else's biome, right? And that's why I think, you know, people are going to those extremes because I think just taking a probiotic probably can be good for health in general, right? But if you’re really dysbiotic, if you really have a pathological problem in your bowel, I don't think that that's sufficient to reverse it. It seems like you need something more significant. And intermittent fasting might be one of those things, right? Because through the fasting period you might be giving the good bacteria a chance to recolonize. And why would -- why is that? So, there's even studies suggesting that when you're -- when you have this dysbiosis, when the gut -- when your gut is kind of, there's some bad bacteria growing in your gut, they signal back to your brain to make you crave certain kinds of foods, right? ‘Cause they're eating, they're trying to direct your body what to eat and how much to eat. So, there is evidence of that. So, it could be the intermittent fasting maybe helps with that just by simply, you know, creating that fasting period, that period of repair, repairing the gut and allowing, you know, the normal sort of flora and fauna that's there to recolonize or re-effect it. Now I'm hypothesizing to be sure there, but there is studies that suggest that when you ha -- when you're dysbiotic, when you have these bad bacteria or single, you know, just one or two species of bacteria that overgrow, they can have a very strong effect, a negative effect on your overall health, but also things like cravings and so forth can be really bad.

TODD: All right, very good. Certainly, an interesting topic. You think it’s -- this phenomenon is here to stay?


DR HORNER: I think fasting is here to stay. And I wonder -- and will there -- I often wonder is there gonna be a fasting pill, you know, one that makes either fasting easier or mimic some of the effects. Maybe we can learn, you know, a pill that will help, you know, turn on some of these genes that fasting seems to turn on, so. But I think it's here to say, I think it's pretty robust.


TODD: No one's working on that pill yet, are they?


DR HORNER: Well, maybe somebody we don't know about.



TODD: All right. Very good. Well, I appreciate it. You're taking time to talk about this with us.


DR. HORNER: It was my pleasure.


ZACH: So, Todd, after hearing all that and your limited experience with intermittent fasting, would you potentially try a different approach? I know you tried the 16:8, didn't seem to be a big fan of it, but as we discussed, and as Dr. Horner discussed, there are lots of different ways to go about this. So, would you be interested in trying another one? I mean, I, for me, who hasn't tried it at all, I think I'll probably give one of these a try, but what about you?


TODD: I'm in no rush, but I want to see the results of -- see a little bit more evidence out there, but I definitely foresee at some point in my future doing a one or two day a week fast, eating five or six days and fasting one or two. We'll see how that goes. But I -- I'd like a little bit better evidence on this before I do.


ZACH: One of the things that makes me hesitant to jump into something like this is I feel like, man, if I don't eat anything today, like I'm -- I don't know if I can like focus. I feel like my brain would be kind of all over the place, but it was surprising to me that he kind of said the opposite.

TODD: Well, I think there is an acknowledgement that if -- when you start this or at the early periods, it can be difficult. You - people refer to how you become hangry.


ZACH: Big time hangry person right here.


TODD: Right. But at some point, you hit a zone and I know this from the juice fasts I've done, you hit this, this period where you do feel mentally clearer and you do feel better energy. That's what interests me about it. Generally, I'm like Dr. Horner. I like eating and I see it as fuel, especially like, when I do workouts on a daily basis. I wouldn't want to curtail that. But if you can do it just periodically, I like the idea of the benefits that it might bring.


ZACH: Yeah. Just to reiterate that, if you are someone who's exercising on a regular basis and you wanna do the day on, day off, don't take the day off the day you do your exercise, you're gonna need that energy and those calories to perform.


TODD: Right. That would be the way I would do it is I would do it on a non-workout day. But because when I work out, I mean, the first thing I do when I finish my workout is to take in protein and fuel that help my -- restore my muscles.


ZACH: If you are gonna try this, there is a period of time where you have to acclimate, right? You can't try it for like two weeks and then say, “Well, I didn't lose any weight.” Or, “I feel like my mind's as clouded as it ever was.” Right? You, gotta really, like any habit, you gotta give it a full try before you say it didn't work for you. And it might not work for you, but if you are gonna try it, see it through to a reasonable period of time before you call it quits. 


TODD: Yeah, absolutely. He said one month which seems reasonable to me. Especially if you're doing the 16:8, if you're doing more of a six day fast one day -- I'm sorry, six --


ZACH: Six-day fast, huh?


We do not recommend a six-day fast.

TODD: If you're doing a six day eat, a one day fast, you probably would want to do it for longer than that.

ZACH: Great. Well, I think it was a unique approach for us to talk to a neurologist about this, ‘cause the dietician side or all the nutritional side, that's well covered ground. And we try to look at things from, you know, new angles that we possibly haven't before. And I found it very insightful talking to Dr. Horner about this.


TODD: Yeah, He had a --he's up on the research and had a lot of things that he talked about that certainly are exciting researchers. I know, just the idea of anything that could prevent inflammatory conditions such as Alzheimer's or arthritis as I get older, sound very appealing to me.


ZACH: That's gonna do it for us this week on the On Health Podcast, and we encourage you all to go to our blog at and to share, like, and subscribe to our podcast. New episodes drop Tuesday mornings. So, until then, stay tuned and stay healthy.

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Categories: Tips to Live By