How to build muscle and stay strong at any age with Prof. Claire Steves and Prof. Tim Spector

For most of us, muscle loss starts in our 30s. It’s easy to think that you can combat this and stay strong into old age by strength training and eating plenty of protein.

Exercise and macros matter, but scientists are uncovering another important piece of the puzzle — a direct connection between your gut health and healthy aging. 

In today's episode, Prof. Claire Steves — a world-leading expert in aging and health — and Prof. Tim Spector explore the gut-muscle axis: How your gut microbiome influences your muscle health.

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Jonathan: Claire, do we only start to lose muscle mass when we're old?

Claire: No.

Jonathan: If we lose muscle mass as we age, does it increase our risk of bone fractures?

Claire: Yes

Jonathan: Do muscles release chemicals that affect our health?

Claire: Yes.

Jonathan: Is it true that a healthy gut microbiome helps to build healthy muscles?

Claire: Possibly.

Jonathan: Tim, can our gut bacteria communicate with our muscles?

Tim: Yes.

Jonathan: To support healthy muscles, should we aim to eat as much protein as we can?

Tim: No.

Jonathan: Claire, as we age, should we increase our protein intake?

Claire: Yes, with some caveats.

Jonathan: Can exercise on its own change the makeup of our gut microbiome?

Claire: Probably not on its own, but we do know that people who exercise, when they exercise, their gut microbiome changes.

Jonathan: And finally, Claire, what's the most common myth that you hear about muscle health and strength?

Claire: I think it is maximum protein equals maximum muscle health.

Jonathan: And it's not true?

Claire: It's not true.

Jonathan: One of my favorite things about doing this podcast is learning brand-new science direct from the researchers who are actually, you know, doing the studying, and research that just totally changes the way that I think about the world, and I think that this episode is going to be one of those times.

Listening to those answers, I find it a bit crazy to think that my muscles and my gut microbiome are linked, and even crazier to think that my gut microbes might actually be helping me to grow my muscles. If you thought that building muscles as you age comes down to lifting weights and eating more protein, you're about to find out that's only half the story.

When I think about muscle building, I think of my son, who's 18, going to the gym and proudly showing me his biceps.

Read next: What to eat after exercise, according to a nutritionist.

So if you're listening to this and you're not an athlete, you're not 18 years old, you're not hoping to look great without your top on, why should you even care about your muscles?

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Claire: Well, you really should care about your muscles because actually muscles are what's important for everything we do. Because even to get up out of the chair right now, I need to use my quads, and that gets difficult as we get older, actually. And so we can do a lot earlier in life to make sure we maintain our muscle function.

But also, our muscles can do good things for the rest of our body as well. It kind of influences how our brain works, influences all manner of different other organs in the body as well.

Tim: So it soaks up things like blood sugar and can help prevent diabetes. So lots of things you don't necessarily associate with muscles do have a role.

Jonathan: I think people listening to this, like immediately understand that you need muscles to get out of a chair. That makes sense, and that obviously becomes really important as you get older. But the idea that my muscles are having an impact on my brain or any other part of my body, that seems wild, and I don't understand it at all.

Claire: Well, it does seem a bit weird, but I think the other thing that we haven't talked about yet is our muscles really do impact our inflammatory system or physical fitness. Physical exercise really impacts how our immune system works, and that is probably something to do with the crosstalk with the microbiome.

But we know as well that people who have better physical function, better leg strength, for example, they have better cognitive aging. They have reduced risk of Alzheimer's, as you say, reduced risk of diabetes and so on. So there's a whole crosstalk between the metabolism, the brain, the immune system, and the muscles.

Read next: Inflammaging and the role of gut bacteria

Tim: Yeah, I thought it was really strange that grip strength is one of the best predictors of your cognitive change as you get older, and you think, "What's that got to do with it?" So it's really understanding that all these different organs in our body, which we've thought just had one role, are actually all part of this big organization that keeps us healthy.

Jonathan: I've got this model in my head of muscles are just something that sort of contract, and they pull things closed and open. I understand how that's related to your fitness, and I can sort of understand that being fitter is good for me in general. But I want to come back to that question at the beginning about chemicals being released by the muscles, and you said yes.

My simple model of they're just like a spring that, you know, pulls shut is clearly too simplistic?

Claire: Well, that's really interesting. So yes, it is too simplistic because I think obviously muscle is a metabolic organ, so it is producing chemokines, myokines. It's influencing the immune system. But I think also it's simple because you've forgotten about the neuromuscular junction.

So the muscle isn't just the muscle fibers, right? It's the muscle fibers and how they work together in teams called neuromuscular bundles and how the nerves then, like recruit and activate those muscles is really important for how the muscle actually functions. And then also the way that the muscle functions is dependent on other cells inside the muscle which kind of contribute to the health of those myofibers.

So it's actually a kind of system. It's not just single, single sorts of cells that are working together in the muscle

Tim: And Claire, some people get fat deposits- Yeah, exactly ... in the muscle. How does that change?

Claire: Yeah, so that, that's really important. So fat in the muscle, but also fiber, fibrous tissue in the muscle.

And remember that the muscles at the end, there's a lot of tendons at the in the ends of the muscles, which in young people, like your son, are really stringy and great. As we get older, they get much stiffer, and that affects muscle function as well. But you were just talking about muscle fat, so as we get older, we might, if we're lucky, maintain muscle sort of volume on a scan, but when you look clear- you know, in more detail, you can see that it's infiltrated with lots of fat, and that's not good for the muscle, and it's not good for the body as well.

Jonathan: And that brings me on to wanting to ask about how muscle is maintained, because I think we've all sort of got this idea now that you're supposed to go and do some exercise, you sort of strain it, and somehow this is good. But could you help us to understand what's actually going on in these muscles?

Claire: So I think what you're asking is about the balance, basically, in muscles.

