What New Science Says About Building Muscle | Brad Currier

Muscle is having a moment, and for good reason. As functional medicine clinicians, we recognize that muscle isn’t just about strength or athletic performance. It’s central to metabolic health, resilience, mobility, healthy aging, and longevity. Yet resistance training can still feel intimidating for many of our patients, and even for some of us.

That’s one of the reasons I was so excited to sit down with Brad Currier, PhD. Brad was part of the team behind the first major update to the American College of Sports Medicine resistance training guidelines since 2009, and he has a remarkable ability to translate exercise science into practical, evidence-based strategies that clinicians can use immediately. In partnership with Timeline, we also explore the emerging science of Urolithin A and mitochondrial health, including exciting research on muscle function, recovery, and performance across sedentary adults, older individuals, and elite athletes.

This is an approachable, practical conversation that I think will change how many of us think about prescribing, and supporting, movement as medicine. ~DrKF

Resistance training is one of the most effective interventions for preserving muscle function, supporting metabolic health, and promoting healthy aging, yet many patients remain overwhelmed by conflicting advice about how to get started. In this episode of New Frontiers, exercise physiologist Brad Currier, PhD, discusses the first major update to the American College of Sports Medicine resistance training guidelines since 2009 and what those changes mean for clinical practice. He explains why adherence should be the primary goal, how home-based and lower-load training can deliver meaningful results, and the evidence behind protein and creatine recommendations for muscle health.

In partnership with Timeline, the discussion also examines the cellular foundations of muscle health and longevity, including the role of mitochondrial quality control and mitophagy. Brad reviews the emerging clinical research on Urolithin A and its potential to support mitochondrial function, exercise adaptation, recovery, and physical performance across diverse populations.

In this episode of New Frontiers, learn about:

Dr. Kara Fitzgerald: Hi, everybody. Welcome to New Frontiers in Functional Medicine, where we are interviewing the best minds in functional medicine. And of course, today is no exception. I am here with the always brilliant, always fun-to-talk-to Dr. Brad Currier. He is a PhD exercise physiologist who comes from the laboratory of Stu Phillips, who you might follow on Instagram, like I do. They’re just pumping out some of the best science, no pun intended, in resistance training, performance, and healthy aging.

Dr. Kara Fitzgerald: He’s been really involved, along with a number of luminaries in the exercise physiology space, in updating the American College of Sports Medicine resistance training guidelines. This is the first major update since 2009. The conversation today is a dive into that through a clinician lens. How do we think about the exercise prescription that we are providing our patients? How do we support that for different indications, etc.? So from the couch potato to the elite athlete, we really cover the gamut. And then one of the things we get into after that is how we support muscle health more broadly. As a clinician, as somebody interested in your own health, supporting your patients, your family, and yourself, it’s very practical.

Dr. Kara Fitzgerald: You will learn a lot of information that you’ll find useful, both in your delivery of care and perhaps for yourself. Again, a fun conversation. This is in partnership with Timeline. We’ll dive into mitochondrial health and some of the extraordinary science that they’re up to over there. We did a nice tour of the literature in athletes and also the literature in couch potatoes and older adults using Urolithin A as well, so stay tuned.

Dr. Kara Fitzgerald: It is always awesome to be able to pick your brain and I know that my audience loves it. We did a great webinar together, and it’s great to have you on the podcast. We’ll be able to reach many, many more people. I want to talk about your involvement with a whole bunch of rock star scientists in redefining the American College of Sports Medicine position statement. It’s a big deal what you guys took on and what you did, and I want to unpack it. So give me the history of the exercise prescription through this lens, why you took it on, and then we’ll unpack what it is, why it’s important, and why we need to know as clinicians.

Brad Currier, PhD: Absolutely. And thanks, as always. It is a treat to be here and to be able to pick your brain too, and just have a great dialogue, as always. The American College of Sports Medicine is the largest sports medicine organization in the world. It includes exercise scientists, personal trainers, academics in this space, and members in over 90 countries. It’s a massive organization. Organizations like this, when they’re a governing body or leading voice, will have position stands. This is when an organization says, “Here’s our perspective on this topic based on all of the research that’s out there.” An exercise prescription would obviously be right front of mind for exercise science and sports medicine.

Brad Currier, PhD: Over the last several decades, the American College of Sports Medicine has put out position stands on numerous topics. The position stand on resistance training prescription was last updated in 2009. Our team’s recent update came just over 17 years later. The reason we took it on was twofold. First, we wanted to update the position stand. A position stand is a tool in a clinician’s toolbox. Clinicians are seeing patients and clients all day. You don’t have time to read the tens of thousands of papers that are published on any given topic. A position stand should be a systematic summary of where the evidence stands so it that can be part of the information clinicians have to inform their practices.

Brad Currier, PhD: So it’s important to update with the research and the duration between position stands was reason enough. But we really wanted to expand and develop the position stands that were existing on resistance training prescription by incorporating the systematic methodology used in evidence-based medicine, but also tailor the position stand to the average person. Because in some cases, a lot of the work that’s out there focuses on the elite of the elite. How do we take these high-level athletes and train them? That’s super cool and very relevant, but for 99% of us, it’s not applicable. We really wanted to update the position stand and make sure it was applicable to both the elite and the masses.

Dr. Kara Fitzgerald: That’s awesome. That’s huge. So the 2009 position statement was really designed for the 0.01% in their recommendation?

Brad Currier, PhD: It is probably one of the most cited papers in exercise science history. It really is a commendable work in itself. There’s a lot of great stuff in the 2009 stand. Some of the critiques were that it was maybe less applicable to the majority of people. It’s important to remember and have context for this. Sixty percent of Americans do no resistance training, so more than half of the people we see are not just failing to meet the guidelines—they’re doing nothing. And so when we talk about prescribing resistance exercise to these individuals, it’s going to have to look a little bit different than it does for advanced trainers.

Dr. Kara Fitzgerald: Right. I always think in terms of cycling because that’s my place. We’re talking about shaving off a second, or even less than that. So for the elite of the elite, it’s cool if you’re into athletics and you’re into looking through that lens. But as you say, it needs to be for everybody. What a cool awareness for you guys. When did you hatch the idea to take on redoing this, and who was part of your team?

Brad Currier, PhD: Yeah. It was an amazing team across the board. I think total there were 13 or 14 co-authors on this. Besides myself, the corresponding author was Stuart Phillips, “Mackinprof” on socials, as people may have seen him. He was my PhD supervisor and that’s when this project started.

Brad Currier, PhD: It honestly came about conveniently during COVID. A lot of the work our lab does is working with stable isotopes, muscle biopsies, and running these clinical trials. But for the period of time when we weren’t able to run these studies, particularly in older adults, something I really turned my attention to was medical statistics. I felt it was an area that would be a good advantage to have when we got back into doing clinical research. Through that, there was a series of publications that we ended up producing all around this idea of exercise prescription and what is the most effective way to prescribe exercise for muscle strength, physical function, and muscle building, really applying these statistical methods to that problem.

Brad Currier, PhD: The byproduct of that was the opportunity to update the American College of Sports Medicine Position Stand. This was really an extension of some work we had been doing during that time. Obviously, we got back in the lab but continued this in parallel next to the lab work.

Dr. Kara Fitzgerald: Talk to me about what it is. What kind of the foundational recommendations need to be happening? Maybe with a little bit of an eye toward how we’re going to be bringing this forward to our patients.

Brad Currier, PhD: Absolutely. If there is one thing I can tell clinicians to take from this, it is that anything is better than nothing.

Dr. Kara Fitzgerald: Right. I love that.

