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Can you live longer by changing the way you eat? 

There are many claims out there about intermittent fasting and its impact on health and longevity. Some people say you can extend your lifespan just by rearranging the time window of when you eat every day. 

Is that true, though? What does science say about fasting in humans and its effects on how long you’ll live? 

Rather than examining this myself, I invited an intermittent fasting expert, Dr. Grant Tinsley, to explore the topic. Grant has been on the podcast before to discuss body fat measurement techniques, but as a scientist who’s been involved in many time-restricted feeding studies on athletes, he’s the perfect guest for this topic. 

Grant is an Associate Professor at Texas Tech University, the Director of the Energy Balance & Body Composition Laboratory, and is a Certified Strength and Conditioning Specialist (CSCS) and Certified Sports Nutritionist (CISSN). He has over 150 peer-reviewed journal articles and abstracts, with his major research interests being sports nutrition strategies, body composition assessment techniques, and intermittent fasting in active populations. 

Grant and I chat about . . .

  • The role of mTOR, AMPK, and sirtuins in aging
  • Metabolic age versus chronological age
  • Rodent metabolism and why we can’t apply research in animals to humans
  • Autophagy, how long it takes to ramp up with fasting, and whether it matters
  • Who should try fasting and who could potentially benefit
  • Fasting’s effects on muscle retention
  • And more . . .

So, if you’re interested in the science of fasting’s effects on longevity and how seriously you should take bold claims about lifespan and time-restricted feeding, check out this podcast and let me know your thoughts! 


0:00 – Try Whey+ risk-free today! Go to and use coupon code MUSCLE to save 20% or get double reward points!

5:45 – Is intermittent fasting essential for overall health and longevity?

10:11 – What are some of the things that people are looking at in research and are being extrapolated into humans? 

16:05 – What are your thoughts on the validity of metabolic aging?  

22:36 – What are the benefits of fasting? 

25:44 – What are some reasons I should consider fasting?

27:26 – What are your thoughts on fasting increasing longevity?

35:23 – How long do you have to fast for to make a meaningful health difference?

41:25 – Does fasting cause muscle loss?

49:03 – What are your thoughts on the importance of minimizing mTOR to maximize longevity? 

1:01:30 – Where can people find you?

Mentioned on the Show:

Try Whey+ risk-free today! Go to and use coupon code MUSCLE to save 20% or get double reward points!

Grant’s Instagram:

Grant’s Website:

What did you think of this episode? Have anything else to share? Let me know in the comments below!


Mike: Hey ho, and welcome to another episode of Muscle for Life. Thank you for joining me today. I am your slightly congested host, Mike Matthews, hence the nasally voice. But fortunately, I was not congested when I conducted this interview, so you won’t have to listen to this for long. And in this interview, you are going to be learning about fasting and health and l.

A very popular topic these days, mostly because of some credentialed and well-known experts who have been beating this drum loudly for a couple of years. Now, according to some of these people, you can live significantly longer by just rearranging. Your meal times by extending the amount of time every day that you don’t eat and compressing the amount of time that you do eat into a certain window.

Maybe it’s four hours, maybe it’s six hours, maybe it’s eight hours. It depends on the person and the protocol, but the premise is always the same, and that is that many very good physiological. 

Happen when we are fasting, when we are not eating food, and when our body is not processing food. And so insulin levels are at a low baseline level, and so the more that we fast, the more these good things occur, and the more these good things occur, the better our health and our longevity.

How true is that hypothesis though? It is compelling. It sells a lot of advertising space on podcasts, and it sells a lot of books, and it sells a lot of speaking engagements. But is it supported by the weight of the scientific evidence? What good evidence exists for that hypothesis? What good evidence exists that casts doubt on that hypothesis?

Well, those are some of the questions that you are going to be getting answers to in today’s episode. And you are not going to be learning from me today, but instead, you are going to be learning from an intermittent fasting expert and researcher, a published researcher, a true scientist, Dr. Grant Tinsley Grant has been on my podcast before to discuss body fat measurement techniques, but as he has been involved in many time restricted feeding studies and especially on athletes, I thought he would be the perfect guest to come back and talk about intermittent fasting and health and longevity.

And in case you are not familiar with Grant, he is an associate professor at Texas Tech University. He is the director of the Energy Balance and Body Composition Laboratory there, and he’s also a certified strength and Condit. Specialist as well as a certified sports nutritionist. Grant has over 150 peer reviewed journal articles and abstracts to his name with his major research interests being sports nutrition strategies, body composition assessment techniques, and intermittent fasting in active populations.

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Hey Grant, it’s good to see and speak with you again, not over email . 

Grant: Absolutely. Yeah. Thanks for having me. 

Mike: Yeah. Yeah. I’m excited for today’s conversation, which is something I’ve been getting asked more and more about recently, and that is intermittent fasting, which has been popular for some time now.

Again, based on the questions I’ve been getting asked that the conversation has changed a little bit from body composition. You remember years ago, a lot of people were speculating that maybe if, or some sort of fasting diet is better for body composition than traditional eating, and then the weight of the evidence now shows that’s not the case.

It can work just fine if you like it, and there’s no reason to not do it if you like it, but you are not going to automagically get bigger, leaner, and stronger simply because you change up your meal scheduling. Okay, fine. So that was the discussion for a bit, and now it seems like the discussion is more centered around health and longevity and there are.

People out there, in some cases, very credentialed people, smart people who are making some pretty strong claims about intermittent fasting and health and longevity in some cases. I mean, they’re basically saying that following some sort of fasting diet is significantly better for your overall health and longevity than just traditional eating.

And so if you want to live the longest and healthiest life that is available to you, given your genetics and your fate, you want to be fasting in some way. And there are different ways of doing that. That’s, again, that’s the type of stuff that people are asking me about these days. And so I wanted to get you on the show because you’ve done research on intermittent fasting and maybe more in the body com space.

But this is an area that you are definitely qualified to speak in. You know more about this than I do. So here we are and I’m gonna stop with that. And uh, as the Twitter blue checks like to say, I’m gonna shut up and listen now.

Grant: No. Yeah, I mean this is a really interesting topic, a big topic, a challenging topic, you know, like the body comp, uh, you know, claims both at the individual level and the research.

That’s something that is fairly straightforward to assess. You know, last time I was on, we were talking about the error in body composition devices. So we know, you know, body composition assessments aren’t perfect, but it is something we can estimate with reason. Precision. Uh, if we’re talking about longevity and especially applying these programs to humans, we get into a little bit of a conundrum with, you know, how we assess this.

I’ll say, I guess as an introductory comment, a big thing I’ve noticed is that, uh, individuals, and as you mentioned, sometimes very credentialed individuals, very persuasive individuals with a good, you know, research record and. I think it’s common to group any form of fasting as one thing. It’s like, oh, you do fasting, here are all these physiological effects that you can expect that would delay aging, promote longevity, and so on.

Um, but to start with, they’re not even really defining the fasting programs, you know, how extensive these are. I mean, as you know, and many listeners will know, there’s certainly a huge spectrum of intensity of fasting program. In terms of the duration of fast, whether or not it’s a, a real fast or a so-called modified fast, the frequency of the fast and so on.