Yeah. So we often talk about catabolism and anabolism in muscles. Yeah. So people who are sort of on anabolic steroids, for example, yeah, they are things that build muscle. Anabolism means building muscle. Catabolism, especially if you're maybe unwell, under starvation, maybe have cancer or something like that, we can see catabolic things happening where the muscle is broken down quite rapidly.

It's when basically the rest of the body is trying to use that muscle for nutrients to feed the brain and the heart and so on. So there's this constant balance in muscles as well as in bones where you've got growth, repair, and turnover happening, and that's what's changing as we get older, really, and also changing as we do exercise

Jonathan: And so does that only happen if I have cancer or I get really sick, this breaking down, this catabolism you're talking about?

Claire: No, so it's happening all the time. There's a dynamic balance happening all the time, and it's basically shifting the balance one way or the other. But yeah, certain conditions like starvation conditions or conditions like cancer can really, really shift the balance. It's basically telling the muscle to release all of that energy that's got stored.

Jonathan: We were talking about my son's biceps. Yeah. It sounds like this process is going on every day. Could you just paint me a picture of it?

Claire: Yeah. So as he does the exercises, he's gonna be straining that muscle, okay? And then there's gonna be a period of time when that strain of that muscle is actually, it's gonna be using the muscle, but it also might actually break down a little bit of the muscle in the process of doing it, especially if he's doing really high resistance training exercise.

But then that gives a stimulus to the muscle to then repair and grow more. So even though he, his, he might have an immediate sort of slight catabolism, then it's gonna create signals that it's then gonna grow his muscle. And because he's a young man and he has testosterone on board, that's gonna be quite an effective process that happens in him, so he can get much greater muscle growth as a man than, say, for example, if you had a daughter probably.

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And then also he's probably, you know, guzzling protein like many of these young people are, and that does help build muscle as well. There's no doubt about that. That's an anabolic thing, but only to a certain length, to a certain extent, and only in certain contexts, which I think we'll go onto later.

Tim: So someone older like myself, if I'm not exercising, generally I will be slowly losing that muscle because I won't be stimulating it enough. Whereas when you're young, you know, I look at pictures of when I was young, I didn't do much exercise, but I looked really fit. I have all these muscles. I said, "I don't remember doing any exercise. I look great." And now, you know, you've got to really struggle to not lose it. What's, what-

Claire: Yeah ... why is that? Yeah, yeah. Well, partly, I mean, that's super interesting, isn't it? Young people, they just move around a lot. They're just driven to move. We have a little bit less urge to move as we get older, which then unfortunately leads us to this kind of vicious cycle of not doing enough exercise, not doing enough stimulus to the muscle, and then the muscle's kind of gonna break down.

And so you see a massive difference between the sizes of an average man at the age of 20s muscle and the average man at the age of 70. You know, really massive differences in muscle bulk, and also muscle quality, 'cause the fat's infiltrated into the older muscle.

Tim: It's very depressing.

Claire: It doesn't have to be like that. So I just described what is usual between sort of different age groups. But actually we know from the Mass Cyclist Study within King's College London, which is a really great study, look it up, that actually if you really exercise your muscles, even if you're 70 or 80, you can actually get good muscles like a 20-year-old.

And, you know, they may not be quite as strong muscles as a 20-year-old, but certainly if you look on an MRI study, they can be as good, looking as good. So it isn't a completely depressing story. It just means that we just need to do more as we get older and not forget that moving is good

Jonathan: Well, that is very uplifting, and I definitely want to spend the second half of this show really talking about what you can do.

I'm already understanding, like the muscle is much more complicated than I thought. It's doing many more things than I thought. Could we talk for a minute about what happens if that balance has broken down? You know, we end up in this place where your muscles are therefore shrinking year after year. What happens?

Claire: Well, so unfortunately, you're able to do less, therefore you do less. It's not a great outcome.

Tim: Why is that a problem, doing less? Most people just say, "Oh, that's fine. I just sit by the telly and, you know, have a nice, comfortable life."

Claire: Well, at some point you might need to get up off that sofa, go make a cup of tea, and ultimately if your muscles and bones aren't very good, you can fall over and then end up in the hospital.

It's not, it's not a very good outcome. So I think, you know, definitely the end result of this sedentary lifestyle is not very good for our muscles and our bodies as it were moving, but it's also really not good for our brains as, as we alluded to before. We still need to be able to move around in order to do things, including be social, get about, get food, get, get things like that, even if you're gonna have a delivery to the door, whatever.

Ultimately, moving, keeping healthy, keeping muscle function well is gonna be important for whole body function.

Tim: I think it's even wider than that. I think because the muscles are involved in the immune system, the immune system is key to aging.

Claire: Yeah.

Tim: You're probably gonna age faster, and you're more likely to get things like cancer. So this is probably why there's this epidemiological association between sedentary living-

Claire: Yeah ...

Tim: and later increases in things like heart disease, cancer, you know, the major- Yeah ... killers, and Type 2 diabetes, and of course obesity.

Jonathan: This is all really obviously bad for you. I get the not being able to get out of the sofa, but how on earth do you end up getting cancer or diabetes or any of the rest of these things because of my muscles shrinking?

Claire: Well, it's not just the muscles shrinking, it's all of those stimulus that go onto the body which are helpful. But say, say let's take the immune system. Really good point, because our immune system's on the lookout for cancer cells, which could develop at any time in any of us, right? It's slightly more likely to happen as we get older because we have to have a certain number of knocks on our genome to get a cancer.

But our immune system cells are actually doing surveillance all the time and keeping most of those cancers, they're just killing them straight off. And if you have an immune system that's not working very well, then that doesn't happen, and that's when cancers can grow. So we know that there's a very strong relationship between obesity and cancer, and we also know there's a strong relationship between physical inactivity and cancer.

We know from epidemiological studies certainly that if we increase physical activity, we reduce the risk of cancer.