Brad Currier, PhD: It’s not sexy, and that’s okay. But it’s really isn’t. If we break it down a little bit, like I said, most people do none of this. We see the biggest benefit when folks go from doing zero exercise to any exercise. Of course, we’re talking about massive improvements in strength, muscle quality, our physical function, like being able to get up out of a chair. These things all improve with resistance exercise.

Brad Currier, PhD: What’s really key about this is that for so many people, the objective should not be, “What’s the perfect prescription to maximize X outcome?” It should be, “What’s the perfect prescription to make this person come back and do it again?” Because this needs to be done consistently. That was really the big reframe in messaging, where for so many people, adherence should be the main objective for the first few months.

Brad Currier, PhD: Really, what I hope this paper does is liberate both clinicians and individuals, where for the first time, we have this massive body of evidence—It’s over 30,000 people included in this review and it’s a systematic method where someone could take our methods, do it themselves, and theoretically come to the same conclusions. It’s a reproducible way to synthesize this evidence.

Brad Currier, PhD: With that, we now have this massive body of evidence showing that traditional resistance training works, but it doesn’t have to be just that. Working out with resistance bands, training at home, and training with lower frequencies than people probably expect is so beneficial to the vast majority of people who are currently doing nothing. That’s the biggest thing. We need to get people doing something.

Brad Currier, PhD: Of course, there are results that are applicable to those individuals who are well-trained, who are trying to get that little bit out of their muscle strength, or power, or whatever they’re looking for. But the biggest takeaway is that anything is better than nothing. We need to get more people doing resistance exercise regularly.

Dr. Kara Fitzgerald: By the way, folks, we will link to the Position Stand in the show notes and any additional information that might be useful for us in this arena and thinking about the exercise prescription.

Dr. Kara Fitzgerald:  I guess I have two thoughts. I’m envisioning someone at home with a couple of cans, wondering what they can use, and just starting there, just doing whatever. You know, there’s a couch, you can do some squats while holding onto the back of the couch, whatever you need to do. So, I’m curious about your thoughts on having a home-baked protocol. And actually, even before we get into this home-baked protocol, I also want to thank you guys. Thank you. I follow Stu Phillips on Instagram, and we’ll link to him and maybe some of the others.

Dr. Kara Fitzgerald: One of the things I really like about him is that he’s very down to earth. Because muscles are having a moment in the sun right now—protein and muscles—and you get some people who are so hyper-buff and doing such outrageous stuff, and I think it’s probably off-putting for the rest of us. You know, I’m never going to have 3% body fat. That’s just not in my future. So I like that you and Stu Phillips and some other people are just bringing the branch down for the rest of us, so thank you.

Dr. Kara Fitzgerald: So let’s talk about somebody starting with a home protocol.

Brad Currier, PhD: Well, you’re very kind. But yeah, Stu, of course, I was very lucky to be trained by him. He’s very humble, and he wouldn’t tell you, but he is truly a legend in the field. He’s the most cited in sports science and muscle place for a reason. But the whole team, Abbie Smith-Ryan, Eric Rawson, Brad Schoenfeld—it was a treat for me. These are people who I’ve grown up and developed, reading their papers. To be able to collaborate on this, as well as many other researchers who are budding superstars. I highly recommend following that whole author list and their work.

Dr. Kara Fitzgerald: Cool. It’s fun, and like I said, it’s not intimidating. It’s really down to earth. So we’ve got somebody starting with a home protocol and maybe we can talk about that. When we were talking off-air, you mentioned that what we’re prescribing to “every man” who hasn’t gotten off the couch in a long time is really not necessarily that different in structure than the elite athletes. So for those of you who are highly trained or who are working with people that are super elite, you can take this home. So I want you to think about that. And then I’m just going to sprinkle in another thought around how we get people to continue.

Dr. Kara Fitzgerald: I keep exercising because I feel good after. I get clarity of thinking, and over time my physical feels better. Anyways, talk about what I’ve just thrown out there and wherever you want to take it.

Brad Currier, PhD: Absolutely. There are three key principles that we highlight in this paper, and I would say these three are applicable to a first-time exerciser or an eight-time Olympian. The whole spectrum. The three key principles are progressive overload, individualization, and specificity and I’ll just say a quick word on each of those.

Brad Currier, PhD: Progressive overload is the idea that for our body to continue to adapt and improve, we need to increase the stress we’re putting on it. So in the case of a first-time exerciser, that might be two or three wall push-ups. In the case of an elite performer, if we’re in the off-season of an NHL player and they’re trying to get stronger, we need to increase the amount of load they’re lifting for them to increase their strength. So progressive overload is applicable across the spectrum, but it’s going to look very different depending on the person.

Brad Currier, PhD: The same is true for individualization. Individualization is how we tailor a program to an individual’s needs. For the first-time exerciser, that could be they can’t afford a gym membership or they don’t have equipment at home. We can look at, are there some things in your house? Are the $30 elastic bands that you can exercise with on Amazon? Is that in the cards for you? Maybe, with their work schedule, they can only exercise for fifteen minutes each morning, or twice a week. How do we tailor this program to that individual’s needs? And of course, that’s applicable the high-level performer as well, with their individual needs.

Brad Currier, PhD: The last is specificity and this is just the idea that you’ll adapt in line with what you practice. So, if you want to get stronger, you need to be challenging your body with more weight than you’re used to lifting. That might may take the form of an elastic band, or it may be three, four, or five plates on a barbell. But if we’re going to get good at something, we need to have our training be specific to our ultimate goal.

Brad Currier, PhD: So, those are the three principles that I would say are applicable across the spectrum. And I know I covered a little bit of the home-based exercise, or program there, but that’s really what I would say would be the focus if we want to apply this to a wide range of populations.

Dr. Kara Fitzgerald: The other Brad, Brad Schoenfeld, published on his Instagram—I don’t know that we’ve necessarily linked to Instagrams on our show notes, but we could do it because he’s another fun one to follow—And he just busted a bunch of myths around what we’re supposed to do. And I think one of them is that you could actually go for more reps of a lighter weight and achieve the same outcome, as opposed to jacking up and jacking up. Which I have to say, I’m more of a fan of that. Can you just speak to that? That’s less intimidating to me than, like, you know, a ton of weight.

Brad Currier, PhD: Absolutely. And this is something that actually, from some of the earlier position stands, was thought to be true at the time. It’s what’s called the strength-hypertrophy-endurance continuum. It was this idea that if we’re lifting a weight that we can only really lift two, three, four times, that’s where we’re going to maximize strength. If we wanted to maximize hypertrophy and muscle growth, we needed to be in that middle six to twelve rep range. And anything more than that, over twenty reps, is just muscular endurance.

Brad Currier, PhD: This is something now that Stu’s group was a huge, huge part of, but many others around the world have replicated it. We’re showing that what really drives muscle growth is the work completed, and we can think about that as the effort that we’re training with.

Brad Currier, PhD: In these randomized trials, what they did is they would have multiple groups. Some people training with heavy weights, some people training with light weights, and they would put them through this training program of, depending on the study, eight, twelve, or sixteen weeks. What they saw is that when individuals were lifting to failure, and now we actually know it’s just close to failure, so getting near the end of their maximum possible repetitions, the amount of muscle people built over those several months was the same. There was no difference.

Dr. Kara Fitzgerald: Awesome.

Brad Currier, PhD: And I think you’re right on the money where this is a great example of how knowing more and having more data, we can understand that if someone needs to improve their muscle health, if they want to build a little bit of muscle in this case, they don’t need to get under that massive barbell. There are many ways to accomplish this goal, and that really helps feed into the individualization of if we want someone to do this program regularly, let’s make sure it’s well suited to them. And if someone doesn’t like big weights, that’s okay. We can accomplish a lot of this without using big weights. So that’s a great point. And yeah, Brad had a great post on that, showing how it kind of breaks down and how it’s evolved.

