Dr. Pastore interviews Dr. Grant Tinsley, assistant professor of exercise physiology at Texas Tech University. In this conversation, they discuss the science behind intermittent fasting and its effects on modulating body composition and performance.
Dr. Pastore: Welcome to another episode of the Modus Movement Podcast. I'm your host, Dr. Robert Pastore. Today is a very interesting topic. We're going to be talking about fasting for active individuals, and my guest today is Dr. Grant Tinsley. Dr. Grant Tinsley is an assistant professor of exercise physiology at Texas Tech University. He graduated summa cum laude with degrees in physiology and nutritional sciences from Oklahoma State University. He then completed his master’s degree in biomedical sciences at Colorado State University, and his PhD in kinesiology and exercise nutrition at Baylor University. Dr. Tinsley is also a certified sports nutritionist and certified strength and conditioning specialist.
Dr. Tinsley's research focuses on the impact of diet, exercise and supplementation on human body composition, athletic performance and health. One of his particular research interests is evaluating intermittent fasting programs as a method to improve body composition and health. He also researches optimal assessment methodology for body composition. The overall goal of his research is to provide new information about the impact of lifestyle interventions on body composition and health in humans.
I'm also honored to call Dr. Tinsley a personal friend. Dr. Tinsley, it is a pleasure to have you on my podcast. Thank you so much for joining me today.
Dr. Tinsley: Absolutely. Thank you for the kind words, and I'm thrilled to be chatting with you today.
Dr. Pastore: It's such a pleasure, so here's where I'd like to just jump right in to it. There's so much information on the internet about intermittent fasting, and I definitely see you as someone who's an expert in the field, so I was hoping, Dr. Tinsley, could you please clarify and define what that actually is?
Dr. Tinsley: Yes. I think clarify is a great word, because there is a lot of confusion, and we know this is something really popular. If you talk to most health conscious individuals, they'll have heard of intermittent fasting, and they might even think they have a really tight definition on it, but as you kind of discuss with them further, there's a lot of confusion.
I'll start out by saying intermittent fasting is really a broad term, kind of an umbrella term, and there's specific types of intermittent fasting and we'll get into some of those later, I'm sure, but there are some commonalities between these different forms of intermittent fasting. The major one is that they all implement regularly occurring fasts that are longer than your typical overnight fast. And even there, we're getting into murky waters already, because an overnight fast for different individuals could vary based on how much sleep you get or whether you eat breakfast right when you wake up, whether you eat breakfast at all, et cetera.
But all these intermittent fasting programs somehow extend that, what we view as kind of the normal duration overnight fast. Another way to view this is that you'd have kind of a drastic reduction in energy intake, often meaning no energy intake, interspersed with periods of time where you eat relatively normally. This sometimes relates to a systematic reduction in meal frequency, which is a little strange to think about, because for many years, there were recommendations to increase meal frequency and eat every couple hours to kind of stoke your metabolism. So this is, in some sense, is swinging in the opposite direction.
The one other thing I'll say to kind of define the programs in general is that intermittent fasting doesn't say anything per se about what you eat. It's much more of a timing strategy, so it's very possible and very common to combine intermittent fasting with other dietary approaches. So for example, if someone, if a low carb diet works best for someone, you could combine a low carb diet when you are eating in the context of an intermittent fasting program. Or low fat diet, keto, anything. We're not saying anything yet about the content of the diet, and we know that matters, but intermittent fasting is really addressing the timing of eating.
Dr. Pastore: Okay. Very interesting. Now, please correct me if I'm wrong here, but I believe there's data on the holy month of Ramadan that has helped provide some solid research before anybody else was really doing clinical trials. Can you shed some light on that?
Dr. Tinsley: Yeah. I'm really glad you made that connection, because a lot of people take about intermittent fasting and they never even address Ramadan, but it's interesting. There is a very large proportion of the world population who are Muslim, it's estimated over 90% of Muslims actually observe fasting to some extent during Ramadan, which is really incredible. Just for anyone that's not familiar, fasting during Ramadan normally consists of eating only while it's dark outside. So you essentially fast from food during the daylight hours, then eat at night time
There's actually quite a bit of research on athletes during the holy month of Ramadan, and the results are really mixed, and there's some good reasons for why the results are mixed, so I wanna just briefly address that.
Dr. Pastore: Please.
Dr. Tinsley: In my mind, there's some pretty substantial limitations to this research, and that's not anyone's fault. It's just kind of the nature of what's available. So the biggest thing I want to emphasize to start is that research during the month of Ramadan is typically observational, so what happens is researchers, well intentioned researchers say, “This is this really interesting eating program. Everyone's going on this for four weeks. I have access to this population of athletes. I'm gonna study what happens during these four weeks.”f So it's observational. These individuals aren't randomly assigned to fasting or to a control diet. Everyone's just kind of going through the same program, and they were going through that anyways. The researchers just decided to jump in and observe what's happening.
So because of that, that means there's typically not a control group that's not observing the Ramadan. One other really notable factor is that there are tons of lifestyle changes during this month, so it's not just the time of eating, but there's often feasting after sunset, so when the sun has gone down, it's dark. There are different social interactions, different food choices, layout of the feast both at night and whether or not someone decides to get up before the sun rises to eat can lead to sleep deprivation, so individuals often sleep less during the month of Ramadan.