Tim: Yeah. So a lot of this is due to this immune function of the muscles that are interacting with all the other immune signals, and yes, they'll help the surveillance, the anticancer, but they'll also be sending signals to the brain.

If you've got lots of muscle, dampens down inflammation in the brain and is probably why there's also an association with mental health problems. So it has a really widespread effect. It's not the only thing, but it has this constant general factor that influences so many things in our body as we age.

Jonathan: It's really fascinating. You mentioned about obesity being bad for your health, and I think sort of everybody is aware of that. But what I'm struck by is you're talking about sort of these muscles and your muscle health as being different. So let's say that I'm just an average weight. I'm not overweight.

Does it still matter to me whether or not I have healthy muscles, or is it only because of its sort of the link here between, you know, not ending up living with obesity?

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Claire: Yeah. I mean, I think actually what's really interesting with physical activity or muscle function is that you can see a relationship all the way along the spectrum.

So you can see even going from very minimal levels of muscle function to just a little bit better, you can see beneficial effects on, say, for example, cognition outcomes or immune outcomes. But you can also still see them in those master cyclists and things like that. So it's a, it's quite a strong relationship that's working all the way across the spectrum.

I think there is a point where you get to sort of super athletes who are really, really pounding their body really hard, and I think that's probably over and above what's needed. But ultimately, you know me, definitely, I'm normal body weight. I definitely need to be looking after my muscles.

I'm probably not doing enough even though I am trying.

Tim: Yeah. No, I think that's right. And I think comes back to this myth that we still think about is that exercise is the number one way to lose weight, right? And we know that, we know that's not true. It has some effect in keeping your weight off if you've, you know, you're on a really good diet, but diet is so much more important.

So we mustn't confound those two factors. And I think what we're seeing is that, yeah, muscle is a very independent factor to just putting on fat on its own. And that's why these studies when they look at overweight people who exercise, they-- you can offset quite a lot of the problems of the obesity with exercise.

So we need to be thinking about muscles, not just about our weight. I think that's the key message here.

Jonathan: I'd like to talk next about sarcopenia.

Claire: Mm-hmm.

Jonathan: Could you help me to understand what that is and why we need to care about it?

Claire: Certainly I can. People have known about sarcopenia for hundreds of years. Shakespeare describes sarcopenia. If anyone knows the all the world's a stage speech, when he starts talking about older people, he says something about basically calf thickness. He says, "Shrunk shank," I think that is.

Tim: Shrunken shanks.

Claire: Yeah, exactly. He's making the first sort of reference of what sarcopenia is. It's basically you've got small muscles. We now agree that sarcopenia isn't just about muscle bulk, okay? This is really important. It's also about muscle function, strength. So when we sort of diagnose sarcopenia, we always look at muscles mass, as it were, and also muscle function because, of course, you could have a big muscle, but it's infiltrated with a lot of fat and it doesn't work very well.

So sarcopenia is a combination of like the muscle bulk and the muscle function, and there's cut points where you say you're below a certain level and that means that you're sarcopenic, which means loss of muscle.

Tim: The way to think about it, a lot of people know about osteoporosis. It's a sort of similar idea that you're losing bone and bone mass, and there's a certain point where you start to get at risk of fractures and things like this.

So sarcopenia is the same thing for muscles and is a range. There isn't one point at which it happens, but your risk of everything just gets more as you get less muscle, and it varies at different ages, just like those bone measures osteoporosis. So I think in the future we will have, like we have bone density scans, we have sarcopenia scans or sarcoporosis scans. I'm not quite sure what they're called.

Claire: Yeah. Yeah. Well, indeed, like the DEXA scans, a very scan that we use for looking at osteoporosis, you can look at muscle bulk, but what's interesting about that is that that's not enough to get a diagnosis of sarcopenia because of this thing. Actually, some people have quite thin muscles, but they're really well functioning muscles, right?

And they can do a lot with them. In fact, I'm one of those people. If you look at me in terms of my muscle size, it's actually quite small. I almost look like I'm on the threshold of sarcopenic, but I'm actually quite strong 'cause my muscles are working well together and functioning well as a unit, and that's the other thing in sarcopenia that we really measure.

Jonathan: And so is sarcopenia meaning my muscles are below some, like, absolute level or is it about the fact that my muscles sort of year after year are shrinking?

Claire: No, it's the level actually. In medical sort of world, we often dichotomize things because we wanna know whether we're gonna treat something or we're not gonna treat something, and so we make a threshold, but ultimately we know that that threshold occurs because of gradual changes.

So at some point someone will go across that threshold.

Jonathan: So if someone has sarcopenia, then it means that their muscles have fallen below some level at which it's now like a risk to their health?

Claire: Exactly, and we really need to treat it, and we are working hard to work out ways to treat it and we know that muscles, even once they become sarcopenic, can be improved.

Jonathan: And so it sounds like you're saying this doesn't happen sort of overnight. It's not sort of like I go from having a really good level of muscles and just in a year I sort of go to having this-

Claire: Oh, well, that's really, really interesting, and actually it can happen almost overnight. In fact, it's not overnight, it's about four days. If you have four days of complete bed rest, studies have shown you can absolutely massively, I can't remember the amount, but it's really shockingly reduced.

Jonathan: Four days?

Claire: Yeah, four days. If we go into hospital, for example, and we're on ITU, we're completely paralyzed, say, for a week, our muscles will massively reduce, and that's a real issue for when we want to then recover

Jonathan: So let's assume that I'm not in hospital. I haven't had to have bed rest. Is sarcopenia something normally that only much older adults need to worry about? You know, is this something that I start to worry about in my 60s, 70s, 80s?

Claire: It's pretty unusual for somebody who is really young to get sarcopenia. People say sort of 40 is when muscle bulk starts, but I think it probably happens earlier than that.