Dr. Kara Fitzgerald: All right. Just down this rabbit hole a little further. Do we want to be lifting free weights? I mean, what about the weight machine debate? Why don’t you settle that? What do you guys think?

Brad Currier, PhD: Yeah. So that was actually something we looked at in this position stand, and others have as well. The short answer is that it doesn’t matter. The two nuances I would highlight to this are, it doesn’t matter for almost all of us. Because when we think back to that example, or just this situation where more than half the people in our society do nothing, when they go to doing something, whether that’s on a free weight or a machine, that’s not going to be the difference. There’s going to be so much benefit from just doing something.

Brad Currier, PhD: Where free weights might have a bit of an advantage, actually,  is part of that principle of specificity. Once someone is very well trained, if they’re, say, an Olympic lifter and they need to get really good and lift as much weight as they can with these select movements, that individual will be better off training with those specific movements.

Brad Currier, PhD: So for most of us, you can train only on machines for months and months and months and you’re not going to hit a plateau. The variety is nice. Some people like certain exercises on machines versus free weights. But the biggest bang for your buck isn’t machine or free weight. It’s doing either.

Dr. Kara Fitzgerald: Yeah. That’s right. That’s awesome. I use a mix. I don’t like kettlebells but I’ll do them because you can get a lot of work out in a short amount of time. But my trainer would bring up the fact that you’re getting that neuromuscular development. You’re working on balance and grip strength. So there are some other side benefits, or maybe tangential benefits from actually using weights versus machines. But if I’m feeling tired and it’s all I can do to actually get myself to the gym, machines, people, you know.

Brad Currier, PhD: I totally agree. Doing the machine is going to be better than doing nothing. And you bring up a great point, which I would highlight for any clinician, who themselves, or who have patients that want to incorporate more exercise into their routine. Certainly, if you feel equipped and have gone through the education of what this looks like in an exercise program, great. If not, there’s an increasing number of certified personal trainers, kinesiologists, and exercise scientists who are usually located within a lot of these medical centers or just in the community that can be a great resource and are more than happy to partner up.

Brad Currier, PhD: So it’s really something that’s important to add to people’s lives and something that you might see when you’re programming for individuals’ specific needs is exactly what you mentioned there with grip strength using the kettlebell. These compound movements, or exercises where we get multiple benefits, are some of the best bang for our buck. Because time is the most frequently cited reason people don’t exercise. Maybe we talked about it a little offline, but in my mind, there’s an element of lack of prioritization in some cases. It only takes five or ten minutes to get most of this benefit. If we realize the value, we can find a way to work that in. But time, there are a lot of things pulling people in different directions. Work, kids, family, social life, being human, being sick.

Brad Currier, PhD: When we have ways that we can really get the most effective exercise for shorter periods of time, like an exercise where we’re exercising both our grip strength, our hamstrings, our core. When we can get that all into one, it can be a huge time saver.

Dr. Kara Fitzgerald: Yeah. I’ll do a kettlebell superset and I’m just muttering swears under my breath. But, you know, I’ve gotten a good workout. I don’t love it, but…

Brad Currier, PhD: I haven’t had a kettlebell that’s talked back to me yet, so just keep giving it to the kettlebell.

Dr. Kara Fitzgerald: All right. I’ve got a bunch of questions, so I’m going to circle back to protein. I know people are thinking about protein, and you guys dispelled some myths in that arena as well. But first, form. So you touched on the idea of training and we need to be mindful. When I’m prescribing—well, actually, you know how I start with my patients? For people who come to me who are completely sedentary and maybe exercise resistant, my first question to them is, “What would you be willing to do?” Let’s dialogue on it. Let’s come up with a list. I won’t even send them home that day with an exercise prescription because they’re going to feel pressure. They don’t want to do it. But just begin to ponder what you might consider doing. Then we’ll dialogue, and kind of take it from there and build on it over time.

Dr. Kara Fitzgerald: But when it comes to prescribing an actual resistance training protocol, I would not pretend to have that ability. I would want to refer. Well, I don’t want to refer—I refer all of the time. And of course we’re in functional medicine, so we’re working with individuals who come to us with a condition. I see many, many of my patients, mostly women but some men, have a bone loss disorder of some form and I refer for resistance training all the time. But again, it has to be careful.

Dr. Kara Fitzgerald: It was interesting, I just talked to a patient yesterday who went to PT to get some training. She has osteoporosis, so that was her prescription. She was very good about it and she ended up going to a place that I wasn’t familiar with, but I supported her. There was insurance coverage. She ended up getting injured, so whoever was training her wasn’t fully versed in it, which stinks because it sets us back a little bit. This individual was outside of their league.

Dr. Kara Fitzgerald: So how do we know? I’m referring for appropriate guidance, for lifting, for a good protocol for somebody with osteoporosis or cardiovascular disease or whatever? When we’re thinking about these conditions, where are we sending our patients?

Brad Currier, PhD: Yeah. So in that case, obviously it will vary so much around the country, where you are, or around the world, where you’re located, and what kind of facilities there are nearby. I would look for some of the accredited personal trainers in a case like that. You can actually have specialties in working with these populations that may be living with a condition such as osteoporosis. Of course, they’re well versed in working in close collaboration with that individual’s medical team and healthcare providers so that it is suited to that individual.

Brad Currier, PhD: Because you’re absolutely right. There are considerations that need to be made, particularly for individuals in that scenario. I think something to consider, not just for individuals with a condition like osteoporosis, but as a whole for someone who’s new to exercise, is that it’s a brand-new world. Resistance training does have the myth of being dangerous. It’s scary, and that’s understandable. It’s not as comprehensible as saying, “I have shoes, I’ll put them on and go for a run.” Right? There’s all this equipment and so much noise about how to do it right. So there is a fear that’s a real barrier for a lot of people. I will just point out as a note that the injury rate is actually the same, if not lower, in populations for resistance training versus aerobic training. But I digress.

Dr. Kara Fitzgerald: Yeah, that’s important. That’s important because I think you’re right.

Brad Currier, PhD: There is actually a bit in the position stand where we talk about the injury data. Certainly, one adverse event, whether it be muscle soreness, injuries, or serious adverse events, depending on which one we’re talking about, it’s no different across the board. But doing it properly is important. So, back to what we were saying, something I think is critical for people working with folks who have a condition such as osteoporosis, but also first-time exercisers, is not starting too quick. That is where we get into so much trouble. It’s very important that we work with the individual. My first questions are always, “What’s your goal?” Why are we doing this? I find that helpful to draw back on when you’re actually coaching them.

Brad Currier, PhD: What’s the goal? What are we working with? What equipment or facilities do we have available to this person? What are your no-fly zones? Are there exercises or things that you absolutely do not want to do? Because that’s a pretty quick way to make sure they never come back. So, within those confines, having an idea of the major movements that are going to be good for them and teaching them that. The first couple of months is just an education of, all right, I think getting into something like the kettlebell swings you’re talking about is good, but let’s make sure you know how to do a proper hip hinge. Do we know how to activate our core muscles to stabilize?

Brad Currier, PhD: Already, this movement, albeit maybe body weight without resistance, is more than the person is doing, or is going to be a challenge for them. They’re not going to walk away feeling like they got zero from this session. But over time, you’ll progressively build that confidence and ability so that we can continue progressing this individual over time. So not starting too quickly is one of the biggest pieces of advice I would give across the board for this.

Dr. Kara Fitzgerald: I’m going to just have the team reach out to you later to get links to the accreditation organizations so clinicians can link and know who they need to refer to.

Brad Currier, PhD: Yes, absolutely.