One other note. It's so fascinating, multi faceted, but Ramadan is actually set according to lunar calendar, meaning that it's not at the same time of year each year. It advances, I believe, by 11 days or so per year. So what this means is that even at a given geographical location, the number of daylight hours are not the same each year, and then if you also take into account different geographical locations, you're not necessarily comparing apples to apples if you're looking at research on Ramadan intermittent fasting, because someone might have only an eight hour fast, a short amount of daylight, and someone else might have a 14 hour fast in a different year or at a different geographical location.
So for all those reasons, it shouldn't be a surprise that the actual results on athletes are really mixed, because there's so many factors going into it, and those often aren't clearly outlined in the research articles. One of the things that's amazing to me is there's actually been mixed results on whether or not calorie intake decreases in athletes during Ramadan. In some studies, energy intake, calorie intake has decreased. In other studies, hasn't changed at all, and in some, it's actually increased by up to 20%, and the researchers believe this is due to the fasting and the social interactions where you haven't eaten all day, the sun has set, you're feasting with your families and you can end up eating so much that you actually are hypercaloric for the day, even though you would assume that someone was eating fewer calories during Ramadan.
Without going into all the gory detail, in terms of the major results, really mixed for body composition in terms of fat mass and lean mass. Some studies report fat reduction in athletes, others report no change. Really same results for lean mass, some individuals lose lean mass, some don't. Performance, it really seems to depend on the type of performance, as well as these other factors I mentioned. If an athlete maintains their energy intake, if they maintain fluid balance, their sleep and their overall training volume, they can maintain their performance very well, particularly in shorter duration events, in kind of strength or anaerobic performance events.
Where you see the bigger problems are when people can't maintain their training volume, they're sleep deprived, they might be dehydrated or hypohydrated, because as a side note, strict observance to Ramadan fasting would disallow fluid intake also during daylight hours. So when you get into endurance events, especially those longer, say longer than 10 minute events, you do see some performance decrements. So, I guess to wrap it all up, lots of factors saying that comparing one study on Ramadan intermittent fasting, it's not easy to compare to another study, and because of that, we really have mixed results.
Dr. Pastore: Yeah, I can definitely understand that and I didn't even put all that together, so I really appreciate that, doc. That's excellent. Excellent summary, but I'm so grateful we have that data. I think it was a real great starting point to have some of that science published.
Dr. Tinsley: Absolutely.
Dr. Pastore: Also there's ... When I hear the term intermittent fasting, I'm thinking of all the different published researchers out there and I know you gave us a great little summary there, but there's also ... Would you say there's different nomenclatures associated with it, right? So there's time restricted feeding, there's alternate day fasting as you were discussing. Is there a certain form that you think is better than another form, or is leading the charge with regard to research under the umbrella of intermittent fasting?
Dr. Tinsley: Yeah, that's a great and really interesting question. Yeah, just first so everyone's on the same page, like I mentioned, intermittent fasting's kind of the umbrella term. Some people argue with this, but what I see as the main forms, first, time restricted feeding, so that's essentially where generally, you follow the same eating schedule every day, and you're just restricting all your food intake to a single period of time, usually four to eight hours in duration. So for example, it's really common right now, really popular to eat all your calendars in an eight hour feeding period every time, meaning that the other 16 hours per 24 hours, you're fasting. So that's time restricted feeding.
Alternate day fasting, what we call true alternate day fasting, just means you eat every other day. So Monday you eat normally, Tuesday you don't eat. Wednesday you eat normally, Thursday you don't eat. As you just kind of alluded to, that's difficult, so really what's more common is alternate day modified fasting, where you would eat normally one day, then eat a very small amount of calories the next day, generally around 25% of your weight maintenance needs, typically consumed as a single meal. So this would often be eating just lunch, say on Tuesday, and Wednesday, back to normal eating. Thursday, you're eating just lunch again, and you kind of alternate indefinitely.
One other type, which can be called whole day fasting or periodic fasting, is where you don't fast as often, but you fast for a little bit longer. So this is often one to two 24 hour fasts per week, or maybe even a 36 hour fast. 24 hour fast sounds like a long time, but really, if you're doing a 24 hour fast, there's never a calendar day where you're not eating. So you could, say, fast from 6:00 PM on Wednesday to 6:00 PM on Thursday, so that's a 24 hour fast, but you can still eat dinner on Thursday. So that's kind of an interesting form.
In terms of the research, there has been a lot on alternate day fasting, specifically the modified version where you do allow the lunch in take on the fast, so called fasting days. Lot of research on that. I would say in practice, time restricted feeding is quite a bit more common. Some people view the Ramadan intermittent fasting we just discussed as a form of time restricted feeding, because you're restricting your eating window just based on daylight, essentially. The periodic fasting, and you can even see, as I describe these, you could get into situations where you design an intermittent fasting program, you're like, which one is, which category does this actually fall in to? So then you have to kind of revert back to just the broad principles we know are in place, like the fast longer than an overnight fast.
I'd say at present there's a lot of good research on alternate day fasting. Starting to be a few more studies on time restricted feeding, even studies looking at when you place the feeding window in relationship to circadian rhythms, so do you feed earlier in the day, do you feed later on the day?
Dr. Pastore: Fascinating.
Dr. Tinsley: I'll try and keep my answer there, or else I'll just ramble on.
Dr. Pastore: No, that is awesome. I love that. That, I definitely want to ... We should touch upon that in a little bit, but I'm curious to know if you think time restricted feeding is gaining popularity in sports and fitness in general?