Tim: I think it's in the 30s, isn't it? It's a bit like, but your bones peak at about 30 and your muscles probably similarly.

Claire: Yeah.

Tim: And then I've seen some data showing you lose 2 to 5% of your muscle every decade.

Claire: Yeah.

Tim: So it's why it's important, both in your 20s and 30s to build up as much as you can-

Claire: Yeah

Tim: and then try and reduce the amount you're losing it.

Jonathan: So that's quite scary. It reminds me of some of the podcasts we've had talking about dementia and the fact that these risks start, you know, all the way back into your 20s, but it's sort of invisible or heart disease similarly like. And so now you're saying it's the same sort of with my muscles.

Who's most at risk? Does everybody lose 2 to 5% the same or?

Claire: No. So I think there's several differences. I mean, first of all, it's about what diet you have. Some people still have really too little protein to keep muscle function. So that's one thing. The second thing is around sort of physical exercise and putting that physical stress on.

The third thing is probably about sex actually. You know, women are much more at risk of sarcopenia than men, because they don't have the helpful testosterone on board to build muscle. And then like diseases, so we've already sort of talked about the muscle effect on diseases, but there's also disease effects on muscles.

So the key ones that are really like obvious and big are chronic bronchitis, which might be because of smoking, but it also seems to be that is a muscle condition actually. And the second one is diabetes. So people with diabetes find it much more difficult actually to build muscle.

Jonathan: So I'd like now to come on to like your really exciting research, Claire, about the links between gut microbes and muscles and how that might help me stay strong. Because if I thought the links between muscles and my brain seemed wild, like the idea that there is, I am told, a gut muscle axis. Like how can muscles possibly be linked to gut health?

Claire: Yeah. Well, that's a really good question. I think one of the things we need to unpick here is this idea of anabolic resistance, and I think that's really key. We talked earlier about anabolism building up muscles. Yeah. So the anabolic steroids or like testosterone helps you build things, right? And catabolism being the other way around. So anabolic resistance means you're giving protein, for example, to say somebody, an older adult or somebody with diabetes or obesity or somebody with a poor gut microbiome and doesn't make any difference to their muscles.

They don't put on muscle bulk. They don't increase muscle function. And that's kind of curious. Why is that the case? And actually in older adults, this came apparent sort of about ten, 15 years ago. People would give the same amount of branched chain amino acids, leucine, for example, to young people and they would see an increase in their muscle bulk.

And they did the same to older people and they didn't see. They needed more protein to get the same benefit in older people than younger people. And that's when this kind of like concept of anabolic resistance came in. So then we started to think, well, how does anabolic resistance happen? And we've got a number of different mechanisms that we think might be key.

And funnily enough, many of them kind of come down to the gut microbiome. So things like inflammation. So we know that one of the key things that is really important about gut microbiome is its interaction with the white cells in the gut, training the immune system, reducing inflammation, maybe also some evidence of a good microbiome protecting against, if you believe it, leaky gut, so the leakage of microbial compounds into the blood, which then causes a storm of inflammation.

So a gut microbiome can help inflammation. It also can help metabolism, insulin resistance, which then also helps those muscle cells take on that protein. So there's a whole web of things that relate the gut microbiome to muscle function and seem to be explaining why some muscles resist anabolism.

Jonathan: Do we now understand specifically anything about what our microbiome is doing that leads to that improvement in muscles? And you sounded like you were saying inflammation was maybe an important part of that, if I understood rightly.

Claire: So I think inflammation is definitely an important part of that, and we know that from studies where we've done direct microbiome interventions and seen changes in inflammation, and we also know that from studies where we know that changes in inflammation relate to muscle function.

We don't have that many studies showing a very clear link between a microbiome intervention and muscle function. We tried to do that actually with a trial within twins, and we, in 12 weeks, we didn't get a clear effect on muscle function, although everybody got better. So it was difficult to tell the difference between the intervention and the control.

But there are some other studies that do show that, and there's some really interesting new work showing that it may not be just about inflammation, it may also be about other functions actually within the muscle cells that are really key. There's some early work showing that mitochondria, which are the sort of like energy powerhouses of cells, which are really important in muscles, seem to be affected by changes in the gut microbiome. So that's a really interesting angle.

Jonathan: And my team said I should definitely ask you about short-chain fatty acids.

Claire: Yeah. So short-chain fatty acids are metabolites that are produced in the gut by the gut microbiome, in particular by friendly bugs that digest complex carbohydrates principally and produce short-chain fatty acids. Now, short-chain fatty acids have several major roles.

Firstly, they are things that other microbes that are also beneficial really like. So the bugs that create those short-chain fatty acids help to foster a very diverse microbiome. The second thing is, is that short-chain fatty acids are a key nutrient that the enterocytes, so the barrier cells within the gut use for their energy stores.

Yeah. And the third thing is that short-chain fatty acids have direct effect on the immune system within those Peyer's patches, the white cells that circulate around the gut, and then can have roles further on, further abroad into the brain and in the muscles as well. So short-chain fatty acids are pretty key, and we know that they can be changed by having a good gut microbiome.

Jonathan: And is there a link between them and muscle health that you were talking about earlier?

Claire: Yeah. So I think there is. I must say that I have not been able to like in, within my experiments, sort of like deeply look at that, but others have shown links between short-chain fatty acids and muscle function.

Tim: Yeah, I'm sure there's more than one mechanism, isn't there? I mean, there have been some clinical trials where they've done resistance training, so, you know, weightlifting for people who weren't doing it before. So middle-aged people. And I think it was a German study of about 150 people where they did couple of months of doing this and looked at their changes in their gut microbiome.

And they didn't see massive shifts, but what they did see very clearly was big increase in the anti-inflammatory gut microbes. So these things like Faecalibacterium prausnitzii and Roseburia-

Claire: Yeah ...