Dr. Kara Fitzgerald: Another cool sidebar of having a trainer—I speak from experience, but definitely from referring many, many patients to trainers—is that you have a commitment. You’ve got it baked in. Trainers don’t like it if you stand them up or if you’re really late, by the way.

Brad Currier, PhD: Being accountable to someone else is a little bit more motivating. It’s just human instinct when someone’s there.

Dr. Kara Fitzgerald: It is. And then, again, just speaking from my own experience, I might stay longer and do a little bit more than I might otherwise do. Because I do it. For my adulthood, I’ve been engaged in resistance training. Actually, let me tell you my background. The reason I have been consistent with resistance training is because I have pretty significant scoliosis and I wore a brace as a kid. The doctors were smart and they had the foresight to say, “Look, if you’re exercising,” and they gave me a whole suite of exercises, “you can take your brace off.”

Dr. Kara Fitzgerald: I hated wearing my brace, so I did all of the exercises they wanted, and my mom got me to do them. And then I would be out and physically active because I could take my brace off. Many years later, flash forward to medical school, a friend of mine was also diagnosed with scoliosis and braced as a kid as well. She struggled with really profound back pain, and I didn’t. And I am certain it’s because my core has been trained. Not only my core, but also the habits and this experience as a kid. So just kind of hitting it home.

Brad Currier, PhD: Yeah, that’s a great story. I didn’t realize that. But you’re absolutely right. It is an indispensable tool for function and health throughout the lifespan, in my view.

Dr. Kara Fitzgerald: Yeah. I’m grateful I developed that habit and it’s still with me, even if I mutter under my breath sometimes, because I get how important it is.  I mean, if I don’t stick with a decent protocol, I will experience back pain after a period of time. Because my core really stabilizes my spine.

Dr. Kara Fitzgerald: Yeah, I’m grateful that I developed that habit and it’s still with me. Even if I’m muttering under my breath sometimes because I get it. I get how important it is. I mean, if I don’t stick with a decent protocol, I will experience back pain after a period of time. I can feel it because my core really stabilizes my spine.

Brad Currier, PhD: I’m with you too. For my ailments, I was a golfer in college. That’s what brought me down to the States originally and same, when I don’t exercise, the body starts falling apart. I know the data is strong and the cognitive benefits, like you mentioned earlier, that’s something I’ve actually only really noticed more in the last year or so. But there is a calmness to the mind and an alertness that I notice on the days that I exercise. So it’s pretty remarkable.

Brad Currier, PhD: One thing—I know we’ve got lots we want to cover—

Dr. Kara Fitzgerald: We have a lot to cover, but tell me.

Brad Currier, PhD: On the exercise, I was just going to say groups are amazing for people getting into it. The social element is huge. So it doesn’t need to be a one-on-one trainer. Exercise groups are fantastic.

Dr. Kara Fitzgerald: That’s right. That’s how I did my private training. I did a small group, and it was super motivating and it was a lot of fun. One other injury story was cycling. So I became a really avid cyclist when I was in my early twenties, and I continue to be. But I ended up developing chondromalacia patella because I was just pushing the big ring all the time and my muscles weren’t balanced. And it was an orthopedic doc who prescribed lifting, taking care of my hamstrings and my quads. And that really changed my game as well. So it was an injury that brought that more intentional resistance training. So I had my back exercises and then expanded to that. That was back in my twenties, and I’ve been consistently doing that as well to save my knees.

Brad Currier, PhD: Amazing. Yeah, it’s a gift that keeps on giving.

Dr. Kara Fitzgerald: So I want to move into how we actually support our muscles growing. We’ll talk about the incredible research on Urolithin A, and then we’re going to talk a little bit about your stack. But I just wanted to chat around protein as well, and one of the myths you guys have busted. This is the idea that we really need to be consuming, like, swallowing down massive amounts of protein immediately after we resistance train. I think that overwhelms people as well. So speak about using protein in the context of building muscle.

Brad Currier, PhD: Yeah, absolutely. Some of the names we mentioned earlier, Stu Phillips and Luc van Loon, these are people who have really been leaders in this space for decades, looking at these protein requirements. There’s a whole great wave of researchers now. Protein, unlike carbs and fats, is not a fuel. It’s a building block. We need it for structure. In the context of resistance training and building muscle, protein is the icing on the cake. Lifting is the actual cake. I credit Stu for that one. It’s a great analogy.

Brad Currier, PhD: When it comes to protein timing, this anabolic window was something people thought for a while was going to be important. What researchers did was look at muscle protein synthesis.This is a measure where we can use stable isotopes, which are kind of like little flags on amino acids, or we can measure the amino acids in something and we would measure how quickly these amino acids would get built into muscle protein. You can look at how that rate of muscle protein synthesis changes after different types of exercise and different types of nutrition.

Brad Currier, PhD: Really what we’ve seen is that the anabolic window, when muscle is extra sensitive to protein following exercise, is not nearly as small as we thought it might be. If people could take one piece of advice on protein, if the total amount of protein you’re eating in a single day is sufficient, you’ve got your bases covered. Timing protein, distributing your protein, all of that is much less important than going to the gym and eating enough protein over the course of an entire day.

Brad Currier, PhD: How much should you be eating? Maybe you can help me with the conversion to pounds, but the RDA is 0.8 grams per kilogram of body weight. That’s not enough for a lot of people. It’s enough to avoid deficiency. It’s not enough to thrive. The current research would indicate that 1.2 to 1.6 grams of protein per kilogram of body weight each day is a great window. If you’re hitting that amount, then you’ve got your needs met.

Brad Currier, PhD: I would say that you don’t need to be fussing about the timing of it. If you can get enough through food, that’s fantastic. Supplements are a great option if you don’t have the appetite for more food. Protein is satiating. But the biggest thing on protein is that it’s not the big mover of muscle growth. Just getting enough each day is the biggest thing to make sure you’re checking that box.

Dr. Kara Fitzgerald: Do we need to have the full complement of amino acids? Do we need to do animal protein, or can you include some vegan proteins, vegetarian proteins?

Brad Currier, PhD: Yeah, great question. You absolutely can look at vegetarian and vegan sources. This is a space that’s really come a long way in the last twenty years. Rightfully so, there was a narrative that it has to be animal protein because it’s got all nine essential amino acids. We need them. Absolutely true. Those nine essential amino acids are essential for a reason. You need them and a lot of plant protein sources would not have all of those. They’d be missing some essential amino acids.

Brad Currier, PhD: Now, because so much of this plant-based, vegetarian, and vegan proteins have come such a long way, you can get enough protein from these sources. Oftentimes that might be through a blend. It’s something that’s fascinating that you can hear others talk at length about it, but evolutionarily we see people around the world figuring out they need to pair a bean and a lentil, or a lentil and a grain. Because together that actually provides a complete amino acid profile.

Brad Currier, PhD: So you can absolutely get enough through plant-based sources. It might take a little more judicious planning, but a lot of these supplements now are so, so good, especially when you get blends of vegetable protein sources. As long as that total protein content is in that 1.2 to 1.6 grams per kilo range, you’ll have your needs met.

Dr. Kara Fitzgerald: Awesome. And I know your lab, Stu Phillips’ lab, has researched this specific question and published on it, so that’s great to hear. And by the way, if you’re thinking collagen will do the trick, it doesn’t. I know that comes from the Phillips lab as well.

Brad Currier, PhD: I joke to people that it is quite literally used as a placebo in some of these trials because it does nothing for muscle.

Dr. Kara Fitzgerald: Wow. Isn’t that interesting? Fascinating. All right. So we’ve talked about the logistics of exercising and the update to the American College of Sports Medicine position statement that you worked on with your colleagues. We need to be exercising in any way possible. We can do it at home, we can go to the gym, etc., etc., etc. We just need to be engaging in movement and specifically in some resistance training.