So I think often benefits that are largely coming from non-human species are not only applied to humans directly, but sort of applied to any fasting program anyone is doing. So, you know, someone could be listening at home and be like, oh yeah, you know, I’m doing, I’m eating all. Calories in 12 hours a day, and I’m fasting 12 hours a day.

So I can expect these really substantial longevity benefits when if you kind of trace back the origin, the evidence on that point, that that may not really be correct, or it may just be, uh, some large jumps away from kind of where, where we started. 

Mike: Yeah, I mean, skipping breakfast is kind of what a lot of people do, right?

And it should just be a red flag for, for listeners if you hear that doing something relatively simple like that, skipping breakfast is supposedly going to revolutionize your, your health or is going to significantly extend your longevity, not give you one or two more days, but give you several more years and improve the quality of the time that you have.

It’s not a hard and fast rule that simple changes like, you know, if we go from getting enough sleep to getting enough sleep, that’s a pretty simple change that actually will make a big difference, but, I, I think you would agree that generally speaking, it’s a red flag when somebody says you can just do some little thing that, that really requires no effort and get major benefits from it.


Grant: Yeah, no, absolutely. 

Mike: Now, in the case of longevity and, and some of the research that is used to support some of these claims, like what are some of the molecules, what are some of the things that people are looking at in research and then extrapolating, and it can be from animals or it could be in vitro, or it could be in vivo, but it’s just kind of an interesting mechanistic thing that, again, is being extrapolated into humans or into healthy humans or just saying, Hey, because of this mechanism, these great things are going to happen.

It hasn’t been proven yet, but that’s my prediction, you know? 

Grant: Yeah. So that’s a great question and I’ll, I’ll try to be fair, uh, to both sides and not let my personal opinions come across too strongly, at least in this initial discussion. So I’ll start by saying that, My understanding of the rationale for applying.

Some of these studies and model organisms to humans is the fact that some of these longevity related genes are conserved across species where we might see a similar pathway in yeast and mice in humans. So, you know, that makes sense. We can draw some, some inferences like jumping up the species, say jumping from mice to humans.

Clearly there are some important caveats and we, I’m guessing we may get into that at some point in this conversation, but I’ll start there and saying there’s a rationale. I don’t think these people making these claims are, are just, you know, making things up. They’re, they’re starting from somewhere. So some of the major longevity related genes and then subsequently, you know, the proteins that will be produced from those genes.

That I’ve seen identified, interestingly enough, maybe familiar to some of the listeners who, uh, you know, are really interested in exercise or have an exercise, uh, science background because a couple of them are some of the usual suspects we think of in, in terms of adaptations to exercise. So the mTOR pathway, for example, mammalian or mechanistic target of rapamycin.

This is a really interesting one and a bit, I guess, controversial. It’s, it’s funny cuz from the exercise side, from the nutrition side, uh, from the gains side, the gem side, I feel like there’s a decent familiarity with mTOR. Just knowing mTOR is a major anabolic pathway, important for protein synthesis and muscle and else.

So I think there’s a lot of messaging about mTOR from, again, from the exercise and Nutri sports nutrition side that’s gotten out there saying like, you wanna maximize mTOR all the time. Amino acids, you know, stimulate mTOR, especially the branch chain amino acids, especially leucine. Uh, and that’s one point where we’ve gone down rabbit holes and, you know, the sports supplement industry at different times about, you know, really focusing on one particular amino acid.

But in the aging realm, the focus is the exact opposite. Not increasing mTOR, but suppressing mTOR. According to some people al almost at all 

Mike: costs. Yep. Protein restriction comes into this, um, calorie restriction, like intentionally kind of making calorie restriction a lifestyle like a calorie deficit.

It’s no longer a weight loss intervention. It’s a lifestyle.

Grant: Yeah, no, absolutely. So, and I’m happy to return to mTOR Bell. I’ll, I’ll go through my list. Cause I was already off on a tangent there. So, mTOR being one, um, you know, pathway instead of genes that would be linked to longevity. Another is AM M P K.

So, uh, those of the listeners who have had maybe some exercise physiology, maybe familiar with this as a cellular energy sensor, that’s important for say, some of the mitochondrial adaptations you would see with multiple types of exercise, but sometimes viewed more on the kind of endurance aerobic exercise side.

And then some of the really popular ones, partially because they are the research area of one of the really, um, p. Figures or communicators in this area are the sirtuins, which have a variety of effects related to the mitochondria, also to DNA packaging. There are a number of sirtuins, so it’s not necessarily like one function, but those are a few, um, items that have been identified now sort of related to that.

And we can come back to those. But there are also, in terms of longevity, there are ways we’ve tried to, we as scientists generally have tried to quantify this. Um, you know, there is a recognition, and I think everyone in the fitness realm will be on board with this, saying that our chronological age is not the most informative.

We certainly see people who are older, who have, you know, followed a healthy lifestyle for a long time, who have, you know, by, by all relevant metrics, are healthier and potentially have more years of life ahead of them than someone who’s younger and has not, you know, done the lifestyle. Things that would essentially promote good health and longevity.

So there are a few ways that’s been looked at. One that’s really, it seems like maybe is winning out is kind of our molecular age or how we would look at longevity, um, or maybe even track longevity, uh, is related to, uh, dna. N a methylation, d n a methylation would be an example of what’s called an epigenetic change.

So a change to your dna n that doesn’t involve an actual change in the sequence of, um, what are called nucleotide bases. So kind of the individual units of dna. N we’re not changing the sequence of DNA N but we’re kind of attaching or detaching certain molecules, uh, in this case methyl groups, which are just a carbon with three hydrogens on them.

Um, attaching them at certain points in the dna. The methylation at very specific parts of the DNA has been fairly well correlated with chronological age. And kind of the next step they’re looking at is, can we kind of track this or can we modulate the DNA methylation and interpret that as. A change in someone’s biological age, like, can we reverse aging?

And there are definitely a few leaps involved there, from my perspective, from what has been shown for sure with some of these, these clocks, um, epigenetic clocks or DNA methylation clocks, uh, to where people, anti-aging people, longevity people really want to go with it, which is, yeah. You know, do this intervention, do fasting, whatever it is, and let’s track your epigenetic clock and, uh, let’s try to show that you’re aging backwards or, you know, uh, just promoting longevity. So yeah. 

Mike: Yeah. Quite a few, um, threads that we can pull on there, but I just wanna first follow up with what you were just talking about, metabolic age. Sometimes people will ask me about that. And so what are your thoughts on the validity of that? You, you, you explained a little bit of kind of inner workings of how they’re, how they’re coming up with this assessment, it sounds like.

You are skeptical, uh, or, or maybe you find it interesting but are not sold on the sales pitch just yet. People when they’re paying for whatever, whatever it is that they’re doing, or when they’re trying to, to, to do things to improve their, their biological age or improve their metabolic age, ultimately there are very specific results that they’re after, not just seeing a number going down, like they are taking that to mean that they are healthier and will live longer.

And so anything that gets that number to go down, they associate with better health, better longevity.