Tim: that come up time and time again, and that means that the gut is actually helping the immune system and sending out chemical signals to the muscle to say, "Actually, calm down, you know, let's reduce the inflammation," and so it can presumably work more efficiently and get over this anabolic resistance.

And that's probably one mechanism why it works, which is interesting because this is people who weren't doing cardio, so they weren't doing anything else, were just doing weight training. And I think that's suggesting that certainly inflammation's one major thing, but we know that they're all related, so your short chain fatty acids.

There's also branched-chain amino acids. These little mini proteins, I guess you could sort of describe that, that are part of this whole protein process, and they can be converted into lots of different things by other gut microbes. And it looks like the state of your gut microbiome will determine how well you can use this stuff that comes in through your diet, convert them into these branched chains and either produce them as fatty acids or as carrying on to build proteins.

And we don't really understand the whole story yet, but it seems like it's a complex picture. But undoubtedly, the gut microbes play a very big role in all the signals that your muscles are getting to either make muscle or to lose it.

Claire: Yeah, that's right.

Jonathan: Does this mean that supporting my gut health and particularly, like, my gut microbes can support my muscle health as well?

Claire: Yes. I think that's really clear. And this comes to sort of like really basic studies where we've looked at, for example, the diet that people have and then their muscle function. Yeah. And we can see that actually having really healthy diets, like having good Mediterranean diet, for example, can influence muscle function.

We showed that with a study looking at leg strength, leg power, and it's a pretty clear relationship. It's not completely explained by inflammation. So there may be other factors like short chain fatty acids that are working.

Jonathan: Could you tell me a bit more about that study? It sounds fascinating. So you're saying you actually looked at the impact of diet on people's strength?

Claire: Yeah.

Jonathan: Not taking them to the gym, which seems like the obvious thing, but actually feeding them different food.

Claire: It was a study within the twins cohort, which Tim and I work with, and we looked at the relationship between Mediterranean diet score and leg explosive power, which is a really good measure for function of your biggest muscles in your body, your thighs basically, where you get somebody to do an emergency stop with a power rig and really look at how much power they can exert really quickly.

And we saw a really strong relationship between a Mediterranean diet pattern, higher score on that, much better leg explosive power. It was a really big study and certainly, probably the first really big study to show that. And we tried to look to see whether that was all explained by inflammation using high sensitivity CRP, which is one of the measures we use to look at that.

And we didn't see that explained all of it. So we don't know from that study what exactly explains this relationship, but it's clearly there. Interestingly, when we've looked at gut microbiome, we haven't seen a very clear relationship. And I think it's really interesting the study you talk about, which I think it's a great study where-

Tim: The German one.

Claire: Yeah. Because that shows that the gut microbiome changed in response to resistance training. But I'm not totally sure that that's because a direct effect of like the muscles. I think that might be an effect of the muscles reducing inflammation. So we know that resistance training reduces inflammation.

So then if we actually have reduced inflammation, actually our gut microbes really like that. There's this really nice cycle whereby muscle function means that actually our microbes are healthier, therefore our microbes can help our muscles and so on and so forth.

Jonathan: Coming back to this study that you were describing between Mediterranean diet and strength, you're saying that the people who are eating much closer to this healthy Mediterranean diet actually had a lot more leg explosive power-

Claire: Yeah.

Jonathan: which I love as a term. And you're interpreting from that, that the diet was improving their gut health, and that was then leading to this improvement across their health overall, and therefore actually improving their muscles?

Claire: Yeah, so that's a really good point, 'cause we can't really, from that sort of study, really say that it's the diet that's improving the physical function, because that's an observational study.

So to be able to prove that kind of thing, you have to do intervention studies. And there was a really amazing study on Mediterranean diet called the New Age Study, which was done a few years ago, where countries, I think it was five different European countries that all took part in this, including the UK.

They did it for a year, Mediterranean diet, and they saw that people who took on the Mediterranean diet more had better muscle function and better bone health, funnily enough. We saw that within that intervention study.

Jonathan: So in that study where they changed diet, the people who changed their diet more-

Claire: Yeah

Jonathan: improved their muscles and in fact improved their bones as well. Yeah.

Claire: They weren't sent to the gym. The only thing that changed with them was their diet.

Jonathan: That's extraordinary. Do we think there's like a particular species of microbe in our guts that's like a specialist in growing my muscles, and so it's like feeding this one particular sort of magic muscle bug that I need to do? Is that what's going on here?

Claire: I think that the microbiome is a community job, okay? It's not about single bugs. It's about communities, an ecosystem that's working well together. And I don't think it's likely to sort of like pinpoint a single species. And I think there's also a lot of overlap in the microbiome.

So you might find that sort of all the different functions are needed, but doesn't matter who does the job. Do you agree, Tim? Yeah.

Tim: I see the microbiome really as an organ that signals to the rest of the body when all the omens are good. You know? There's like everything out there is pointing in the right direction.

You can now grow and be healthy and produce more. Or it sends signals of famine and impending doom, and it says lock down and get rid of your muscles. Send everything to your heart and your brain to protect it. And I think this is what is going on in these scenarios. So that's what we want, is a nice calm gut that's sending all the right messages to the rest of the body saying, "Yep, to your heart, to your muscles, be healthy.

You can... It's a good time to grow. You know, harvest is good. Get on with it." That's my sort of current view of the gut.

Jonathan: You're saying the microbiome, because it's seen all the food is sort of saying, "Hey, everything is really good. We're getting all of this great nutrients we need." And so it's sending signals to the rest of the body saying like, "Keep your inflammation low, you know, grow. Everything's good." Or alternative is like, "Wow, all I'm seeing is McDonald's. This stuff is terrible. You know, lock down and protect yourself because I, I dunno what's going on outside there in the world, but somehow we're missing all this stuff that we'd really like to be getting."