Dr. Kara Fitzgerald: Now let’s talk about how we want to support optimal outcomes. And specifically, I want to talk about some of the ridiculously amazing science behind Urolithin A. You know, I’m a huge longtime fan. Basically as soon as you landed in the U.S., I found you and have been a fan, and a huge fan of the commitment to science. You guys have a lot of science on sedentary individuals, so you’ve really answered this question with regard to Urolithin A from sedentary individuals, full-tilt couch potatoes, on up to elite athletes using it. So what is it? Talk to me about what Urolithin A is and why we care about it in the context of muscle.

Brad Currier, PhD: Yeah. So Urolithin A is a natural molecule, and it was discovered by a group of scientists and physicians who ended up, of course, going on to found Timeline here. But they were working in Switzerland and trying to understand why superfoods have the health benefits that they do. Urolithin A actually came from looking at the pomegranate and really deconstructing the pomegranate.

Brad Currier, PhD: Urolithin A is a postbiotic, meaning that when we eat foods that have certain polyphenols, like pomegranate, nuts, and other berries, our gut microbiome should convert those polyphenols into these postbiotics with beneficial effects, the main one being Urolithin A. Its mechanism of action is focused on the mitochondria, where Urolithin A is the only clinically proven molecule that stimulates mitophagy, the recycling process that our body has to renew damaged mitochondria. So Urolithin A is a natural molecule. It rejuvenates mitochondria. After seeing this—Full credit to the team here, where they took it through that rigorous, almost pharmaceutical-like process of trying to figure out if it was beneficial.

Brad Currier, PhD: Timeline was founded over 15 years ago, and there are now ten-plus years of great research published in top journals like Nature Metabolism and Nature Medicine showing that Urolithin A was improving lifespan by 48% in these preclinical models. It was increasing muscle strength and endurance by 15–30%. There was a lot of promise, saying okay, we love our animals, but is this beneficial for humans? And over the last ten—

Dr. Kara Fitzgerald: Can I just say, before you talk about the human piece, I mean, I believe it outperformed rapamycin, right? It was right up there with caloric restriction.

Brad Currier, PhD: Yeah. Both were right around 50%. Rapamycin and caloric restriction were were about half, so 25% to 30% for a lot of those.

Dr. Kara Fitzgerald: It just puts the darling longevity molecules really to shame. The only one that was right with it, maybe slightly above, was caloric restriction in the preclinical models. Okay, go ahead. Transition over to humans.

Brad Currier, PhD: Yeah. We love the animals, but at the end of the day it’s about helping people. What the team did was really take this approach of first looking at the question: Is Urolithin A safe? Is it bioavailable? The answer was yes, across the board. It has a glowing safety profile.

Brad Currier, PhD: The next key question was: Do we need to supplement with this, or can we get it from food? I’m a big advocate that whenever you can get something from food, you should. So the team ran a study originally in the United States, but it’s now been done with hundreds of people all over the world, looking at how much Urolithin A they would naturally produce following a glass of pomegranate juice, which is rich in those precursors—the polyphenols—versus how much they’d get after taking one dose of MitoPure, a pure, FDA-approved version of Urolithin A.

Brad Currier, PhD: The short answer is that over 80% of people do not make it naturally. Even among the small number of people who can make it, they got six times more Urolithin A from the supplement than they did from dietary sources. So Urolithin A is really one of those unique situations where, through supplementation, we can unlock a power that’s in our food that we otherwise wouldn’t be able to experience these benefits.

Brad Currier, PhD: So we saw that you needed to take it as a supplement and that’s when all the double-blind, randomized, placebo-controlled trials started. You can steer me to whichever ones you want to talk about, but the first ones were really looking at what’s it really doing at the cellular level. Individuals would consume MitoPure daily, and taking muscle biopsies, looking at their blood work to see what’s really changing. Overwhelmingly, it was this mitochondrial health signature. In these muscle biopsies after one month, you see that upregulation of cellular energetics, these mitochondrial genes and pathways, actually in a dose-dependent manner of how much Urolithin A they took, up to one gram. Beyond one gram, there weren’t any added benefits. So 500mg to 1g is that sweet spot.

Brad Currier, PhD: And that was the dose that was used in longer trials, like you said, spanning from middle-aged older, overweight, Olympic athletes… Whatever it was, those are the doses that were used. And now the team just kicked off our 28th clinical trial looking at how Urolithin A can benefit so many different tissue types. But really, muscle was a focus because of its role in healthy aging, healthspan, and longevity. And those first few trials that focused on that were really incredible. They showed significant improvements in strength, around 12% clinically.

Dr. Kara Fitzgerald: In sedentary individuals.

Brad Currier, PhD: In sedentary people, yeah. That was a trial published in Cell Reports Medicine where these middle-aged individuals, 40 to 65 years old, below-average fitness, a little overweight, honestly representative of the population. They just took either 500mg or 1g daily for four months. Both groups showed 10–12% improvements in strength with no changes to their exercise or diet.

Dr. Kara Fitzgerald: That’s crazy.

Brad Currier, PhD: And you do see that improved mitochondrial signature in these individuals. It was a huge amount of work that the team did, extending this to then older individuals up to 90 years old. And now I’m working in athletes, looking at not only whether it can improve performance, in some cases. There was just a study done by an independent academic researcher, Dr. Mitchell Naughton, down in Australia, with really high-level academy soccer players showing that six weeks of supplementation was improving their vertical jump and their performance on fitness testing compared to placebo.

Dr. Kara Fitzgerald: I feel like I just want to take a second and say that when you improve something in an elite athlete, when you make a difference there, that’s where the rubber really meets the road. It’s easier, it’s kind of low-hanging fruit, to make changes in somebody who’s sedentary, who’s got some inflammation going on, etc. I mean, obviously what you guys showed is ridiculously impressive. I know that the VO₂ max was improved by 10%, which is like a decade, that’s about lowering the bioage of VO₂ capacity by a decade in sedentary individuals.That’s nuts. And also, by the way, CRP was shown to be lowered as well. But then when you go to elite athletes, that’s a whole other kettle of fish because they’re already peak. They’re already peak, so to make them more peak, it’s harder.

Brad Currier, PhD: Yeah.

Dr. Kara Fitzgerald: Because they’re already there. And so, with that, just having that context, what did you guys find?

Brad Currier, PhD: Yeah, in the athletes. So there’s actually been three studies done now. In that high-performing sense. In that soccer player study, was these younger individuals, right around early adulthood, they were the highest level of academy soccer players in Newcastle, Australia and they went through a six-week training camp. One group consumed one gram of MitoPure per day, the other got placebo. After the six weeks, and you know, training camps are a very intense period, the group taking MitoPure had significantly greater improvements in their vertical jump. There were a few outcomes, but one that I was really intrigued by was something called a Yo-Yo intermittent running test.

Brad Currier, PhD: Maybe people have done something like a beep test in high school where you’re running side to side in the gymnasium trying to beat the beep. It’s basically a measure of endurance and capacity—how long can you go in this test—that was significantly improved in these players as well. So not just muscle power and jumping, but their ability to sustain performance for extended periods of time.

Brad Currier, PhD: One of the other studies was a similar demographic. It was actually done in Australia as well by Professor Louise Burke’s group. Dr. Jamie Whitfield was the lead on that. Louise Burke is another one of those names, I would say, it’s like Mount Rushmore of exercise and sports nutrition. Essential reading for anyone interested in sports nutrition. They have this fantastic setup working with these elite athletes. In this case, it was middle distance runners. And when I say elite, I don’t mean they’ve run a marathon. I mean these are people going to, or trying to make, the last cut for the Olympics.