Dr. Tinsley: Yeah, I think it is, and I have a little bit of quantitative information on that I'll share. Not, yeah, just limited information. I do think it's gaining popularity, and I think ... One thing I want to just say at the outset is that I think the applications of time restricted feeding, you should definitely, of course, consider the individual, but also consider the level of athlete. So time restricted feeding, for example, is very popular in the general active population. I haven't seen it permeate into high level athletes quite as much, and we can get into it later, maybe, but I would ... Well, I'll just get into it now. I would certainly never recommend that all high level athletes perform TRF. In fact, I'd probably recommend that most don't.
When you're at a very high level, elite athletes, and you know this, you've worked with elite athletes for many years, you have to optimize everything. Even sacrificing a little bit of recovery or a little bit of performance because of not following optimal eating, that's their livelihood. So that's a different scenario than myself or other people who are generally active, who they love fitness, they love exercise, they wanna be healthy, but my livelihood isn't dependent on peak performance or peak body comp or anything like that. That's kind of a caveat.
In terms of popularity of TRF, the metrics I have to demonstrate its popularity are really based on two studies we've done in this area that I just want to, if you'll indulge me, I'll briefly mention. I know we might get into details of the studies later, but currently there are only two studies of any form of intermittent fasting. In this case, time restricted feeding, combined with weight training.
So my excellent collaborators and I have published these two articles. Really, looking at the interest these two articles have generated is really what's kind of tuned me in to just how interested people are. For example, our 2016 time restricted feeding article just surpassed 100,000 reads last week on the journal's website, and this is in just over two years. You know, some individuals, I'm glad you appreciate that, that are used to YouTube views or blog articles, this and that. 100,000 may not sound like a ton, but for a journal article, that's kind of astronomical. Altmetric, which is a website that tracks these things, puts this article, after about two years, at number 4,000 or so in terms of popularity out of over 12 million research articles, and that places it in the 99th percentile for articles of all ages, even though it's only two years old.
Our other article was, actually, just won this last summer, the 2017 best paper of the year award for the journal it's published in, the European Journal of Sports Science. It's already the 6th most read article in the history of that journal, which has been around for about 20 years. I say that just to say that researchers, practitioners, and then just the general active population, who are trying to keep a little bit of a beat on current research, they seem to be really interested and really receptive to this. So those are kind of the metrics I have that tell me, yeah, I think people are really interested in this topic.
Dr. Pastore: And now, I'm hoping anyone who's listening understands, this is exactly why I wanted you on the show. This really covers everything, and you know, if you don't mind, I'd like to segue into that paper, because that was on my mind, and this is the paper I'm referring to. The first one you mentioned, which is in the Journal of Translational Medicine back in 2006, which was on eight weeks of time restricted feeding on basal metabolism, maximal strength, body composition, inflammation, cardiovascular risk factors, resistance trained males. Can we start with why you decided to pursue this study? Because I can understand the 100,000 people researching it. You're in that top percentile. That wasn't there. There was no paper before your paper that really was looking at this. So what was the impetus for you to wake up, get your team together and go, "We're doing this?"
Dr. Tinsley: Yeah, that's a great question, so going into my PhD program, I definitely had an interest in modulating body composition, so specifically how do we increase muscle, how do we decrease fat mass? How do we improve performance? All these things.
My post doctoral mentor, Dr. Paul La Bounty, had actually been the first author on a big position stand on meal frequency put out by the International Society of Sports Nutrition. So it was looking at meal frequency and implications for active individuals. Kind of one of their main conclusions, and this reflects the time it came out, was that you don't have to eat every couple hours to stoke the metabolic fire as some people previously thought. As we were discussing that and kind of how this was interesting and how that went against what we heard for years in lay articles, we started wondering about the opposite end of the spectrum. What if you reduce meal frequency? Would that work for athletes? Do we compromise skeletal muscle? Are we gonna start catabolizing muscle protein? Could performance be maintained?
We had a lot of questions there and had seen some really preliminary research on intermittent fasting, but largely in a sedentary, obese population, which was not necessarily reflective of the individuals we were most interested in. From working with Dr. La Bounty, I began to get really interested in this and I really just kind of asked for permission to pursue this project on my own and he said, “Yeah, go for it. I'm interested in this, too. Feel free to design a study and get started.”
Around the same time, at the American College of Sports Medicine conference in 2015, I was perusing through the hundreds of pages of abstracts before the conference, seeing what caught my eye, and I saw someone was actually presenting research on time restrictive feeding and resistance training, and I was really fascinated by that. It was an incredible researcher from Italy named Antonio Paoli. He's been researching the ketogenic diet since way before it was mainstream popular. Brilliant guy. I planned the whole conference around being able to go to his session and talk to him about this, and I said, “Hey, I'm doing a study like this, too.” We exchanged information, really hit it off, and that's when we started collaborating.
These two studies we're about to talk about were, one was conducted in Italy, one was conducted here in Texas, and these were really a result of our collaboration together and I'm really thankful for Antonio and his lab over there. The article you're referring to, the 2016 Journal of Translational Medicine, that was the one conducted over in Italy, specifically at the University of Padova, through Antonio Paoli's lab.
So yeah, that was kind of the evolution. Meal frequency, body composition, getting connected with the right people at the right time.