Grant: Yeah. I answer in two parts. One, and I won’t pretend have full knowledge of every, you know, age related test that’s out there. I know there there’re a number, so I’ll speak to the ones I’m familiar with, which seem to be fairly popular and not necessarily naming names, but some of the aging related metrics I’ve seen that are available to consumers.

Or you can pay for this. You know, you send in a blood sample, they tell you your metabolic age or biological. Some of the ones I’ve seen essentially to me seem like they’re taking fairly standard health markers. So like things you would get from a normal blood panel, normal body measurements, anthropometrics, and so on in sort of putting it into an equation or a method that will distill this down to an age for you such that if you, you know, were to implement some lifestyle changes, say you reduce your calorie intake, you lose some fat, you see some improvement in these normal health markers, uh, and you send in another blood sample, you might see your biological age go down, which might be interesting, but it’s really just related to kind of normal health markers.

You’d always already be aware that they’re relevant to health in kind of the major diseases that would come into play as you age. So just as a concrete example, you know, you send in your first blood sample, you get age back and they say you’re 50 years old on the. You implement some of these changes, your, you know, LDL goes down, um, inflammatory markers go down, you lose some weight, this and that, you send it back in.

They’re like, oh, now you’re, you know, uh, what, what age did I say, sorry, did I say 50? Okay, now you’re 47 . So, you know, maybe that’s helpful for some people, but if it’s using fairly standard markers, there’s nothing too or shattering there now. So that’s kind the first part. That’s what I’ve seen currently on the market.

Mike: So that’s kind, that’s kind of just marketing then it’s just a different way to market standard. Testing protocols? 

Grant: I think so. And to be fair, I haven’t seen like the proprietary algorithms being used, so maybe they have, you know, really valid ways they’re waiting each of these things where they’re looking at it and they’re like, for this inflammatory marker, we’ve seen this relationship with mortality, this relationship with aging markers, you know, so on where, where they have things weighted well, so like may, maybe it is valid or more valid than just the consumer interpret, trying to interpret all these different health metrics.

Um, cause I’ve seen some that are using about like 20 or so input variables. So maybe marketing or, or maybe yeah. You know, just like helping the consumer make sense of things. So I’ll, I’ll try to give a generous interpretation there. 

Mike: I mean, the simplification of course is helpful. I mean, for people to get a scorecard of sorts, there is a psychological appeal to that.

So that doesn’t necessarily have to be misleading or inappropriate.

Grant: Yes. Now talking about the more advanced clocks, like I was talking about with the, uh, D n A methylation, so kind of epigenetic clocks. To my knowledge, I’m guessing you could probably pay for them somewhere. To my knowledge, these are not yet widely available, but hearing again, some of the communicators in this area and researchers in this area speak about this, it is certainly much more accessible than it was, you know, a decade ago, two decades ago and so on.

Just with advances in, in D n A sequencing, it seems like it’s moving towards a point where you could have this assessed relatively frequently and relatively inexpensively. So that will be interesting where you’re assessing something that is not, at this point, a standard clinical marker. I’m not sure if that will get to the point where it is a clinical marker where, you know, if you’re getting your blood panel done, they’re also testing the DNA n a methylation of these certain locations.

But kind of as a bigger picture perspective, and I’m gonna use a, a body composition example here on the DNA methylation, and I won’t pretend that this is my exact area of research interest, but it touches it on this kind of fasting realm. It, it seems to be fairly accurate at estimating your chronological age.

So not, not knowing someone’s age or say knowing someone’s age, but just looking at the data from their DNA methylation. Um, I’ve seen some estimates where it’s like, on average it can get within, you know, like three years of your, your actual chronic logical age. So it’s like, oh, you know, that’s interesting.

That’s good. So the body composition kind of parallel here is, you know, at a point in time you can come in and get on a at-home body fat scale and it say it gets you within 3% plus or minus 3% of your actual body fat percentage. You’re like, okay, that’s interesting. Most devices can say, they can distinguish between someone with like much higher body fat, like intermediate body fat, lower body fat.

So like, it’s okay at this one point in time it seems like people are taking that step further and saying like, okay, here’s your, your DNA methylation, here’s your, you know, metabolic age biological. Do something. We expect that this can track a change in your metabolic age. Same thing as body composition.

We expect that this at home body fat scale can track a change in your body fat percentage. So then it’s kinda like on the body comp side, you come back, you’re like, okay, my body fat percentage went up by 1%. Like, is that, is that a real change for your device for many devices if be No, that’s well within the air of the device.

Similarly with the DNA methylation, I haven’t seen, and again, not my exact error, but I haven’t seen convincing data that’s would relate this to say, um, we can definitely track your age or like a change in these variables would translate to in improved longevity. With the major caveat that you can’t truly do that research in humans right now, at least experimentally it would take, you know, many years it’d have to be observational, be very hairy research.

It could, you know, it could potentially be done. But right now I would say the, there’s enough to go on that if someone’s really interested in this, they might want to, once it’s available, test their metabolic age, biological age and pay attention to this. But I wouldn’t put. Too much stock in it yet. 

Mike: Now in the case of fasting, and let’s just take standard clinical markers, some of the things that you mentioned that are well researched and we know if this one goes up, that’s bad.

If this one goes down that’s good, or here’s the range of good and bad and so forth. What are your thoughts on claims that fasting alone can create significant benefits that or, or that can benefit you in significant ways that can be verified just in standard clinical markers? 

Grant: Yeah, I would say the majority of the evidence that I’m aware of, which again, this, this is closer to my research error, would not.

Show a substantial improvement in normal clinical markers with fasting in the absence of say, calorie restriction and weight loss, there are some exceptions typically with fairly specific forms of fasting. So like early time restricted eating where you might have individuals eating breakfast, you know, eating lunch, ultimately cutting off their calories for the day.

In the early afternoon, say like 2:00 PM maybe 3:00 PM there have been some short-term studies of early time-restricted eating that have shown health benefits, say, related to, um, glucose metabolism, for example, uh, independent of changes in weight loss. So there are some, you know, relatively small, relatively short-term, relatively specific studies that have shown unique health benefits of fasting itself, not just calorie restriction, not weight loss.

But if you were to view this from the big pictures perspective, how many individuals practice fasting and look at kind of the totality of the evidence. I’d say there’s not very strong support for that with some caveats again, that if, if someone was following, um, a particular eating pattern that was very out of sync with what we would view as ideal.

So I guess if, if we wanna get into this, if they say, just for the sake of example, every someone is eating the vast majority of their calories late at night, for example, there are some decent documented effects that are, that are relatively negative late at night. So if you were to consume the exact same meal in the morning and late at night, your metabolic responses will differ.

There’s, there’s fairly strong, um, research on this. So if you took someone again that was, say, consuming a lot of their calories late at night, put them on maybe a normal intermittent fasting, say time restricted eating type program, it might be a setup where you would see a change at the individual level.

Uh, I hope that’s coming across what I’m, what I’m trying to communicate there. Yeah, 

Mike: yeah, yeah. No, I, I’m, I’m following. Can you speak to the context of, let’s say you have a healthy individual, healthy body composition, exercising regularly, eating a lot of nutritious foods, getting enough sleep, et cetera, et cetera.