Brad Currier, PhD: So they had this training camp as well where participants were randomized to MitoPure or placebo. After this four-week training camp, the group taking MitoPure—They would do a time trial before and after the training camp—There were significantly lower markers of muscle damage, an enzyme called creatine kinase, in the individuals taking MitoPure. And what’s curious is that despite their performance not changing, those individuals also felt like they were working less hard. It took less effort to work at that high level of performance.

Brad Currier, PhD: That’s kind of opened the idea that we need to take a closer look at how MitoPure, by improving mitochondrial function and also modulating the immune system, which we’ll get into, can really play a role in recovery from training. That’s what I’m curious about. The last was a weight lifter study, and I’m rambling. You can cut me off at any time.

Dr. Kara Fitzgerald: No, this is super interesting. I want to hear about the weight lifting study as well, but the damage is interesting. It’s funny, I was just making a note on it, thinking about a patient of mine who recently showed up. He’s been lifting a lot and his creatine kinase is elevated and I just want to confirm that he’s taking a gram. I think a gram is where I want all of my patients to be. In fact, I negotiate, as I was telling you offline, with my mom and getting her to toggle between—sometimes she’ll do a gram, but mostly she’s at 500, and I’ll take that. I’m cool with it. She’s taking it. I think that’s the most important thing.

Dr. Kara Fitzgerald: But I was curious about just the timing, like when we might expect to see some of these improvements. So the first study looking at the soccer players was six weeks in duration, and then the second was four weeks, which is really nice because it’s short. Did they publish at all on maybe the halfway point, if they saw significant changes? Like, how early?

Brad Currier, PhD: Yeah. So in those studies, no. Especially because when you’re working with athletes, you get such limited time, in that they’re focused on performance. So in those studies, no, there wasn’t a shorter measurement duration. But in other studies we have looked at, over the course of a few days, how long MitoPure stays in the blood. Really, the time course of adaptation is that after one month, that’s when we see the rejuvenation at the cellular level. We see that improvement in cellular energetics, the mitochondria. We see that upregulation of proteins and genes in the mitochondria and their function and health.

Brad Currier, PhD: Beyond four weeks is when we would start to see some of these beneficial physiological and performance-type impacts. Obviously, the soccer study was one of the shortest, and the runners were four to six weeks.

Dr. Kara Fitzgerald: Super short, yeah.

Brad Currier, PhD: But in the studies we’ve done with generally healthy adults of varying ages, after two and four months, that’s when we see improvements in things like muscle endurance, VO₂, and muscle strength. So it’s not quick. This isn’t a stimulant like caffeine where you’re going to feel it a few hours later. This is really trying to hit the central biology of why are we aging, why is our performance decreasing, and really rejuvenating that cellular health. It’s going to take time.

Brad Currier, PhD: So with the regular use of MitoPure over those days, weeks, and months, it will progress, from not just healthier mitochondria, to then that healthier mitochondria translating into these physical benefits.

Dr. Kara Fitzgerald: I just want to go back to the position statement you guys worked on and by any means possible, let’s get everybody moving. But before they’re moving, you know, so even before someone’s exercising, we want to prescribe MitoPure. I mean, honestly, I take a gram myself. I prescribe a gram really to everybody across the board. I think it’s that fundamental. My kiddo will take the gummies, and we haven’t mentioned it yet, so if you’re not aware, you can now get that gram dose in two caps in the new MitoPure Pro. And that’s on Fullscript.

Brad Currier, PhD: Yes.

Dr. Kara Fitzgerald: But I do think it’s important to just introduce it, you know, just get that party started. In fact, the patient I was just talking about earlier who was working with the trainer for osteoporosis started MitoPure, and I only started her at 500. I just needed to get her used to taking something regularly. And this has been an anecdotal report, she had energy. Her energy just jumped considerably, pretty quickly, with just the 500mg. In fact, it was her husband who was like, “Whoa, you’ve got a pep in your step.” He was the one who pointed it out to her. So that was kind of cool, and that helped to commit her to it. That helped to kind of put a little fire under her and initiate the training. Now we’re going to regroup there and move her to another setting for that. But it really helped to get the party started.

Brad Currier, PhD: Oh, super cool.

Dr. Kara Fitzgerald:  Isn’t that cool?

Brad Currier, PhD: Yeah, it is. It’s an essential one, for sure. Essential in the stack. What’s really cool, actually, is the first-in-human study of MitoPure. This was where they had people take it for a month. They were looking at the biopsies, really doing this safety assessment of it. What they saw in the biopsies is you get this gene signature of proteins being made from people getting the placebo, 500mg, or a gram and you see the increase in mitochondrial genes and proteins going up with increasing MitoPure after one month. But these are publicly available databases where you can look at how other interventions or populations look in these genes and proteins.

Brad Currier, PhD: There was a lot of overlap between the higher MitoPure dose at one gram and very active individuals of the same age. Where in people who are sedentary, the mitochondrial genes are downregulated. So there’s no replacement for exercise, let me be clear, but we were definitely able to hit a lot of that same biology at the mitochondrial level.

Dr. Kara Fitzgerald: Yeah. It’s extraordinary. And we think about bioenergetics, again, thinking about it through the lens of a clinician treating a broad swath of individuals struggling with certain conditions, what doesn’t have bioenergetic involvement? Like the ovaries, right? The highest mitochondrial-dense tissue. The heart, you know, right up there. I mean, you can probably list off the mitochondrial density of all the tissues. But then the brain, Alzheimer’s, Parkinson’s, these are all bioenergetic issues. So when we think about indications through a clinical lens of using the amazing discovery of Urolithin A, it’s why you end up seeing it being a part of everybody’s stack who I work with, and I take myself.

Brad Currier, PhD: Yeah. It’s increasingly discussed, but I think rightfully so, how we’ve got the biological hallmarks of aging. But in so many cases mitochondrial function can underpin these other hallmarks. In the case of what people might see in the clinic, a great example is mitochondria gets dysfunctional. And the credit goes to Gerald Shulman, who’s a great researcher in the States and has this beautiful work showing how mitochondrial dysfunction, with the toxins and reactive oxygen species it emits into the cell, actually impairs insulin sensitivity on the IRS-1 axis.

Brad Currier, PhD: What does that mean? Well, people become insulin resistant and certainly that has consequences for blood sugar, but there’s a lot else that insulin does, whether that be cardiovascular health, certainly, or blood sugar, and many other things. This insulin resistance being underpinned by mitochondrial dysfunction is just one example of how the mitochondria are the nexus of so many things that are critical to our function at the cellular level and, of course, when you extend it out, the whole organism.

Dr. Kara Fitzgerald: Are you going to start, or is it already happening, where trials are using MitoPure with certain conditions like heart failure patients, Parkinson’s, Alzheimer’s, infertility, and on?

Brad Currier, PhD: Yeah. It’s funny, actually, as you mentioned all those, the ovaries, infertility, brain, for a lot of these cases—

Dr. Kara Fitzgerald: Cancer, actually. I think there’s some cancer…

Brad Currier, PhD: Yeah, there’s great preclinical work for pretty much everything you just mentioned. But of course, translate it to humans. And we have some really exciting partnerships with leading academics where they’re running the study, we’re not. And a lot of times it’s important to recognize that MitoPure is a food supplement. It’s no replacement for exercise, just like it’s no replacement for what would be the most appropriate medical treatment for individuals with these conditions, based on their provider’s care.

Dr. Kara Fitzgerald: Of course.

Brad Currier, PhD: But we do have some studies going on. We have a few with cancer. We have studies being conducted by the National Cancer Institute in the United States, as well as another group in Germany that’s looking at it as an adjunct or an additive to Keytruda (pembrolizumab), which is the most prescribed drug in the world in cancer patients, to see if there’s an enhancement of the effect when we can couple that standard of care with MitoPure.