Dr. Pastore: Wow. That's incredible. And I love that, going after and seeking out your researcher that you really want to study with or learn from, and here it turned into a beautiful collaboration. Can you talk a little bit more about this study? Can you review just some of the highlights, however you feel, as deep as you wanna go? Regarding the methods and what was inclusion and exclusion criteria, because we're all so fascinated in this time restricted feeding and physical training. It goes against everything I was focusing on with my, working with my pros, right? And then you think of the mantra of people who maybe are not professional athletes, but their livelihood depends on their physicality, and pardon me, but I'm thinking of Dwayne The Rock Johnson, who I think has a mantra, just one more bite. He's doing the exact opposite. He's doing excessive feeding in any moment of time versus time restricted feeding, and those are the tools he gave Hugh Jackman to get into the Wolverine size.
Yeah, so this paper fascinated me since the first time I read it, so if you wouldn't mind going over all the data sets, however you're comfortable, please.
Dr. Tinsley: Yeah, absolutely. Celebrity side note, since you mentioned that, that's funny, is yeah, The Rock is a huge fan of feeding. Terry Crews is a big fan of intermittent fasting-
Dr. Pastore: Yeah.
Dr. Tinsley: Two guys with very muscular physiques-
Dr. Pastore: Exactly.
Dr. Tinsley: Yeah, so just giving the big picture on this. The purpose, really here, was looking at physiological effects of time restricted feeding when combined with resistance training, so weight training. This population was highly trained. There are some studies, including some I've conducted, and maybe the next one we'll discuss, that use kind of recreational active individuals, but not highly trained individuals. This was not one of those studies, so most of these participants were really natural bodybuilders. They all had at least five years of continuous resistance training experience of at least three to five days a week. They were all lifelong steroid free athletes. Didn't have any clinical or medical problems that could be aggravated by the study.
If you look at the individuals we've got, these were males, average age around 30, BMI in the overweight range, around 27, but combined with a really low body fat, so around 13% body fat via DEXA, dual energy x-ray absorptiometry on average. That combination of overweight BMI and low body fat tells you these were really muscular individuals.
Dr. Pastore: Fit people.
Dr. Tinsley: So these individuals were randomly assigned to one of two groups, so one was a control diet, one was time restricted feeding. Something that's really interesting about this is both groups maintained the content of their diet, of their habitual diet, throughout the study. Coming into the study, all the individuals were consuming, on average, 3,000 calories a day. Pretty high protein diet, about 1.9 grams per kilogram per day, and around four and a half grams per kilogram of carbohydrate a day, which is reasonable for this strength and power range.
So they actually maintain that throughout the study. They also, actually, both groups during the study had the same male frequency. We were controlling meal frequency, controlling the content of the diet, really the only thing that changed was that the timing of the feeding. So the control group consumed one meal at 8:00 AM, one meal at 1:00 PM, so morning meal, midday meal, and then a meal at 8:00 PM, kind of late dinner, and the only other time they eat was consuming whey protein immediately after their workout.
The time restricted feeding group had the same three meals, but they were at 1:00 PM, 4:00 PM, and 8:00 PM, and they had an hour to eat each meal, so they ended up with an eight hour feeding period, starting from midday until the mid evening, whereas the control group had their feeding spread out throughout the whole day.
Throughout the study, both groups were meeting with the dietician to review everything, make sure they were complying, make sure they didn't have any questions. Both groups followed those meal frequencies, and then again, with the addition of protein post training, and then they both did an identical resistance training program for eight weeks, and this was directly supervised by the study personnel, which is a great strength of the study.
So let's see, I won't go into all the details on the resistance training program, but it was ... Yeah, the details of that are in the article, but point being both groups did the identical resistance training program and what we were really looking at, a few major outcomes, so body composition, so lean mass, fat mass. We were looking at muscular strength and performance, and then a variety of physiological markers. We won't go into all of them, but three main categories we looked at were blood lipids, hormones, notably testosterone, the the major male, so to speak, anabolic hormone, and then inflammatory markers, as well.
Would you like me to go ahead and jump into results or do you have any questions about that-
Dr. Pastore: Yeah, I mean I'm definitely, I'd love to hear the results, but I am curious about if truncated testosterone over long enough period of time would really have the detrimental effect on skeletal health, skeletal muscle health, and skeletal health, that we've been seeing in isolated, controlled experiments, right? We've even seen males that have hypogonadism are more at risk for osteopenia and perhaps osteoporosis. I've met males in their 60s and early 70s that were being treated with Fosamax, and by the same token, were perhaps on Andro gel by their endocrinologist.
So that has always fascinated me. If IF in any way alters hormone status over the long haul.
Dr. Tinsley: Yeah, absolutely, so that's something that's really interesting and yeah, so to give context to that, in this study, there were no changes in lean mass over the eight weeks. And I'll relate this to the testosterone in a second, which really could be viewed as a good result. In a highly trained population, you wouldn't expect that a simple eight week program would dramatically increase their muscle mass. Maybe if they were untrained or lightly trained.
So no changes in lean mass, but yeah, what you're referring to, one of the interesting results is that there was actually a drop in testosterone in the time restricted feeding group. This came also with a reduction in fat mass, so time restricted feeding group decreased fat mass, control group didn't. But that reduction in testosterone definitely raised some eyebrows, so just to give you the value, the pre study testosterone value in the TRF group was 21 nanomoles per liter. The post testing was 17 nanomoles per liter, so decrease. The normal range that I found was 10 to 39 nanomoles per liter, so definitely within the normal range still, but it did significantly decrease.