How likely is that person to benefit from switching from, let’s just say, a normal diet, not loading all their calories at night? Just, uh, I’m gonna take myself as an example. I just like to eat something every few hours. I do like to eat a bit more food. I’ll have a bigger dinner than a, than a lunch or a breakfast.

Just cause if I eat too much food, I feel like. It slows me down a little bit mentally, like you get into the digest mode and a lot of my work requires thinking and listening and writing, and so I, I like to kind of eat light throughout the day, at least into the afternoon. And then I can go brain dead for the rest of the day and it doesn’t matter.

So I do skew my calories a little bit toward later in the day. So, so I’m eating more traditional eating pattern. I’m relatively lean, I, you know, I do cardio five to seven days a week, lift weights, blah, blah, blah. Is there any reason why, if we look at it again from the perspective of health and longevity, why I should consider fasting?

Grant: I would say at this point there is not a compelling reason to do so. I think the. Potential for benefits given everything you described, given the activity status, activity level being a huge thing, given the assumption, which I’m sure is correct of you following a relatively nutrient dense diet, a nutritious diet and recommendations with lots of, you know, recommendations for health, athletic performance, and so on.

I would say the potential for benefits is relatively small. Now, if you told me that you’re like my number one concern, Longevity and health, and I’m okay, like trying something on unfairly limited evidence. Like I’m, I’m willing to fast. That’s no problem. Any, something like that. And you’re very optimistic about it.

I’d say, you know, you, you could incorporate fasting even if it wasn’t daily. And we can get into this on the duration of fast that have shown kind of impressive benefits in all organisms and how that might translate to a human. But I’d say if, if you’re all about it and you wanted to do like a one to two day, um, fast, even monthly, something like that, then go for it.

But I would not say like, yeah, you definitely need to do that, or if you do that, you’ll for sure live two years longer. I just don’t think we’re at the point where we can make strong claims. So again, I would say to summarize, it’s in the realm where if someone’s really interested in it or they want to, or they’re like, I’m willing to take a risk on this.

I just, I don’t wanna, I don’t wanna die , I don’t really take a risk on this. Um, then, then sure, you know, like, go for it. But it shouldn’t be presented as, yeah, you really need to do this or else you’re just gonna live to average life expectancy. And you could have had, you know, like another decade with your loved ones or anything like that.

Then we 

Mike: play the, the Steelman game and then say, all right, well, given your understanding of everything you’re explaining, maybe what is a, a best case scenario that you could see happening. Not like a 0.11% probability, but if things panned out the way that some people are saying that they will, what might that look like?

And you mentioned a one or two day fast every so often. Like what could somebody do if they wanted to try to get ahead of the research, so to speak? Or they, they are very concerned about living as long as they can. Or maybe, you know, I know some people who are older who are now more aware of their mortality.

It’s not something they ever thought about. And the idea of getting maybe a couple of more years of good years, Is very, very appealing. And if that means that they just eat less food or starve themselves, uh, one or two days a month, if that alone could do it, then they’ll do it. So maybe you can speak a little bit to that.

Grant: Ooh, yeah. Okay. So I’m, I’m happy to, I’m gonna give one quick caveat just about the elderly individuals and, you know, they’re clearly, clearly some trade-offs cuz we have known concerns about, say, muscle atrophy, sarcopenia, loss of functional ability in elderly, decreased appetite. There are many situations where elderly individuals may not be consuming enough protein, even the per dose protein, you know, where like say someone, say we have a good old Jim bro who’s been getting his 20 to 30 grams of protein, uh, at each meal all the way along as this individual ages, when they old enough, they’ll have a reduced anabolic response to that same protein dose.

So there are some considerations that would make you certainly wary of saying, oh, reduce energy intake, reduce, you know, protein intake and so on. So I’ll give that as a caveat. I’ll 

Mike: just mention for older listeners if you’ve found that your body doesn’t seem to respond to resistance training like it used to sometimes.

I’ve heard from people who, it turns out they were not eating enough protein, so their protein intake was generally just kind of low because they weren’t really paying too much attention to it. And to your point, they were generally eating smaller amounts, just, uh, you know, several times a day and that worked well when they were 20 years old, but it doesn’t work so well now that they’re 60.


Grant: To me, I think that is a notable. Kind of blind spot is the right word, but it’s certainly not emphasized by individuals who are discussing fasting for longevity. That’s often re recommended kind of what you’re asking, saying like, even at old ages you can start doing this and then you can potentially live longer.

But I think the, of course, quality of life and some of those muscle implications need to be, you know, particularly on the radar for individuals as. 

Mike: Because we know that that reduces having above average amounts of muscle above average amounts of amounts of strength, we know that that reduces your chances of dying from anything and everything, 

Grant: right?

Yeah, absolutely. And that’s a great point. I’m glad you brought that up, cuz to me that’s a lot more, that’s a lot more concrete. You can, you can take that to the bank resistance exercise good at any age, the muscle strengthening, maintaining lean mass, uh, you know, there’s even, you know, documented cases of very elderly individuals increasing lean mass, not only just staving off the decline.

So that’s something I’d say you can take to the bank and again, function so important. So I would take that to the bank more so than like, okay, here’s a, you know, pathway that I think we can feel late in our cells and this will cause me to live longer. But that’s causing you to like, you know, have impaired, essentially adaptations to exercise or something of that nature.

With all that said, uh, if I had to guess, I’m gonna start, start at mice for example. There are a number of studies, and this is true not just at fasting, but of other interventions. There are a number of studies with fairly impressive results in rodent models. Fasting is certainly one of this in calorie restriction.

Prior to fasting, me as popular, you know, there’s a lot of calorie restriction work in mice and other models. Something that’s come out that there’s increased awareness of in the last several years is that often the models of calorie restriction would be something that would essentially be like time-restricted eating for the mice.

So sort of for simplicity, the mice would’ve access to food one time a day when they’re trying to impose calorie restriction. So it was imposing calorie restriction that all worked. But as there was an increasing, as there has been increasing awareness of the metabolic effects of fasting, particularly relevant to rodent metabolism, which we’ll talk about in just a second, uh, researchers started to realize that they couldn’t necessarily disentangle all the effects of fasting in this long line of calorie restriction research.

So fasting proponents and even just critical observers would say, Some of these kind of profound benefits in here. Let’s make it more concrete. Life extension benefits. So like if you reduce the calories of a number of different species, they’ll live longer, say pre-human species for now. You know, some critical observables observers will look at that and say like, well, they were both fasting and reducing calories.

So what’s really going on here? There have been some recent studies that do support unique effects of fasting. That fasting really in some ways is driving some of those benefits in rodents. Now the big caveat here is related to, for me, is related to the duration of fast. So it depends, you know, some on the particular, say like mouse strain, but in general, say the metabolism mice would be approximately seven times faster than humans.

Humans would live approximately 40 times longer than mice. So there’s some issues translating, you know, a 12 hour fast, 16 hour fast, 18 hour fast from rodents, uh, into humans. Uh, thi this is probably an oversimplification, but just to like put some numbers to this. Relative to the, the resting metabolic rate being so much higher in rodents, a sort of 12 hour overnight fast for them might be more similar to a three to four day fast for humans.

