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So here's an interesting question, Rhonda. So we know the rates at which muscle mass, skeletal mass um are declining by decade in an aging population. Um is there any way we can estimate? I'm guessing the answer is no, but on the off chance you would know. Is there any way we can estimate what percent of that decay is simply being driven by uh insufficient amino acid consumption versus other factors? Right? Other factors would be anabolic resistance associated with aging. Other factors would be anabolic resistance associated with sedentary behavior. Other factors would be lack of sufficient resistance training. Like there are many factors that explain clearly the fact that as a person goes from 50 to 60 to 70 on average, they're losing muscle mass. But it would be interesting to consider how much of that is explained by the fact that they are also barely skirting the minimum amount of nitrogen that they need and in many cases falling below it.
Right. I so to answer your question, I don't know that there's a direct way to do that, but I do know that there are studies that have shown that when older adults, so older adults like that are really more suscept susceptible to the things that you were saying like anabolic resistance um where people are basic where your muscle tissue is not as sensitive to amino acids because of mostly because of phys physical inactivity which increases with age. Um but when older adults take in 1.2 grams per kilogram body weight per day of protein, it it nearly eliminates um some of the age related muscle loss that happens. So I think that is some evidence to sort of support what you were saying in that if you just increase your protein intake to 50% yeah by 50% to this minimum what the RDA should be 1.2 grams per kilogram body weight per day. I think that's pretty much what most all the experts agree is that like it's time to change that RDA to that number right? The minimal amount that you need per day. If we just do if older adults just do that, they're they're actually preventing a lot of the age related loss in muscle that occurs. And we also know that um older women, if they take in that amount of 1.2 grams per kilogram body weight per day, they're 30% less likely to have frailty in old age, which is also very important, right? So, I think that's pretty good evidence that it's clear that just increasing your protein intake by 50% is really important for aging, right? For our muscle, for our muscle health and also is getting us out of that net negative state that we're in.
So I mean I know >> so so step one is we should move the floor from 0.8 to 1.2. >> Yes. I think the floor being the minimal amount of protein that we need to take in per day. This is not optimal. We're going to get into optimal, right? This is just like the new RDA, right? And and as you mentioned, so you kind of hit on this anabolic resistance, and I think that's also a really really important point because it does compound with the fact that we're already not getting enough protein to to to to be in a a positive state of protein balance. And then you compound that with anabolic resistance, right? Now, anabolic resistance is when your muscle tissue becomes less sensitive to amino acids, and so you're not making as much muscle protein synthesis isn't occurring as much as it does when you're younger. I think it's pretty consensus now that a lot of anabolic resistance is not necessarily aging. The aging process per se, so much as >> inactivity. >> Inactivity. >> Yeah. And the experiment that Luke von shared when he was on the podcast I think was a very elegant way to do this, which is um they took uh young subjects. I don't remember if they were in their 20s but it was thereabouts, maybe in their 30s, so very young subjects, and they put a cast on one leg, no cast on the other, and they left them in this state for a period of time. Again, the details have now completely escaped me, but the the point is has not escaped me, which is after whatever period of time the individuals were casted on one leg, not casted on the other, let's just say it was two weeks, four weeks, something to that effect. They removed the cast. Uh, of course, while the person was casted, the casted leg did nothing. The other leg continued to go through exercises. They were doing a bunch of single leg, you know, leg extensions, leg curls, things like that. They then ran the stable isotope experiment in these individuals and looked at muscle protein synthesis rates. And lo and behold, the individual, the leg that was unccasted, perfectly normal. The other one, significant anabolic resistance. So to me, that's the clearest demonstration that inactivity is the main culprit. There's probably an all things equal age related component as well. Um, but I suspect that inactivity is playing a larger role than aging per se.
>> I totally agreed. Um yeah, I think there was there's also another study that was done in older adults. So first of all, if we if we look at >> maybe we should talk about >> can we explain what anabolic resistance is? It's I think it's worth people understanding why this idea matters. >> Yeah. Anabolic resistance. So So our when we eat protein, right? We we're breaking down amino acids and you know, the primary amino acid that is that is anabolic is leucine, right? So these amino acids like leucine are getting into the muscle tissue and that is instigating it's a signal to increase muscle protein synthesis. Right? So you're making more mus you're making more protein in your muscle and that in in turn increases muscle hypertrophy. Right. Um the other major major signal to do that is mechanical force. Right. So that would be the resistance training, the work of the muscles. So as we get older, our our muscles do become less sensitive to those amino acids, like the leucine transporter being one of the major ways, but I think there's others as well. And so what happens is is that for the same amount protein dose, and this study has been done, and if you compare younger adults and older adults, 65 years age and older, you give them the same exact protein dose. The older adults are have like so I guess let me say it the other way. The younger adults have twice as much y >> um muscle protein synthesis. And for the older adults to get the same amount of muscle protein synthesis, they had to double their amount of protein to get the same amount of muscle protein synthesis as the younger adults. That's a lot. They had to double that amount of protein. Okay? So, um and that's because again, you need it's just your your muscle tissue is not as sensitive to the amino acids and so to get more of them in, you have to increase your intake of the protein. Um, now to your point about physical activity being the major driver here, it's I think that's 100% I agree. I think it's totally true and there's so much evidence out there to to prove that Luke Vanlon's study being one. But also, older adults that do engage in resistance training have the same anabolic response to the same amount of protein as younger adults. So, in other words, >> the activity makes up for it. >> It does. You don't have to as you're aging, as you be, if you're a 65, 70-year-old male listening to this episode and you're engaging resistance training, you're likely not experiencing much anabolic resistance. Maybe a little, but not much. And so, you don't necessarily have to experience it if you are physically active and training. And that's really the bottom line here. That's the most important thing. If there's a public health health message, you know, in this episode, it really is you should be training.