It's pretty debated on if changes in testosterone within the normal range are really physiologically relevant. We know if you're outside of the physiological range, or the very low end, or in individuals who had exogenously administered anabolic steroids, that that certainly has impacts on skeletal muscle. One thing that's interesting, and this probably isn't ... Even people that were familiar with these articles may not be aware of this. We actually, within this last year, published a abstract and we're preparing full manuscript that's actually a continuation of this study, so this was an eight week study, but this continued on, actually for a year. So I can actually provide you with some new information here on the long term effects.
The reduction in testosterone was still present after a year, and there actually was a reduction in fat free mass after a year of following time restricted feeding, so there was a significant decrease in fat mass, just like there was during the first eight weeks, and that was maintained throughout the whole year. Reduced fat, but also reduced fat free mass by I believe a kilogram and a half or so. Testosterone was lower. The interesting thing is performance was not impacted, it was maintained. So there was a reduction in testosterone, slight reduction in lean mass, but performance was maintained, so this might come to one of those trade offs that is this worth it? Is it worth sacrificing a little bit of lean mass to maintain fat loss in an already lean individual over the course of a year, or is this something where it's like no, that's not acceptable, and in that case then maybe time restricted feeding wouldn't be the right choice.
One caveat here is that over the course of the whole year, even though they had maintained their calorie intake during the first eight weeks, the individuals in the time restricted feeding group did spontaneously decrease their calorie intake, so this is true in a lot of research, but it ends up being a little difficult to isolate the effects of calorie restriction versus the actual fasting.
Dr. Pastore: Fascinating. And I know this isn't published yet, so please forgive me that I'm asking. Did the testosterone levels drop into a clinically deficient range on average, or did they remain within a normal range but just decrease?
Dr. Tinsley: Yeah, great question. I'm fairly confident they were still in the normal range. I don't have the full data in front of me. And we did-
Dr. Pastore: Of course, I'm sorry.
Dr. Tinsley: Data in the abstract, but I believe they were still within the normal range, and I think ... Well, actually won't come out next time I talk-
Dr. Pastore: Any skeletal health analysis looking at bone structure? I'm curious. DEXA scan that included bone health?
Dr. Tinsley: Yeah, so that's something we're interested in for some secondary analysis. This kind of primary analysis we did for the abstract largely focused on the body composition and hormone markers, but that's definitely something we'd like to look at since we do have access to DEXA scans, and make sure there were no untoward effects on-
Dr. Pastore: Yeah, that'd be so good to see. Right now I'm thinking, boy I would love to see an undercarboxylated osteocalcin, just to see if there's a potential risk for a fracture that may pop up before there's even a major change in DEXA, but wow, that's great stuff. I will wait for that paper, my friend, sure I'll have one of the first copies once it gets...
Dr. Tinsley: Of course, of course.
Dr. Pastore: ...published. I kid you, I kid you. So if you don't mind, I'd love to segue to your other brilliant work, and this was the study that you mentioned that was published in the European Journal of Sports Science, titled Time Restricted Feeding in Young Men Performing Resistance Training, and this was a randomized controlled trial. So if you wouldn't mind, Dr. Tinsley, could you walk us through that study as well, as you did the last one so wonderfully? It would be great for our listening audience, please.
Dr. Tinsley: Absolutely, and there were quite a few similarities between the two, so I'll kind of emphasize the differences, just so we see what we're dealing with here. In this study, in contrast to the previous study, this study used recreationally active individuals, so these were more novice individuals. These were males, again. So they're generally active, but didn't have the extensive resistance training background the previous individuals had.
So essentially what that means is we were expecting some lean mass gain, and we could kind of evaluate whether or not this time restricted feeding program would attenuate or reduce that lean mass gain in any way. The time restricted feeding program itself was a little bit different, so as you know, there's certainly good research on pre and post-exercise nutrition being important, and that's something I didn't mention in the previous study, but individuals were not exercising fasted, so they ate before they worked out. They ate after they worked out. We're not trying to advocate for fasted training here, we're still trying to follow best practices in terms of pre and post exercise nutrition. And that was true in this current study, also.
So in this current study, we actually allowed unrestricted food intake all day on the three days where individuals performed resistance training. Then, on their four rest days, where they weren't actually performing exercise training, we had them consume all their calories in just a four hour period of time. It was around 4:00 to 8:00 PM. So this was a little more challenging, because it was a 20 hour fast instead of the 16 hour fast. We were looking at some similar variables. We had some limitations here. This was a unfunded study. This was really just a labor of love. I just wanted to do this study on the side.
We didn't have the resources to look at all the physiological markers that we looked at in the study conducted in Italy, but we did look at body composition with DEXA and we looked at hypertrophy of individual muscles with ultrasounds. We looked at the biceps brachii muscle and rectus femoris muscle, and then we looked at muscular performance, so one repetition maximums and maximal strength, as well as muscular endurance via tests of repetitions to failure.
Similar to the previous study, there were three exercise sessions per week. Our participants were, like I mentioned, not quite as trained, didn't have quite as ... They had good body composition, but not quite as ... more elite, as the previous study we discussed. Jumping right to the results, interesting thing here. The difference in body weight wasn't significant, but on average, the TRF group lost about a kilogram of body weight, while the normal diet group gained about three kilograms of body weight, and that was also reflected in lean soft tissue, so the TRF group had no change in lean soft tissue. It was completely maintained, so lean mass, but the normal diet group gained almost two and a half kilograms of lean mass.