And to take that further as rodents go beyond 10 hours of fasting, say between 10 and 24 hours of fasting, they’re losing easily over 10% of their body weight up to like 10 to 20% of their body weight in that amount of time. So that goes to show you that this is not comparable. If you see a rodent study where it’s like, wow, they, you know, they did 12 hour time restricted feeding, they fasted for 12 hours out of every 24 hours.

That is not the same as you or I doing, uh, 12 hour time restricted feeding. So I’ll say, if we’re gonna make a big jump from the rodent research to human research, we’d have to at least take that into. And say that some of these benefits we’ve seen with say, 12 to 24 hour fast in rodents. So that’s kind of where I’m getting at.

Like, you know, maybe it’d be more like a couple of days if you’re wanting to actually, you know, stimulate these pathways in a meaningful way. With that said, the shortest duration of fasting that I’ve seen any evidence for in kind of uniquely improving health benefits in humans, this is specifically related to autophagy, you know, which that, that term gets, um, used a lot in, in relation to fasting.

Autophagy just means self eating. It’s housekeeping process in the cells where, you know, misfolded or damaged proteins and other molecules are essentially broken down. So this is very important and skeletal muscle and elsewhere are very important for tissue health or healthy aging and so on. But the shortest duration of fast I’ve seen that promoted some benefit in some components of autophy in humans was 13 hours and they’re looking at from eight to 13 hours an increase in one component of this process.

There’s another study that after an 18 hour fast, they saw an upregulation of some of these. Genes involved in, uh, the autophagy process. So I wouldn’t say that’s enough to like take to the bank to say like, oh, I can just do a 13 hour fast or maybe even just an 18 hour fast and really capitalize on some of these potentially u unique benefits of fasting.

But just to be fair to both sides, I’ll mention those potentially interesting studies. Hey there, if 

Mike: you are hearing this, you are still listening, which is awesome. Thank you. And if you are enjoying this podcast, or if you just like my podcast in general and you are getting at least something out of it, would you mind sharing it with a friend or a loved one or a not so loved one even who might want to learn something new?

Word of mouth helps really bigly in growing the show. So if you think of someone who might like this episode or another one, please do tell them about it. And if that were to, let’s just say that the benefits related to I to autophagy and some of these other things actually did pan out. How often would you have to do, let’s call it the 18 to 24 hour fast to.

Make a meaningful difference over the course of, let’s say decades. So it’s something you’re gonna stick to for a long time. Best case scenario, and the reason why I’m asking that question is just because if you were to say it’s very hard to put. Actual numbers to any of this, but I wouldn’t be surprised if some of these things panned out.

If you could do this for a few decades and live for maybe another year or two, that’s good for people to know. That’s good . You know what I mean? Now, if you were to say it could be an extra decade, would also be good for for, because most people, they don’t want to follow even an intermittent fasting diet.

In my experience. Now, of course, the people who, like if they are consistently doing it, some of them like it, but most people who just want to lose fat, build muscle, get healthy. In my experience, working with thousands and thousands of, of them over the years, most people don’t. Like fasting diets. They don’t even like skipping breakfast because they like eating breakfast or they get too hungry.

Some people do enjoy a lot and, and the people who do in my experience generally just like to skip breakfast cause they’re like, eh, I’m not hungry in the morning anyway. I don’t really like breakfast food. It makes it easier for me to control my calories. Great. That works for me. But I, I think that most people listening, if they were to start incorporating 18 to 24 hour fasts into their lifestyle, They would not particularly enjoy it.

They would have to have a good reason to do it, you know? 

Grant: Yeah. I would say I would definitely personally err on the conservative side where I’d say, yeah, this is closer to the, and, and I don’t wanna put number to it, but I will, just for the sake of answering the question, , uh, of the two options you gave, I’d say yeah, this is closer to the, the year component.

You would be very 

Mike: surprised if at some point in your life it is there. There is a, a solid body of evidence that shows yes, you can live an extra decade if you just do these fasts 

Grant: every month. If that was the only change, like say in the absence of a difference in weight and like other clinical markers and so on, if it was truly just down to, you know, we’re messing with these epigenetic clocks, we’re messing with these signaling pathways, you would never know you’re healthier, but you’re gonna live a decade longer.

Yeah, I’d be very, I don’t think we need to focus solely on the longevity aspect. So we know, for example, going back to the clinical health markers, if someone has say borderline high blood glucose, um, if someone has a blood lipid profile that is not optimal and so on if for them, for that particular person because it’s easier for them cuz it introduces an energy deficit and so on.

If a fasting program led to improvements in those markers, I’d be more optimistic about that. Increasing their longevity and their just health span, how long they’ll be healthy and functioning well. And so, So, you know, those are, those are much more established clinical markers and that’s not unique to fasting per se, unless it is for the individual.

Unless they’re, like, if, if I eat, you know, throughout the day at a normal meal frequency, my weight always tends to drift up. You know, my, my clinical markers maybe in the wrong direction. I’ve heard some people, and I’m not saying some majority of people, but some people they’re like, fasting’s, the only thing that works for me, just cuz it’s, you know, it’s so simple, I can’t overeat really if I’m eating in the six hour window and you know, you could, but I don’t tend to overeat if I do this in a six hour window, uh, and then you see health improvements on that, then I’d be like, yeah, fasting is probably promoting your longevity because it’s in improving your health overall.

But yeah, in a vacuum where it’s like everything else is the same, just incorporating the fast and so on, I would err on the less optimistic side right now. I, I see many 

Mike: people making the mistake. I guess you could say that they’re kind of like stepping over dollars to pick up dimes where they’re not doing some of these foundational things like exercising regularly, ideally doing a combination of resistance and cardiovascular exercise, maintaining a healthy body composition, eating a lot of nutritious food, getting enough sleep, managing stress, and so on, and.

In lieu of that, they’re hoping that the power of fasting will override an 

Grant: unhealthy lifestyle. No, that’s a great point. So yeah, I would say your big rocks first, everything you just mentioned, exercise, sleep, nutrient, dense foods, calorie control, all those things. And if someone already has all that in place, and again, they, they have a high tolerance for like, you know, I’m, I’m down to do whatever.

I want to take my longevity to the next level. I want, you know, if there’s a 1% chance I wanna do it, then, then sure. If you wanna play around with that, my guess is that it would have to be pushing into to longer, fast. 18 hours daily. Maybe like in the future if something came out, it’s like, yeah, these, these benefits and rode really did translate to humans.

My guess would be, it’d be with longer, less frequent protocols where you had like a complete fast of 36 plus hours and maybe not as frequently, but I just think the duration, you know, people doing 16 hours, fasting, eight hours feeding each day, I think you’re really stopping short of the duration where some of these things might potentially come into play given, you know, human metabolism as compared to rodents and other species.

Mike: And when you say fast, you mean no calories, right, because that also, it depends who you ask. Some people say no calories, some people say, oh, well you can have some fruit and vegetables and you’re still fasting. 


Grant: it’s an interesting area. So there’s some data like on the like official fasting mimicking diet, you know, Five days or so.