Tim: Yeah, that's right. And it also is reflecting not just the diet, but also other diseases and things that are happening, 'cause it's picking up other signals. It's a two-way process, but a lot of it is coming from the diet, the outside world, what it's seeing.

Jonathan: Got it. So it's not only the outside like food. The microbiome is also responding to like the signals inside your body?

Tim: Yeah, because most of our immune system is around our gut, so in the same way you're feeding the outside world is through the gut and the diet and pollution and everything else. But things happening inside the body, whether you have allergies, immune diseases, whatever, coming from the immune system or, you know, presumably if you have four days of bedrest, that sends signals to your gut to upset your gut through the immune system.

So it's a two-way process, but it's all about signaling, I think, to the other organs in the body, you know, green light, amber light, red light. And when things are bad, it's definitely a red light, and that's often caused by bad meals

Jonathan: Claire, you mentioned, I think earlier, that there is messaging somehow coming from the muscles to my microbiome. It's not only the other way around. Do we know anything? Like, how can that even happen?

Claire: The easiest way, I think, is to think about it as, muscle function affects the immune system through myokines and cytokines that muscle releases, actually. Muscle releases a whole range of different sort of small chemicals that affect the rest of the body's systems.

Tim: And they would get into the immune system, and that's how they would connect with the gut, isn't it? Yeah,

Claire: yeah. But also, I mean, there are trophic factors as well that muscle releases. Remember we talked about your son or whatever, growing muscle, you know. Ultimately, when muscle is in that growth phase or change phase, it's producing hormones.

It's telling the rest of the body what it's doing. And then it also is probably telling our appetite centers and so on what to do, what to eat, how to then, like, work together with the muscle to enable growth, for example.

Jonathan: That's something maybe about feeling tired. One of the things I definitely notice is I do the gym. If I've done a good session, like, I get a sort of temporary high afterwards, and then a few hours later, you know, I'm at work in a meeting, I'm like, "Oh, I feel really tired. I think I need a nap." So there's some sort of linkage I feel from this exercise and I guess from these muscles afterwards.

Claire: Well, it's fascinating, and there's something really interesting there about how we exercise and how we eat and how we sleep.

Those things going together in the right order kind of like can lead to less feeling of fatigue. I think actually, if you do it right and get all the stars aligned, then actually it can make you feel very energized.

Jonathan: Any top tips for that?

Claire: Well, I'm really interested in intermittent fasting and then exercise and then activity. I think that combined with good exercise in the morning in the fasted state helps me to keep much more alert and alive. I stop eating at eight o'clock at night, and then I don't have anything until probably midday I can let myself eat.

And then I don't eat something really big then. I eat, you know, loads of veg and salad and fruit. And in that time, I do some exercise in the morning, just like a brisk walk, and I stretch. But what I want to be doing, and this is my new sort of resolution from now, is I want to be really doing resistance training, sort of like basically sit-ups and press-ups in the morning. I still can't do a proper full press-up properly, but I'm trying my best.

I'm 51. You know, I need to be looking after my muscle health, and actually, no, I don't think I'm doing enough at the minute.

Jonathan: In addition to the exercise and how important that is for your muscles, I'm curious why you've decided that you want to do the exercise sort of before you've started to eat for in the day. Is there any reason why you're doing that?

Claire: Well, so it's partly because of just logistics. That, in fact, is the main reason. There's some interesting science about this coming out, so I'll be keeping my eye on that. It does have to fit into life for most people, and so this is what I sort of say to my patients, Jonathan, is, "Do it when you can do it.

Let's just really try and be active as much as we can and combine sort of aerobic-type activities, but also resistance training activities, which don't have to take too much time." That's the good thing about them.

Tim: I think it's breaking this rule. I mean, we were always told you must never do exercise without having a breakfast, right? It was terrible. You'd faint or you wouldn't make it, and that's clearly absolute rubbish. I always exercise before I've eaten. I'm like you, and I much prefer it. I now do a bit of resistance training, which I didn't do a couple of years ago, and I just fit this in. You don't really need to do 10, 15 minutes, a session three times a week, and I think it is helpful.

Jonathan: I'd like to maybe spend the rest of the podcast now talking about specific advice for what people can do listening to this. Do I only need to think about a healthy diet when I'm much older, because that's the point when my muscles are starting to really become a problem?

Claire: Well, no, I think what we've been talking about is the fact that this is a lifelong thing. I think thinking about it in your 20s or even actually as a child, I mean, one of the things I do is try and educate my kids because I want to set up good habits. So I think there's never too early to start to change your diet into being more healthy.

Jonathan: And does it also mean that if someone listening to this is really serious about going to the gym and they are eating lots of protein, does that mean they aren't gonna get the full benefits of their exercise if they aren't eating like a sort of a healthy diet around this?

Claire: Protein is important. We have to eat protein in order to have our muscles healthy. And as I said, older adults might need a bit more protein than younger adults because of this anabolic resistance. But definitely chugging lots of protein drinks or eating exclusively protein is not gonna do anything helpful for your muscles, partly because basically that's then just gonna be used by the body as extra energy.

It's not gonna be used for muscle growth, it's gonna be more calories basically that's going into the body and the body's then utilizing. And secondly, it's just gonna be pooed out basically. People aren't gonna absorb all of it. And there's some evidence that really high levels of protein actually are detrimental.

We've seen that actually, that if people are eating very high levels of protein, actually their muscle function over time is worse. Is worse? Yes. Is worse than if they were eating the right amount, which is between 1 and 1.3 grams per kilogram per day. But if you're eating a lot more than that, it appears that your muscles are not any more healthy, but actually probably less healthy.

And that could be because actually you're exclusively getting your calories from those protein sources, and you're actually not eating all the other things that are gonna help your gut microbiome and everything else as well.

Tim: Yeah. As we always say, it's instead of what?

Claire: Yeah.