Kind of interesting result, we did see some attenuation of lean mass gain with time restricted feeding. Not significant, but normal diet group gained a little bit of a fat mass. TRF group lost a little bit of fat mass, but really, main kind of result there was the apparent attenuation of lean mass gain. One side interesting note on that is that performance didn't differ, so over the course of the eight weeks, this didn't translate into differences in performance. Both groups substantially improved performance, and that's what we'd expect when we took relatively untrained individuals and put them on a program.
But kind of the thing that came out as we looked at this and looked through dietary records is that the TRF group had really self selected a lower protein intake than the normal diet group, so the TRF group was consuming about one gram per kilogram protein, which is just barely above the RDA, which is pretty well known to be suboptimal for active individuals, whereas the normal diet group was consuming almost a gram and a half of protein per kilogram of body weight per day. So quite a bit higher protein and closer up to our recommended range.
Dr. Pastore: Yeah. Wow. That's interesting. So that, I guess that would explain one component. What stuck out, for me, was the hindered hypotrophic adaptation to resistance training and reduced protein intake, that just makes sense in the time restricted feeding group, so would you believe ... Do you believe it was more of a truncated protein intake that resulted in that deficit to resistance training in that side? That arm of the study?
Dr. Tinsley: I think it was. I think that had to have been, my opinion would be that's one of the bigger factors. The duration of fasting was also longer, so maybe the four hour feeding, maybe that was too short. You know, maybe eight hours of feeding's okay, but honestly, the protein is a big thing, and honestly, that's something a lot of readers criticize, like why didn't you control protein? My answer to that would be we wanted a study that was generalizable. We're essentially saying, “What happens when you give someone the instructions to eat this way?” We're just giving them instructions. What happens?
You know, in a laboratory setting, we could control and manipulate everything, and there's some studies where you do that, but in this study, we're saying, “What happens if we set them up with this program?” And honestly, this is how many individuals would approach time restricted feeding. They're like, “Oh, I just eat during these hours.” We had them do that, and this study essentially shows us if they're doing that, they might self select a protein intake that's too low, so you need to be particularly aware if you're an active individual doing time restricted feeding, you need to be extra aware of your protein intake.
Dr. Pastore: That's a great point. That's a really great point, and look, I def ... I have to, everybody who listens to the podcast and hears me talk about my time at Eastern Michigan University, it wasn't brainwashing. It was proper scientific analysis that I really am in favor of and was educated towards a higher protein intake, particularly when I took that into practice in working with professional athletes. Anyone whose life depended on, how they made their living depended on their physicality and their performance was a 2.0 gram per kilogram of body weight individual for me as a point of reference. And of course, everybody's biochemically unique, and that was really how I was taught in sports nutrition.
Of course, I know the point eight, but what we're seeing, and if I could segue to another paper, Dr. Tinsley, is I've been extremely interested in nitrogen balance and prevention of sarcopenia. Sarcopenia is horrible. It's one of the risk factors for hip fracture. Hip fracture is one of the major increasers of all cause mortality. I've met people that fractured a hip that were young and fit cycling through Central Park, and it's just a horrendous thing to have transpire, so when we lose our musculature, and we're already facing that. Me at 49 years old, you know, it's a slippery slope down hill if I were to eat a lower protein intake, so what I'm alluding to is there was an editorial published in the November issue of the American Journal of Clinical Nutrition by Daly and Nelson and they discuss what's optimal protein for a population of adults? And they reference the 2015 study in the Journal of Nutrition that amino acid oxidation indicates that recommended daily protein intake should be around 30% higher, or more, than the current RDA recommendation for older people.
And that's the way, again, I was trained. I had a professor that would cross off the text book reference ranges and make sure he put his bold red, but based on DEXA scan analysis. Based on military studies. Based on aging population analysis. That professor is one of the greatest professors I ever had in my life. His name is Dr. John Carbone. Brilliant man, did his PhD in nutritional biochemistry at UCONN. Super bright guy and I appreciate his protein knowledge.
So I'd love to know your opinion on, and I appreciate your saying what you saw in your research study, and I accept the way you set up your study. I think it was brilliant, and that's the way it should be done. We have to bring research to real world understanding and see what people do with it, but do you have an opinion on aging and protein intake, outside of even just intermittent fasting or controlled calories?
Dr. Tinsley: Yeah, absolutely. I am right with you and with your professor. I absolutely agree, it should be higher. I think there's great research to support that, I mean there are so many researchers doing great work in this area. Stu Phillips at McMaster University in Canada, continually puts out some great stuff on this, and in my skeletal muscle physiology graduate class I teach, we talk about this all time. I'm teaching that now, so my students are probably sick of hearing of this. One of the factors that stands out to me that relates to this is that the idea of anabolic resistance in the elderly, so for the same dose of protein, the elderly individual gets a lesser anabolic response. So lesser stimulation of these anabolic signaling pathways within the muscle, lesser muscle protein synthesis response, ultimately just a harder time shifting towards a positive muscle protein balance.