Low protein, very low calorie, kind of specific foods and so on. You know, there are some some data supportive of health benefits of a program like that. But yeah, for the purposes of what we’re talking about, many of the pathways that you would be targeting relevant to longevity would be. From a longevity perspective, negatively impacted by potentially any nutrients.

So yeah, I would say complete fasting in this case. And this kind of gets back to like is it calorie restriction where I could just, you know, severely restrict calories down to 500 calories a day, uh, for a couple days. Would that be about as good as a 40 hour fast? We don’t have strong data on it, but if, again, if we’re making the full jump from like rodent to people, I would say the complete fasting really would be what you would need.

Mike: And what are your thoughts on potential implications, uh, in body composition? I know some people listening, they might a person who’s like, yeah, if there’s 1% chance I’ll do it. So I know some people they like the mental challenge of fasting. Some people it’s almost like a pseudo religious kind of practice, which fasting’s been a part of religion for a long time, so I understand that.

But I know that some of those people might also be worried about losing significant amounts of muscle. 

Grant: Yeah. So my general perspectives on this would. Certainly take into consideration training status, the goals of the person who they are. You know, believe it or not, I’ve had N F L dieticians talk to me about like fasting firms talking about like N F L athletes, individuals who are making, you know, their living off of performing athletically.

In those situations in particular, I’m usually fairly discouraging of any fasting. Um, unless it’s like at best it’d be like off season. Weight management is a big concern and very conservative, you know, in a bunch of other, uh, caveats. So if you’re talking about your, say, average fitness oriented, Individual.

You know, it still depends on training status. I’ll, I’ll say, well, okay, lemme start with this. I’ll, I’ll state what we have seen. So we did, probably the most relevant study we’ve done was an eight week trial and resistance trained females. And I think they had on average about five years of prior experience.

There were three groups, but you know, for the purpose of the discussion, I’ll talk about two. We had a kind of normal diet group where we’re required individuals eat breakfast and then they could eat at their desired frequency throughout the day. It ended up being about a 13 to 13 and a half hour eating window each day.

So, you know, fairly normal in one of the time restricted eating groups. Individuals had to skip breakfast. They first ate right around noon and they had about an eight hour eating window. Ended up being about seven and a half hours. Both groups consumed. As far as we can tell with the methods we have, uh, equivalent calories, they both consumed about 1.6 grams per kilogram per day of protein.

We supervised resistance training program for eight weeks. At the end of those weeks, we saw equivalent increases in fat-free mass as well as, uh, muscle thickness, like with ultrasound, directly looking the skeletal muscle. So we really did not see any impairment of the, the lean mass accretion that we had expect with progressive resistance training.

So I can say that in, in moderately trained individuals down to a seven and a half hour eating window with adequate protein, and there were about four, on average, about four separate feedings period of time, including whey protein supplementation. Immediately post exercise. Exercise was also performed in the Fed State, not the facet state.

So with all those caveats in mind, I would say down to that level, I would be comfort. For most people. Again, if you are either making a living for your physique or prioritizing that above all else, you’re gonna step on stage and so on. You’re a physique competitor, your severe energy deficit, you’re trying to hold onto all the muscle you can, something like that.

I wouldn’t necessarily recommend fasting, but with all those caveats I’ve already given down to that duration, I’d probably be okay. As you get shorten that, we really don’t know, but you know, at some point this will drop off. If you truly had someone doing omad one meal a day, even if they were getting 1.6 grams per kilogram protein per day, all in one meal, I would not be optimistic that they would long term have the same body composition as someone who is spreading those calories throughout the day.

And then what 

Mike: about the longer? So what about somebody who’s like, no, no, I want to do the 24 hour, I wanna do the 36 hour. Because you had mentioned earlier that if fasting has unique benefits, you won’t be surprised if it, uh, is gonna require these longer fasts. How can you lose muscle fasting for that 

Grant: long?

Yeah, this is an interesting area. So this is an area that’s been researched for a long time, like early starvation literature from over a hundred years ago. Some of the early literature showed that there wasn’t like substantial increase in muscle protein breakdown till after a few days of fasting, getting closer to three days of fasting.

Since then, you know, there have been, you know, have been some potential concerns. The data, I’d say is, I guess, a little bit mixed or not the exact data you wanna see to fully answer that. So I guess from a more practical perspective, I would say if gaining mass, gaining lean mass is your priority, then you probably don’t need to be doing these longer.

Fast. If you’re at a point of maintenance, and again, you’re more concerned with, um, health, you’re willing to roll the dice a little bit or deal with some discomfort to get a possible unique health benefit or benefit for longevity or so on. I think with the well-designed, uh, nutrition and resistance exercise program, even in a relatively trained individual, you could maintain even if you were doing a fast of that duration of, you know, like 24, 36 hours, even as often as like a one once a week, 24 hour fast.

I, I honestly, I think you could, this is educated guests. I haven’t seen this exact study, but I think you could, uh, maintain lean mass again, would not be consistent with like trying to optimize lean mass gains. So, you know, that’s my. 2 cents, I guess. And is 

Mike: that the frequency that you would wanna see for somebody saying, Hey, I understand speculative, I’m trying to do everything I can to live as long as I can.

Do you think once a week, 24 to 36 hours would be appropriate? 

Grant: I think that’d be reasonable. I, I generally view it just kind of for practical reasons, kinda an inverse relationship between the duration of fast and how frequently you do it. So if someone really wants to ohma, they could. Um, if you were extreme about that one meal a day, you could view this as a one hour eating window, 23 hours of fasting each day.

So if you’re eating each day, can’t get longer than that for repeated daily fasts. So, yeah, if, if someone’s wanting to do a 24 hour fast there, then there have been some studies that are relatively similar to this. We’re getting close to the realm of certain types of periodic fasting or alternate day fasting where we’d have kind of repeated with true alternative fasting, kind of repeated 36 hour fasts.

Generally that’s not great for adherence. Um, hasn’t been shown to be. Better than calorie matched kind of normal eating patterns and is generally less enjoyable. So, uh, again, in terms of like the body comp and general health marker side, we’re not necessarily recommending it there. This is again in the speculative range, but yeah, I would say maybe weekly, but the longer it is, the longer you could wait.

So, you know, some individuals really pride in, like you said, the mental challenge or they just believe there’s a benefit in these longer fasts. So they’re trying to go 48 hours and beyond. Those, I certainly wouldn’t recommend every week. I’d say spacing those out more, whether that’s like every few weeks or monthly or so on.

And again, I’m not recommending this per se, but I’d say if you are wanting to do longer fasts, the longer you go, I would say the less frequently you would need to do them and, and potentially should do them. 

Mike: Makes sense. Um, I, I see some people out there, they’re under the impression that doing a 24 hour fast once a month is gonna make a big difference.

For example, people are trying to sell other people on their protocol. They have something to sell, and so they’re, they’re also trying to manage how difficult it is and, you know, okay, can I convince people to do a 36 hour fast once a week? Eh, can I convince them to do it once a month? Uh, better 

Grant: chance. No, that’s interesting.