Tim: It's really hard to go above 20% of all of your intake in protein. So we naturally revert back to fats and carbs. So it looks like we've got a sort of built-in system most of us

Jonathan: When I go to the supermarket, everything has a label on it now saying added protein or high in protein. I imagine lots of people like me have ended up a bit confused about really what they should be doing.

Tim: People can reassure that most people are already getting enough. They don't have to worry too much about it. As a rough guide, if you know what your weight is in kilos, as long as you're getting more than one gram of protein per kilo, you should be doing okay. And all of these extra drinks and things you don't need, and usually they're giving you ultra-processed contents, extra chemicals, additives, sweeteners, nothing really nutritionally useful in it.

I don't think you need to be eating meat every day. I don't. I have meat once or twice a month, and my protein levels are fine, but my vegetables are high in protein. So I'm eating lots of beans and legumes. I'm eating mushrooms. Plenty of fermented foods from dairy have lots of protein in them, and you might sometimes have tofu and occasional bits of fish.

They're all fine. So I think vegans have to be a bit careful, and they should be carefully working out what their protein levels are, and some do end up being deficient. But for the average British person, yeah, I think if you are cutting back on your meat and dairy, you've got to just make sure you're filling your plate with all those plants that have so much protein to offer as well as fiber. And as Claire was saying, it's not just the protein, it's the other things that your microbiome needs that's really important.

So all those- that diversity of plants, that keeps the microbiome going well, which makes you more efficient in the way you make protein and muscle.

Claire: Yeah. I definitely second that. And I think the other thing is, is that different plants have different sorts of protein in them, and what's really important is that you combine those different sorts of plants. So, you know, you always have some cereals, for example, whole grain cereals, with some legumes, which then gives you the same sort of protein that a meat would give you. I think that's one thing about meat or, say, for example, eggs, really great source of protein, is that it's got everything in that single source.

So that's why some people have preferred that. But you can definitely do the same with plant-based proteins.

Tim: And realizing that, knowing a bit more about nutrition will tell you that having pasta rather than rice is much better way to get protein into your diet, or wholegrain pasta gives you even more protein than, say, something like white rice or potatoes.

Jonathan: And so are these just examples of foods that are high in protein that aren't sort of like my protein shake or red meat, or are you actually talking about foods, like, specifically that should help to maintain my muscle strength because of what we've been talking about earlier in this show?

Claire: So they're, I guess, a combination. So those things like whole grains and legumes are-- they're gonna help your muscles, but they're also gonna help your healthy gut microbiome. Whereas having sort of a beef burger or whatever is only gonna do the one. It's not gonna do both. But I think the other thing that's really interesting about protein is that lots of studies that look at protein and muscle function really focus on muscle bulk or certain characteristics of muscle.

But when we look at muscle function as a whole, it is a neuromuscular thing. And so we know that diets that impact the brain, which is really important, brain and nervous system, really important for muscle function actually. It seemed to be slightly different, and that's where some of these other things, you mentioned fish.

But the other aspects of, say for example, a Mediterranean diet. It's high in whole grains, high in fiber. It's high in fruit and vegetables. It's really high in things like extra virgin olive oil, which seems to have loads of polyphenols in it, which might be what's key. Nuts and seeds, and then fish. So fish being a component of the Mediterranean diet, which is quite probably quite important for brain health.

Tim: And not much pasta or pizza. So it's not what people always imagine the diet to be.

Claire: Yes, exactly. So those nuts and seeds and whole grains and legumes, which are really strong in the Mediterranean diet, those are all really good sources of protein, and they are also things that are gonna help your gut microbiome, but also particularly your brain and nervous system health, which is really important for healthy movement.

Then the polyphenols, that's probably super important for your gut function, but it's also really super important for nervous system function, and that neuromuscular bundle, that healthy nerve recruitment of muscle fibers.

Tim: I think what Claire's highlighting is that we need to always look at these organs not as alone, but as part of a system. They're all connected. So if we go, as we always do in nutrition, very reductionist, and say, "I've just got to have this artificial protein that's gonna feed this particular bit of this muscle", you'd be missing a lot of the picture. You've got to be feeding the whole organ and its connections. And so the idea that muscle is connected to the immune system and the nervous system and the gut, you've got to look after all of those if you want to be really maximizing your benefit for muscles.

Jonathan: You could think I've got my car, so I've got to make sure the tires are in fantastic shape and all sorted now, and that's sort of my protein is gonna make sure my tires are really in great shape. But actually, if I don't fix all the other components of my car, then that's what's gonna cause me to run off the road when I turn a corner.

And so I think what you're saying is the protein is really important for growing the muscle fiber, but the whole thing is really affected by my overall immune system health and my low inflammation. And so as I'm thinking about what I'm eating, that's why I have to get all those components to work.

Otherwise, it's like I've fixed my tires, but I forgot to make sure the steering wheel actually moves. Is that-

Claire: Yeah, I think that's a great analogy. It's a complex system. Yeah.

Jonathan: And Tim, can you paint me a picture for my son of what is going on inside him if he is on that sort of red meat and shakes diet?

Tim: Yes, so it's a bit like people going on keto diets or carnivore diets. Short term, they might feel slightly better. You will see improvements in your muscle if you're young and you're exercising, but only if you're exercising at the same time. But gradually over the weeks, you'll see your gut microbes decreasing in diversity.

Some of the good ones that are only thriving on these fibers will be dying off, and they'll be replaced by these meat and fat loving ones that are generally pro-inflammatory, that then produce pro-inflammatory chemicals that stimulate your immune system and might eventually lead to, you know, more brain fog and you acting a bit more slowly and eventually getting more tired.

So long term, you're doing some damage to your gut and the rest of your body at the expense of building up big muscles.

Jonathan: That doesn't sound like a good place to be.

Tim: No. What we need to find is a happy medium by which someone who does want to be sporty and have big muscles also needs to remember to look after their gut and they still need to have that same diversity.