So, absolutely agree. The individual doses need to be higher. The overall protein intake needs to be higher. I think there's good data on that, and I hope that trickles, eventually, to the formal recommendations, though I feel like the research has been pointing that direction in quite a while, and some individuals are hesitant to push that way, but yeah, like you mentioned, two grams per kilogram, I hear that a lot. I know the International Society of Sports Nutrition recently put out a new protein position stand and I think they recommended 1.4 to 2 grams per kilogram, in that range, for active individuals.
And for elderly or elderly active, kind of a combination, yeah. I think, absolutely, it should be higher. One side note on that, which I think is always interesting, is the acceptable daily macronutrient range put out by governmental entities for protein is 10 to 35% of your daily calories, so even when we're talking about higher protein diets, they often fit within the recommended ANDR. Even though it's viewed as extreme sometimes, you hope high protein diet, it's really in line with some of the formal recommendations. Just if you're only using the RDA of 0.8 grams per kilogram, I do think you're kind of doing a disservice to some of the individuals you're working with.
Dr. Pastore: Yeah, I'm glad we completely agree on that point, and one of the things I'm seeing too, Dr. Tinsley, that I find concerning, is there's kind of like this cult wave of people that are ... They're kind of creating an amalgam of two different nutritional disciplines. I'm seeing people that are being quasi-ketogenic, that are also following intermittent fasting, and by combining the two, they have to consume a reduced quantity of protein to really fit within the definition of ketogenic diet, which is not the Atkins diet. It's not just a low carbohydrate, high protein diet. That's not ketogenic.
There's gluconeogenic amino acids and there's amino acids that are going to become glucose, so there's actually controlling of protein in the ketogenic population, so I'm concerned about that amalgam not being recommended by someone with knowledge or understanding, so that I have a fear there. And then I'm also concerned with, and I'm so glad you controlled for that in your trial, I'm seeing a wave of people doing that, the ketogenic and combining it with intermittent fasting, and then adding in one more phase, which is intense training, either aerobic or strength during a fasting state. You know, again, the way I was trained, we had the bullseye on the board and we knew the time frame and when was the most ideal to feed your athletes, and forgive me, but yes, having the graduate education was fantastic, but when you're practicing on some of the best baseball players and football players and hockey players that are making many millions of dollars to do well in their respective sports, that was ... You couldn't recommend, there's no way I would even touch that with a 10 foot pole.
Dr. Pastore: I mean, it's just so out there in left field. It just seems like it's not based on true scientific evidence to mix those three things together.
Dr. Tinsley: Yeah, no. I agree, and like you just alluded to, and I fully endorse this, that it's different when you're talking about elite athletes. Your margin for error is much smaller. A recommendation that might be okay, like maybe your generally active, otherwise healthy individual could get away with something like this, even if it's suboptimal, if they want to, but if you're dealing with elite athletes, their livelihood, yeah. That's a different situation. I love something a friend, Dr. Shawn Arent at Rutgers University says, and he really emphasizes the point that nutrition for physique and nutrition for performance are not the same thing.
There is some overlapping, you see the physique of professional athletes and you're like, “Oh yeah, I'm just gonna train for physique, I have to go low carb so I can be really lean like they are,” but you don't think about the amount they're training. About the actual performance they need to maintain. So if you're an athlete, performance has to come first. That likely should make you skeptical of some things, even like intermittent fasting or keto for a lot of sports. It should make you more skeptical of all those things.
Now, if you're general active individual and you're like, “I really just want a good physique. I wanna perform okay, I wanna be healthy, but I really just want a better body comp,” you have a lot more leeway. You can restrict calorie intake through intermittent fasting, through low carb, through low fat, you have a lot more flexibility, but I totally agree. And you have so much great experience working with these professional, truly elite athletes, and they're just a different breed than the general active population.
Dr. Pastore: It's a different, I think there's some black magic involved in what they can do, but ... When you meet baseball players that are so, they perform so well in the postseason. One of my most fascinating anecdotes that I've heard from that is that they can see the seems on the ball that's coming at them, and then you look at the relief pitcher the night before and you clock speeds of 94, 96 miles an hour. Yeah. Unfathomable. As someone who just got his glasses recently, I couldn't even a million years. And also I know how our friendship will continue for life. Thanks for the shout out to one of my alma maters, Rutgers.
Dr. Tinsley: Yeah, that's right. You're Rutgers, as well, yes.
Dr. Pastore: Great, great, great program. Scarlet forever. I do wanna segue to something really recent and modern if you don't mind, and going back to a great journal, that American Journal of Clinical Nutrition, this month there was a study examining a form of intermittent fasting and controlled calorie restriction, but now I'm more excited about your paper coming out, because it was a full year. This was 50 weeks, so this paper, there's a conclusion by the authors that intermittent fasting type diet might be equal to a calorie restricted diet for weight reduction and the prevention of certain metabolic diseases. Of course, this was not a study performed on athletes and strength training individuals, where your expertise, excellent expertise I would like to add, lies.
I was wondering if you had any comment on this study? If you had any thoughts on this paper? If you had a chance to read it? If you don't mind, my friend.
Dr. Tinsley: Yeah, so I was able to briefly review this, and honestly, I really agree with their big picture conclusion. Just to reiterate, and you just stated this very well, they essentially said that intermittent fasting was a viable alternative to normal calorie restriction, but not inherently superior, and I completely agree with that. And it's funny, I'll be at conferences and things and people come up to me and be like, “Oh, you're an intermittent fasting guy. Have you eaten today?” And this and that, and all that, and I kind of scratch my head. I'm like, “I research this, because I think it's interesting and there was no research in this area, so I wanted to put something out there,” but I have no vested interest in intermittent fasting being the best diet out there.