So definitely from the body comp side, if you think about it, you’re like, yeah, day, a whole day of fasting. Well, one a 24 hour fast could be from like 5:00 PM one day to 5:00 PM next day, then you eat a. 1500 calorie dinner and your actual energy deficit is not that large. But say you did a day of complete fasting and say your total daily energy expenditure was 3000 calories.

If you think about doing that once a month, it only takes, say, an extra a hundred calories a day of a little bit of, you know, overeating or say in the week leading up to that, you know, eating a little more the days after that. Eating a little more purely from the energy balance perspective would not take a lot to undo that fast.

Yeah, definitely. Interesting topic of conversation. You mentioned 

Mike: mTOR and that there are, I guess, two sides to consider. There’s the body comp side and then there are some of these claims. I wanted to come back to this cuz a, a lot of the health and longevity stuff will mention this. I also had autophagy on my list, but you already covered that.

Can you talk a little bit more about your thoughts on the purported importance of minimizing mTOR to maximize longevity and function? Yeah, 

Grant: I think there’s a reason that aging researchers are keyed in on this. There, there are data from other organisms to support calorie restriction, whether that’s, again, the calories itself or calories and fasting, you know, we’ll leave that aside.

To support calorie restriction, reducing mTOR activity and promoting longer lifespan, even maybe some links directly. My view just from, you know, studying physiology for a number of years, in my various degree programs, is that. Trying to have something always on or always off is probably not ideal in not really representative physiology.

So most of our pathways are, are the dimmer switch where they’re more active and less active. Also, if we get into things like circadian rhythms, there’s a natural oscillation of virtually every process in our body over predictable periods of time. So relating this back to mTOR, my view, or kind of the way I mentally reconcile, I guess sort of the aging side of things and the sports nutrition, let’s maximize mTOR, let’s, let’s get Jack’s side of things, is that you want periods of time where you strongly stimulate mTOR, you perform resistance exercise, you ingest your protein, you have this synergistic effect, strong stimulation, you’re remodeling muscle protein in beneficial way, and then you have periods of time where that process naturally comes down between meals, you’re, you’re ready for your next meal and so on.

Even if you try to get around. The processes in your body can outsmart you. So they’ve done studies where you’re continuously infusing someone with amino acids that should be simulating muscle protein synthesis. And even when you continuously infuse, at some point muscle protein synthesis will become refractory and come back down.

Um, so your body knows that the processes should, should be up at times and down at times. If we’re thinking about long-term lean mass gain, you just debunked 

Mike: BCAs . 

Grant: Yeah. Yeah. So that’s a great, yeah. If you’re, if you’re consuming BCAs between your meals, really not necessary. If you believe there, there could be, you know, benefits of having mTOR low at certain times in terms of longevity.

You might be undoing that even though again, your body will know that muscle protein synthesis can’t be just maximized at all times. Um, can’t do it. Continuously performing resistance exercise, unfortunately. 

Mike: And then unfortunately we don’t have the mouse metabolism where we would all be shredded . Yes, yes.

Eating food all day and, and absolutely jacked. 

Grant: Yeah. You fast every night and you know, you’ve lost, you know, five, 10% of your body mass. But if we’re talking about lean mass gain, this isn’t saying again, mTOR doesn’t have to be maximally stimulated all the time. Muscle protein synthesis doesn’t have to be at its ceiling all the time.

We’re saying on average over a period of time, you’ve had more muscle protein synthesis going on, um, than breakdown. But there, there are going to be these natural oscillations no matter how much you fight it. I remember way back in the day reading, I think like a muscle and. Article, you know, as early on in this as teenager and you know, some, some Jack Guy and they’re like, what, what was your secret?

What took your physique to the next level? Uh, and not, not to make any, um, moral judgements here, but someone who probably 99 I have a hundred people looking at would say, you know, potentially enhanced. And he said the thing that took his gains next level was setting an alarm for the middle of the night.

So he’d wake up and he had a huge dark peanut butter by his bed. He’d just grab a spoon, eat as many scoops of peanut butter as you can, and then go back to sleep. And he is like, I just couldn’t get all, couldn’t get all the protein I needed protein. Peanut butter is a good protein source. That’s a 

Mike: diet hack.

Just unfollow anyone who says that peanut butter’s a great so 

Grant: source of protein . But it, yeah, it was just that, that idea of like, I need constant protein. I need constant simulation of these processes. I need, you know, trick my body and did getting super jacked. So that’s kind of a rambling response, but that’s, that’s kind of how, how I view it is that our, our physiology is set for these processes to be high at times, low at times.

That’s built into our natural rhythms and I think that’s reasonable. That’s why we don’t. Infuse amino acids all day. That’s why, you know, the evidence is pointing to not needing, you know, BSA consumption between every meal. You know, you have at least three, ideally maybe four, maybe five times a day, where you’re consuming a dose of high quality protein.

They’ll maximally stimulate muscle protein synthesis. Pairing that with exercise, depending on calorie intake and other factors, can help you meet your yearly mass gain desires. And again, if someone really wants to, to go out there where it’s like, I need periods where mTOR suppressed, that’s where I go back to.

Like if I had to guess, and if this actually panned out, maybe those less frequent, longer fast, you’d get kind of like a very low level mTOR that would allow FR autophagy, I guess I didn’t make that connection, but the reduction of mTOR. Increase in some of these other sensors of low energy status like m pk, that would ultimately lead generally to upregulation of autophagy.

So that’s some of the tie-in there where people on the fasting side say, yeah, beware of protein fast. We don’t want mTOR, cuz that’s going to inhibit autophagy. 

Mike: And so if I’m hearing you correctly, you’re skeptical of interventions that are supposed to take mTOR as low as possible and, and keep it there for extended periods of time.

Like fasting. Again, it’s usually the trio, it’s protein restriction, like people who are really into it, as I’m sure you’ve seen, they’ll take periods where they’re doing a lot of fasting, they’re eating very little protein, and they are restricting their calories fairly 

Grant: heavily. Um, I would be fairly skeptical.

Now, again, the, the underlying physiology. Makes sense in the road models. If it does translate and you wanna do that periodically, you can. Now, if we’re talking about fitness people and you’re trying to balance these two things, you’ll have to make a call somewhere cuz um, it’s certainly not, not optimal, say for, for lean mask gain or maintenance to, to not eat for long periods of time.

We’re not talking about, I’m like, yeah, you, you know, you can probably maintain if you do this. But some of these recommendations are at odds. Like what we know from source nutrition, what we know. Body composition for performance. Some of that is at, certainly at odds with these recommendations, like you were just saying, of low energy, low protein, uh, and so on.

And there’s 

Mike: no evidence that I know of that a, a high protein diet, for example, is harmful to longevity. Uh, in fact is my understanding is the weight of the evidence is the opposite because it supports some of these other things like lean mass for example. And the reason I bring that up is I just, that’s usually part of the discussion is there’s this idea that eating a high protein diet is bad for your long-term health.

It might be great for your biceps, 

Grant: but Well, if it’s great for my biceps, then, you know, that’s all I need to know. , no. Uh, but no, I think you’re right. I think that’s what people would, so people on the, the fasting for longevity side with, with strong feelings on that. I think would, would recommend lower protein, but based on these pathways, cuz they’re, they’re just equating mTOR being high with bad aging, so on.