Brad Currier, PhD: Yes, in Alzheimer’s and Parkinson’s there are clinical trials going on in these spaces, and the interest is only increasing. I think that’s been something really cool to see. Obviously, I’ve only been at Timeline a couple of years, but especially for the group that’s been here for almost two decades since the start. At first, of course, a lot of the research was coming from Timeline because Urolithin A wasn’t really known. But even the last year alone, there were well over 100 publications on Urolithin A, and most of them are not done by Timeline anymore.

Brad Currier, PhD: So it’s really cool to see not just results verified by external and independent academics and parties around the world, but also expanded on because we are very proud and do quite a lot of research. We’re punching above our weight for sure. There’s only so much… So it’s great that, as a scientific community, you can see so many of these situations, pathologies, or other interventions being explored, because it comes back to MitoPure’s mechanism. When you’re targeting things at the cellular level, the benefits are numerous.

Dr. Kara Fitzgerald: You guys, by the way, are shortlisted for the XPRIZE. I’ll give you a little shout-out for that. That’s exciting as well.

Brad Currier, PhD: Thanks.

Dr. Kara Fitzgerald: Okay, so I have two more questions, and then we’ll wrap it up.First of all, I just wanted to circle back. And again, everybody, all the myriad papers Brad has referenced, will be linked to in the show notes. And if there’s some clearinghouse of some of the clinical trials going on, we’ll try to grab those and link over to those. I want you to talk on the weightlifter study because you brought it up and I’m curious. I know there’s somebody listening who’s like, “Go back to that.” So we’ll go back to that. And then I’m going to talk about your own stack, and then we’ll bring it home.

Brad Currier, PhD: Awesome. Yeah. So the weightlifters study, to put a pin in our earlier talks about weightlifting, but resistance training also might help there, and pull it all together. So this was another study done by completely independent researchers. The team here had no idea it was being done and all of a sudden it was just published. This group is one of the top sports science institutes in China, but they literally just bought the product and ran the study. They had a placebo that was adequate to match.

Brad Currier, PhD: This was a study in really well-trained weightlifters, so individuals who had several years of resistance training experience. They could squat more than two times their body weight, bench more than one and a half times their body weight. They’re well trained. And then these individuals, they were going through their regular standardized program across the entire population of people in the study for eight weeks. One group was randomized to get one gram of MitoPure, and the other group was randomized to get placebo in a blinded trial.

Brad Currier, PhD: After the eight weeks, what they saw was a few really interesting findings. One was a significant improvement in knee extensor strength. But the second, and the one that really stuck out to me, was an increase in a test called repetitions-to-fatigue. So outside of just maximal strength, this is one where you take a submaximal load. So if you imagine you can lift 100 pounds, we’re going to do this test with 70 pounds, and you’re just going to lift it as many times as you can. We’re going to count how many times you can do it.

Brad Currier, PhD: That repetitions-to-fatigue was significantly increased in the group taking MitoPure. So that was a really cool study published in 2024, I believe. So that’s kind of a pin on the sports studies, with more to come, I will say. We’re not stopping.

Dr. Kara Fitzgerald: No. You need to get into cyclists.So your stack. You have a short and sweet stack. I want you to talk about it. Is MitoPure in there, and how much? Then I’ll ask you some questions. So what is your daily stack? What’s a must-do?

Brad Currier, PhD: Yeah, it is simple. My daily stack is quite literally a multivitamin, MitoPure, and creatine.

Dr. Kara Fitzgerald: Right.

Brad Currier, PhD: That is it. The multivitamin and mineral is really just to cover my bases. Make sure that if the salad’s missing a couple of the veggies as normal, or missed entirely, that I’ve got those micronutrients that are essential. But creatine and MitoPure, we’ve talked about supplements where you can really unlock the potential of food that you couldn’t otherwise access. MitoPure and creatine are exactly that. So for me, those are the no-brainers on my stack.

Brad Currier, PhD: Supplementation is for either replacing a deficiency or adding a benefit. If someone’s deficient in vitamin D, if someone is deficient in XYZ, supplementation is a great option. Similarly, if someone’s not eating enough protein, supplementation is a great option. But once you’ve got those bases covered, the additive effect… There are very few supplements that add on to what we could otherwise get from food. Creatine and MitoPure. That’s my short list.

Dr. Kara Fitzgerald: I’m curious, what’s your grams per kilogram goal for protein?

Brad Currier, PhD: Yeah. So for me, I weigh 84 kilograms, and so for me, I’m trying to get in that neighborhood of 125 grams of protein a day.

Dr. Kara Fitzgerald: Are you religious about that?

Brad Currier, PhD: No, honestly. I think in part it’s because I spent so many years counting calories and macros, one from performance but then just studying it. It was cool, and you look at enough food logs in these studies, you get a pretty good sense. I still do a three-day diet log every couple of months to check in and make sure I’m calibrated. But also, my diet doesn’t change a whole lot in the sense that there’s a pretty set stack of meals on rotation. You know, we have these two or three that we’ll do this week, and we’ll swap them over for these two or three next week, and next month we’ll probably go back and do a lot of the same. So you get an ideal of how…

Dr. Kara Fitzgerald: You eat like a scientist. I have a CGM on right now, and that’s kind of how I hold myself accountable. But it sounds like you’re a little bit laid back with yourself after doing this for many years.

Brad Currier, PhD: Well, it shouldn’t be difficult for anyone. Don’t let it be overbearing. Know what the biggest fish to fry are, which is before you even think about counting protein, go to the gym. And if it’s not the gym, get moving. And if you do want to look at your food, in a lot of cases let’s get an idea of where our caloric balance is at. How much are we burning versus how much are we eating? That’s going to impact a lot for people. So make sure we’re taking the low-hanging and very impactful fruit before looking too deep at these nuances.

Dr. Kara Fitzgerald: Are you a fan of wearables? Do you use a wearable? I mean, I can get some idea with my Oura. Oh, and then I’ve got a Garmin on my bike, which is more accurate.

Brad Currier, PhD: Yeah. So the one for me that I’ve used most is the Whoop. The Oura Ring, admittedly, I haven’t tried. I’ve just read some of the research on it. But honestly, most of my friends and family around me use that.

Dr. Kara Fitzgerald: I’m not, like, a wrist person, so this is…

Brad Currier, PhD: You know, and I just kind of…I didn’t really care. But I’ve got two things on my wrist. I’ve got my Whoop and I’ve got my watch. So it was sure, maybe a little silly looking, but I liked it a lot. It was great for the sleep. For me, that was actually the big learning point. Whoop is quite good with sleep and they’ve done some work looking at it compared to actual sleep studies. Yeah, for me, I learned a lot about my sleep from using it.

Brad Currier, PhD: I think it’s a continually improving tool where we get an insight into how we’re doing on the day-to-day and how we’re trending over time. Certainly, like anything, it’s got limitations. But the wearables are definitely a space that I’m really excited to continue to develop.

Dr. Kara Fitzgerald: And just circling back to your idea of thinking about calories, it can kind of bring a little bit of insight into that arena as well.

Dr. Kara Fitzgerald: You and I were talking off air about creatine and basically just what you said was really down to earth, kind of refreshing. We just wrote a pretty exhaustive creatine blog, and we were happy that we agreed. My team was happy when I shared with them our conversation on creatine.

Dr. Kara Fitzgerald: Basically you’re taking five grams, so I’m going to just kind of say what you said, and then you can get in and do the color commentary. Five grams is cool. If you do have digestive issues, you can take that five grams and divide it out. You can do a loading, but ultimately you’re going to hit saturation at any dose. It might just take a little longer if you skip that loading or I guess if you’re taking  less than five grams, but you’re going to hit muscle saturation anyway.