This really represents my position. This is a viable alternative, but not inherently superior. Now, there are some really interesting rodent data and preliminary human data showing possible physiological benefits outside of, say, body composition for intermittent fasting, but definitely can't be said at this point that it's physiologically superior. However, and with your extensive clinical experience, I hope you'll, imagine you would echo this, but an enormous part, probably a bigger factor to consider in any nutrition program is the actual ability of someone to adhere to it.
So, besides true food allergies and intolerances, something like that, I would argue this might be the biggest factor, so to me, if you have two alternatives and these are both roughly equivalent, say for body composition, weight loss, and things like that, then you get into the really critical factor of could you adhere to this? And just to use my own participants as an example, there's often a one to two week period, if we take someone for example who previously consumed breakfast and kind of ate throughout their whole day and went to bed, there's often a one to two week period where they're kind of adjusting to the intermittent fasting and they're like, “I don't know how I feel about this, but I'm hungry when I wake up,” all this, and after a short period of time they adjust to it, and then if they're seeing good body comp changes, by the end of the study they're like, “I'm just gonna continue this for life. I love this.”
But then we have other individuals who, they start out and they're like, “Yeah, maybe this is okay,” and by the end of the study, they're just like, “I hate this. Dr. Tinsley, as soon as the study's over, I'm never doing intermittent fasting again." I mean, that's really valuable information at the individual level, and this is something I've heard you say on other podcasts, just emphasizing the importance of individualizing aspects of nutrition, and I view the meal timing thing and intermittent fasting thing as something in that category. If it works for you, it helps you move towards your health goals, then do it. Go for it. And if not, if you're miserable, you're hungry, you're angry, you don't enjoy your life while you're doing it, then don't do it, because there are other viable alternatives.
Dr. Pastore: And I think your research shows that it could be just a great tool. I love your research and I have zero opinions, either. I think if someone can actually do it, what a fantastic thing to have. A new weapon in their arsenal, where they're not so sick of counting calories and monitoring everything they're consuming, and have an easier pathway, albeit easier for that individual. I think it is a fantastic thing, so I love what you're doing and I pray that you please continue. I can tell with your passion, I'm sure you're gonna keep publishing these great studies and so excited about the new one, my friend. That's gonna be amazing.
But yes, you and I are so in sync. We're so on the same page there. By the way, someone coming up to you at a conference asking you if you ate today, I have Celiac disease and I make it very well known I have Celiac disease. If I had a nickel for every time a fellow researcher came up to me and said, “Hey, how much do you miss pasta?” You and I would be having this conversation at the Taj Mahal or something. It just, it never ... The bad jokes just don't get old on these subjects, my friend. Wherever we put, wherever we hang our research hat or own a disease.
But yeah, I think my closing note on this topic is if there's a tool that individuals can use to improve body composition and mitigate disease, how wonderful that is to have variety, and that's what I love that you're showing is you were the first scientist to actually break this myth that you can be ... you can't be fit and practice this form of dnutrition, and I love what you did there, because the data sets are really remarkable. You know, we didn't even talk about the potential reduction in different disease states. The reduction in certain cases or normalization of lipid profiles, and look, I get it, if someone is normotensive, they're not hypertensive, if someone has a normal lipid profile, you're really not going to see that, a major change. But if someone has astronomically high triglycerides and they start practicing TRF under the guidance of a knowledgeable practitioner, they could potentially experience what we're seeing in the clinical literature. A dramatic reduction in those. And according to the literature, says they might experience a reduction in the cardiovascular event.
That, to me, is a miracle, and that actually means you're betting on the farm and not pharma.
Dr. Tinsley: Oh, I like that. I like that.
Dr. Pastore: If you don't mind me throwing out that little.
Dr. Tinsley: No, that's great.
Dr. Pastore: That little wonderful pearl.
Dr. Tinsley: Yes. No, it's great, and I appreciate all those kind words, and just ... Yeah, two notes on that, just to again give a huge shout out to my collaborator, Antonio Paoli, who has been along with this ring with me and we're working on current projects and will continue to. And other, just wanted to mention for the women listening, you may have noticed these few studies we highlighted that we've done previously are in males, and a big gap in literature had been looking at TRF, time restricted feeding in active females, and we actually just finished our data collection analysis on a big time restricted feeding study in active females, really similar to the study that was published in the Journal of Translational Medicine.
It was conducted here at Texas Tech University, and we should be submitting that for publication within the next month or so, so I know a lot of women will ask me, like, “Oh, you know, you see all these results, but do you think this would differ for me?” And up to this point, haven't been able to fully answer that question. I can give a best guess, but now we have data on that that will be coming out soon.
Dr. Pastore: That's awesome.
Dr. Tinsley: I think it will be really interesting. Maybe when it's out, we can chat again about it and ... Yeah, hash out that one.
Dr. Pastore: Everyone, if you're listening, Dr. Tinsley, he can crunch out and churn out papers like nobody's business. This man is a wizard. Dr. Tinsley, you are such a dear friend. I can't thank you enough for your generosity. I love our conversations always, and I so look forward to having another conversation with you again, my friend.
Dr. Tinsley: Absolutely, Dr. Pastore. Thank you very much for your time and it was a great time chatting with you as always.