But you’re right, like we were talking about earlier with, with maintenance of lean mass as you age and function and all that, certainly, um, high higher overall protein, higher total dose protein is, uh, important for maintaining lean mass, say gaining lean mass, maintaining muscle function and so on. So yeah, I would tend to put more weight in those areas.

We have established more concretely, again, especially in the context of what you said, of active individual, nutritious diet, all these things. I’m just not super optimistic about the, the added benefit fasting there. And in some cases, like we’re talking about here, maybe with aging. I, I would feel like it’s the opposite.

Yeah. Makes a 

Mike: lot of sense. I mean, that’s been something I I, I’ve been saying for a while, going back even 10 years now, people have been asking about fasting for that long. It’s only gained pop popularity really in the last decade. Um, but is that point of, okay, if we see some interesting things in obese, sedentary individuals with type two diabetes, that doesn’t mean that we’re going to see similar benefits to insulin sensitivity.

For example, the person asking me who is healthy, active, et cetera, et cetera. And until there’s, there’s more research that is relevant to guys like us and to women who are fit to people who are doing the things that we know work. Again, I, I’m not too excited about some of the claims that people are currently making and, and usually to sell stuff I, if nothing else, to sell themselves.

Some of these people, Some people, they’ll look at them and say, oh, well, they don’t have anything to sell. Well, not yet. Right now they’re selling themselves. They’re building a brand, and that’s worth a lot of money. Once you have a big enough personal brand, you can monetize that in many ways. So just something for people listening to keep in mind, because somebody doesn’t even have a book to sell, doesn’t mean that they are not going to be selling something at some point, or they are not monetizing their personal brand in ways that you are not 

Grant: seeing.

Yeah. Let me just throw random stuff out there. So I’ll say, given all this, I actually like fasting. I don’t fast all the time, but I actually like it. I think it’s cool. I honestly, I hope I’m wrong. I hope we get the data at some point where it’s like, yeah, you know what? Turns out your 16 hour daily fast is doing great things for you.

That’s all you need. Or a 24 hour fast or one small. I hope I’m wrong. I, so I’ll say personally, it’s interesting, this last three months or so have been the first time I’ve consistently eaten breakfast in probably nearly a decade. Um, so for nearly a decade I would say I did time restricted eating, varying in intensity.

If I had times when I was trying to, to gain mass, um, it was very, you know, where you could look at it, say like, is that really time restricted eating? Maybe like a 12 hour eating window. Something that allows people to do naturally in terms of maintenance or trying to lean out. I would push up to, probably the most fasting I’ve done at any point would be daily, six to eight hour window with like a weekly 24 hour fast run in.

And that would be like, um, cuz cuz I didn’t mind it. Like, when I’m here at work, I’m just like mentally consumed with who I’m doing and I could easily like not, not eat till later in the day. Um, but there’d be peers where I’m very intentionally trying to lean out during those times. I, uh, increase my protein intake, you know, to, to a relatively high level, maintain resistance, exercise, all that.

But I’ll say for these last three months, just cuz of my schedule and like convenience, I’ve, I’ve transitioned to. Breakfast, like a very, essentially protein only, but like protein centric lunch. And then kinda like you were saying, a little bit more of a generous, um, dinner. Sort of similar to you. The lighter eating during the day is helpful to not, not slow me down, uh, you know, as I’m working.

So yeah, I’m, I’m totally, I have no problem with people who, who love fasting. I feel like I probably come across as like, despite the fact we study this as critical of fasting more than really buying into everything about fasting, I think it’d be great for individuals. I just don’t think the benefit should be overstated or things that we’ve seen in model organisms should be directly applied to humans without caveats related to the duration of the fasting.

What’s realistic to expect, what we can actually track, which is fairly. Limited right now, I’d say in this longevity realm in humans. Yeah. I,  

Mike: I think you’ve, uh, given a very fair assessment of, you don’t sound like a fasting basher to me, and, and I myself have, have done the exact same thing for periods of time just to try it for fun.

All right, I’ll, I’ll do, I think maybe the first I tried was the lean gains approach, which I think was, what is it? 18 hours? Uh, 16, 18 hours of fasting. And then the remaining is you’re eating window, skipping breakfast, basically. And I did that for a while and I mean, sure it was fine, but I just like having, you know, I’ll have a protein shake and a banana, like that’s my breakfast.

Then I also like to, I have a, a cappuccino in the morning and I want the milk in it. I don’t want just the espresso. Espresso’s good, but it’s better with the milk. So, you know, there are reasons, there are reasons why I don’t do it, but I understand. Why some people like it and it can work quite well for some people.

It can fit their lifestyle, it can just fit their natural kind of appetite rhythms. So no, I think that again, that you’ve, you’ve been very fair. And is there anything else that you haven’t mentioned yet that you wanted to mention or something that I should have asked you that I haven’t asked you before we wrap up?

Grant: Not immediately off the top of my head. I’ll, I’ll give the disclaimer again that, you know, I’ve done a number of fasting related studies, largely in the realm of body composition performance, um, some health markers. I have a lot of great collaborators to, to acknowledge, uh, for that. Um, some in Italy, Antonio Pioli and Tatiana Moro and others here domestically.

But, so I’ll say this longevity area, I’m sure, you know, someone who has studied longevity for their whole life could look at this and be like, Hmm, you’re taking some liberty, simplifying things. But you know, that’s part of science communication. We try to give the, the nuances and. Caveats and clarifications, but, uh, at some point you have, you know, whoever’s listening has to be able to understand what you’re saying.

So, uh, this is my rambling way of saying no, I don’t think there’s anything else in particular that, that I need to add at this point. Okay. 

Mike: Cool. Well, um, this was a great discussion. As usual, why don’t we wrap up quickly with, uh, where people can find you and find your work if they want to check out any of the research that you’ve done or anything else you want them to know about.

Grant: Yeah, absolutely. So I’d probably share the most regular updates on, um, Instagram, and my handle is just grant underscore tinsley underscore PhD. And then I also have a website where you can find more information about our research team and some of the projects I’ve been involved with. And that’s just, um, my name, grant

Mike: Cool. Yeah. And those, those links will be in the show notes, but for people who don’t look at show notes. There you go. Awesome. Thank you. Yeah. Yeah. Um, well this was great. Again, grant, thanks for doing it and I look forward to the next one. 

Grant: Thanks.  

Mike: Well, I hope you liked this episode. I hope you found it helpful, and if you did subscribe to the show because it makes sure that you don’t miss new episodes.

And it also helps me because it increases the rankings of the show a little bit, which of course then makes it a little bit more easily found by other people who may like it just as much as you. And if you didn’t like something about this episode or about the show in general, or if you have, uh, ideas or suggestions or just feedback to share, shoot me an email, mike muscle for, muscle f o r, and let me know what I could do better or just, uh, what your thoughts are about maybe what you’d like to see me do in the future.

I read everything myself. I’m always looking for new ideas and constructive feedback. So thanks again for listening to this episode, and I hope to hear from you soon.

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