Jonathan: So we talked a lot about diet. But I'm pretty sure, Claire, you're gonna tell me that nonetheless, that isn't enough to keep my muscles healthy, and we also need to do exercise.

Claire: Yeah. Yeah.

Jonathan: Are all forms of exercise the same in terms of the effect on our muscles, but also are they all the same in terms of their effect on our gut microbiome?

Claire: Resistance training is really interesting because it's a really good way to build muscle. It seems to really stimulate the muscle in a way that some other training methods don't. I think resistance training needs to be part of the package. But in the same way, a bit like the diet sort of has to have a bit of variety in it, I think it's a good idea that your physical exercise regime has some variety in it.

Getting your heart rate up, getting a bit sweaty, being a bit breathless in whatever you're doing, even if it's just walking briskly up a hill. Try and get out forty-five minutes, three times a week. Old relatives as well, they really benefit from balance training, sort of strength and balance. And that's partly because balance is sort of really super important for function in later life and helping prevent falls. And that requires slightly different exercise regime.

Jonathan: Tell us what you do, Tim.

Tim: Yeah, I used to just go for a run or go for a cycle. I didn't do anything else. And now I'm particularly worried about dementia and cognition problems. I've gone for this diversity of exercise, on the one hand, to sort of make sure that I'm looking after my heart and my muscles, but also looking after my brain because there's some evidence that the more different things you're doing, the more you can keep all the different bits of your brain active.

So this morning, I did some yoga. Two days ago, I did some Pilates. I'll get on my Peloton bike another morning. And I would sometimes do exercise classes with weights. And you know, I'm obviously walking and in summer I'm doing a lot of swimming. And as you said, balance becomes increasingly important as you get older.

So can you stand on one foot? Can you get off the floor without using your hands? Some of these things are actually really important and-

Claire: Yeah, yeah. The really good one for everyone to do, everyone do this from now is, stand on one leg when you're brushing your teeth and do some squats if you can. If you can't do squats on one leg, just do it with two legs. Squats while you're brushing your teeth. That's probably enough to really build your muscles actually, if you do it every time you brush your teeth.

Tim: And it probably also helps your brain as well, doesn't it? Yeah, yeah.

Claire: The other thing really want to emphasize to people is stretching as you get older. Stretching is super brilliant at reducing the risk of injury when you're doing exercise. And it's also really good at stopping sort of those awful things like back pain that stops you moving around. If you make sure you're stretching preferably every day, doesn't have to be for very long, but it can really make a difference 'cause our tendons just get so much less stretchy as we get older.

Jonathan: Finally, Claire, for someone who's listening to this and is like, "You know what? I want to do more to support my muscle health now," what's the one sort of thing that you would say, you know, start today?

Claire: Those squats while they're brushing their teeth.

Jonathan: Tim?

Tim: I would say do something as soon as you wake up. Just five minutes stretching in the morning before your brain can say no. And get into a habit of doing something different every morning.

Jonathan: Amazing. I'm gonna try and do a quick summary. And the first thing that comes to mind is muscles are crazy more important than I'd realized. So apparently they help prevent cancer, they help prevent me getting dementia.

I mean, who knew this stuff? I thought they were just for walking around. There's this amazing study that you did, Claire, where you said that people who are following the Mediterranean diet actually have more leg explosive power. And I like the idea of having leg explosive power, but the idea that what you eat could actually change this is also remarkable.

You need to do something for muscles, so you need to do some exercise. And sadly, over time though, these muscles are falling away, and this starts only already in your 30s. I think you said, like, 2 to 5% is being lost every decade. And so unless we really do something, then later in life it's really gonna prevent us having quality of life and maybe even have, you know, sort of life-altering fall.

But there's some really good news. You said that there were these studies where people doing lots of exercise in, like, their 70s or 80s and they managed to get their muscles back to a 20-year-old, which I love. You know, as I get older, I find all of those studies more and more positive. And you did also mention that women have a higher risk than men because they have less testosterone, so even more important there.

And then we talked about what you can do, and I think one of the most amazing things is this idea that you can eat a healthy diet, and that can actually help to support your muscles, and that we now understand that your microbiome is a really important part of this. And so sort of supporting the right bugs can affect your muscles partly directly and partly because it has this big impact on your inflammation and your immune system.

Protein is really important for your muscles, and so if you aren't getting enough protein, that is a problem. However, most people are in fact getting around 1.2 grams per kilogram just with the diet they're currently having. So this idea that we're all really short of it, and that is the biggest problem isn't really true.

And instead what you'd like to do is make sure you're eating a lot of foods that are high in protein, that are also good for your microbiome. And I heard beans, legumes, mushrooms, particularly dairy that's fermented, which, so like yogurts and cheeses, eggs, tofu, things like this. But you've got to have that still as part of a broader diet, and this is back to this Mediterranean diet that Claire, you were talking about and looking at this study.

So it's fitting in that also things that aren't high in protein but are just really supporting your microbiome. So whether that's olive oil, nuts and seeds, whole grains. All together, that is really shaping your microbiome. That's really supporting your muscle. And then last of all, I think most interestingly, what do you actually do?

So Tim says he now does a diverse set of exercises. You know, want to change every day. And Claire, I think really interesting, you've recently gone for proper intermittent fasting. You stop eating at 8:00 at night. You don't eat again until midday. You always have a very busy morning with three kids. You're a professor, all the rest of it.

At lunch, lots of, like, plants, you said, veg and salad and fruit. You do exercise in the morning in this fasted state, and actually you want to do more. And your guide was, well, if you're gonna do one thing, then squat while brushing your teeth.

Claire: Do something that's easy for you that you can incorporate. I think Tim's advice to do it in the morning is a really good one because it is the time when things are less complicated. Maybe we can inject a new good habit. And make it a habit is the way to go. Yeah.

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