Dr. Kara Fitzgerald: So all roads lead to the same point over time. Maybe the time is a little shorter. You also talked about monohydrate being where it’s at, and that’s where the ginormous body of publications that have convinced you to make this a part of your essential stack use monohydrate. And some of the newer, sexier molecules out there getting a lot of PR may shave bioavailability a little bit, so they’re absorbed more quickly. But to your point, again, all creatine roads lead to saturation at some point. So if the bioavailability is improved by 30 minutes, that’s not bringing us anywhere. We can all do basically what we need to do with regard to creatine. There’s no timing. Just do it. So speak to that. Did I get it?

Brad Currier, PhD: Yeah, yeah. Nailed it. Knocked it out of the park. I can go home. Yeah. Creatine, arguably, and I can say quite comfortably, is the safest and most effective supplement, period. Thousands of studies over decades showing its safety and its efficacy. When it comes to the purpose of creatine, I think for some of your listeners it might be of interest what creatine does. It’s actually an energetic molecule. What I mean by that is it improves our cellular energy where creatine is a shuttle.

Brad Currier, PhD: Our mitochondria make energy. Creatine brings it to the part of the cell that needs it. That’s mainly what creatine does. So by improving the cellular energetics, we can train a little bit harder and build more muscle, maybe improve cognition, as some research is starting to show. But how creatine works is by saturating the muscle, like you said, because 95% of creatine is in muscle, most of the rest of it in the brain and a few other tissues. By saturating the tissues with creatine, we can then have these benefits.

Brad Currier, PhD: How do we get there? Five grams a day, like you said. All the studies looking at this show that over four weeks you get there. If you do the twenty grams a day loading and then taper it down to five, can you get there a bit quicker? Sure. If you’re taking it consistently, three to five grams a day, after four or five weeks you will be there and you’ll be fully ready to go. Just keep taking it daily so that you keep that muscle saturated.

Brad Currier, PhD: Monohydrate is the… We talked about the thousands of studies. All the benefits are on creatine monohydrate. It’s the one with all the safety data. It’s oftentimes the cheapest. There’s no evidence that any of the new forms, the salts and whatnot…you’ll hear that, “Oh, it absorbs quicker.” And it’s like, okay, so it peaked in the blood ten or thirty minutes earlier. What does it matter? Well, it doesn’t. There are no studies showing that that’s more effective than creatine monohydrate. So yeah, creatine monohydrate is the only one for me.

Dr. Kara Fitzgerald: And I just want to ask you, for the brain energetics using creatine in cognitive impairment, would you go higher? Is there any rationale for a higher dose there? Are we still looking at five grams?

Brad Currier, PhD: So I have heard some folks talking about this. A great person to follow in this space is Darren Candow, who’s up in Saskatchewan, Canada, and Abbie Smith-Ryan, who’s in North Carolina. Abby Smith-Ryan was actually one of the co-authors on the ACSM position stand, but she’s done some really cool work in female-specific creatine usage and how creatine might actually benefit females more than males. So stay tuned to both of their work.

Brad Currier, PhD: Some folks will say higher doses, ten grams, maybe even twenty grams, to get some of these cognitive benefits. It’s too early to really say for certain exactly what the cognitive benefits are or what the best dose to achieve them is. As far as I know, I would defer to the leading experts in this field on that. But as far as I’m aware, what that great dose is for cognitive benefits is not well defined.

Dr. Kara Fitzgerald: Okay, cool. Well, we’ll keep our eyes open for that. And I do want to say, just from personal experience, you know, this is an N-of-1. I don’t prescribe twenty grams to my patients. Five grams is where it’s at, as far as I’m concerned. But when I was competing and doing higher doses, that’s when I did experience some of the water retention and so forth. So I’m just staying with five.

Brad Currier, PhD: Yeah, definitely. It would be quicker, and creatine is improving fluid balance in the cell, for sure. On average, when someone takes creatine, they think, “Oh, I’m going to get all bloated”. On average it’s like half a pound, if not less, of body weight shift you may see. So when we’re talking about someone who’s 130 pounds, 200 pounds, 240 pounds, like half a pound, we’re not going to be seeing this…

Dr. Kara Fitzgerald: I felt like I saw it though. It’s been a minute since I did this.

Brad Currier, PhD: No, you’re absolutely right. You’re absolutely right where it’s there, and you might feel it. Everyone’s unique. But I say that more to folks who might be worried about trying creatine because of that. Listen to your body, of course. You are the best judge of it. But the water retention—They’ve now done multiple studies looking at body water and how body water content and body weight changes with creatine supplementation, and it’s not as much as people think. It’s not enough to give people serious concern. Listen to your own experience, of course, and as you start supplementing, what it’s doing for you. But on the whole, most people don’t need to be worried about it.

Dr. Kara Fitzgerald: It’s not a big deal, in other words. It’s not a big deal. And the safety studies, to your point, are there and strong, and it’s safe. Okay, okay. That’s cool. Listen, this was a real tour de force. Thank you for staying with me longer. It was a lot of fun Brad. I look forward to our continued conversations.

Brad Currier, PhD: Likewise. Thanks so much.

Dr. Kara Fitzgerald: Did you love that conversation with Dr. Currier? Isn’t he awesome? This is my second time working with him and I always enjoy it because I always learn something. I appreciate how down-to-earth he is, actually, and his colleagues in this space bringing exercise to us and making the whole journey of resistance training less intimidating and very evidence-informed. I’m sure you’ve got some good tools to bring to the clinic on Monday and things to be using for yourself. And of course, it was fun discussing his stack, discussing the amazing research on Urolithin A, and we dipped into a good conversation on creatine, I thought as well.

Dr. Kara Fitzgerald: As always, thank you so much for listening. If this conversation sparked any ideas or shifts let me know. I love to hear from folks. I really do. It’s an important part of what we do, the community, being in contact with you. And again, please consider subscribing, leaving a comment, sending this off to a colleague or friend you think might like the content. And don’t forget to head on over to the show notes. The full transcript is there, all of the citations that Dr. Currier referenced today you will find there. Even the Instagram links will be over there for some of the sports scientist luminaries that we were talking about. And again, it’s all free. We’ll see you next time on New Frontiers in Functional Medicine.

Dr. Brad Currier is Manager of Clinical Trials at Timeline, a Swiss biotech company at the forefront of longevity science for over 15 years. With a background in elite athletics, he went on to earn a PhD in muscle physiology, where his research focused on how exercise and nutrition influence aging and performance.

Brad has led numerous clinical trials conducted around the world and published extensively in peer-reviewed journals. He is also the lead author of the American College of Sports Medicine’s new position stand on resistance training prescription, helping shape global guidelines for strength training and healthy aging.

Timeline Studies

American College of Sports Medicine (ACSM): Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews

Protein Metabolism Research Lab at McMaster Institute for Research on Aging

Accreditation Programs for Personal Trainers

American College of Sports Medicine (ACSM)

National Strength and Conditioning Association (NSCA) Special Populations Personal Trainer program

National Academy of Sports Medicine and Athletics & Fitness Association of America (NASM)

American Council of Fitness (ACE Fitness)

People Mentioned

Stuart Phillips, BSc, MSc, PhD – Instagram

Abbie Smith-Ryan, PhD

Eric Rawson, PhD, FACSM

Brad Schoenfeld, PhD – Instagram

Dr L.J.C. van Loon

Professor Louise Burke

Jamie Whitfield, PhD

Gerald Shulman, MD, PhD

Darren Candow, MSc, PhD

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Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial

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Bio Age Self Assessment Quiz

Younger You book

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