>> Yeah. And think about the impact that physical training has on insulin resistance as well. Completely different mechanism of action. Uh probably ties in more to, you know, uh fatty acid accumulation within muscles and all sorts of other things that lead to it. But again, the most effective remedy is physical activity. Um and again, this is Yeah, I mean, it's just it's been demonstrated so conclusively that actually nobody really talks about it. It's just taken for granted. >> No, it's a good point. Um but you know so so the anabolic resistance if we're if we're if we're talking about like general population and again we're going back to these surveys that are done looking at how physically active are people because those numbers are out there right? We know that generally speaking adults, including young and old adults, about 32% of them engage in resistance training. >> How much? >> 32%. Both young and old. >> If you just look at older adults, it's 22% of the population. So essentially, most older adults, most people are not engaging in resistance training. They're not they're not doing resistance training, right? Um and physical physical activity kind of mirrors a little bit those numbers. But I think the bottom line here is that most people putting in the effort, it's harder for people. Putting in the effort is harder. It's easier for them to just increase putting something in their mouth. That's why pills are so popular, right? I mean, people always kind of gravitate towards the easier thing to do, which is like, I'm going to eat something. I'm going to put something in my mouth versus like putting in the effort. It's unfortunate, but it's like it's a reality. And so, I think that even just going back to this RDA being too low, it's just so important. It's so important because people are out there thinking they're getting enough protein, older adults, younger adults. It's really more important with older adults. You have a little bit of wiggle room when you're younger, right? But I mean, and then on top of that, first of all, it's not enough protein. And then this anabolic resistance is setting in. And most people are not being active. They're not engaging in resistance training. So there's all these compounding factors that's really just digging into their muscle. It's taking away this like insidious sort of taking away each year, each year, and then the next thing you know, you're frail, you have sarcopenia, you know.
>> Yeah. I I I my patients are obviously um indoctrinated into this, but I'm a bit surprised that there aren't more people that talk about this. You do a lot. Um but the the medical system doesn't seem to talk enough about frailty and sarcopenia. Um and and I worry that even when I wrote Outlive, I didn't do enough of a job emphasizing it. I mean, I certainly talked about it, but when I talked about four horsemen, I talked about cardiovascular and cerebrovascular disease, cancer, neurodegenerative and dementing diseases, and metabolic disease because of course, those are the things that are the main assault on your lifespan. Um and relative to those, frailty is not as big as as big an assault on lifespan. It is, as you know, the risk of falls are enormous and the mortality is very high once you're north of 75. But relative to those four, it's, you know, I had to pick four horsemen. I didn't want to go with five. But when you think about quality of life, which most people care about at least as much, if not slightly more than length of life, I think frailty just kind of wins the day. Um I I think along with cognitive health, right, and and minimizing too much cognitive decline, frailty is the thing that seems to determine the quality of your final decade on this earth. And here we have lots of great tools, both in terms of training and nutrition, that can offset that. Um and yet it is surprising that that despite the fact that most people have witnessed it, that's the part that's amazing to me. It's not like the people who are suffering from frailty and sarcopenia are out of sight because they're our parents and our grandparents. We've watched it. We've been to the movie over and over and over again. We see how it goes. And yet somehow we either don't think it's going to happen to us or it somehow still seems abstract because it's so many years off. I mean, what's your take on this overall challenge?
I I mean well for one, I think that I I completely agree with the frailty risk being as important if not more. And you know, witnessing it with like family members, you know, it's it I what what I think it is, is that it's like this incremental thing, right? Where something happens to like maybe there's a fall, or maybe there's just a surgery, a planned surgery, or a hip replacement or a knee replacement, and pe and your your parents or your grandparents are inactive for many weeks and they lose a lot of muscle mass, right? So, they this this happens when you're young. If this is if this is a younger person, it's much easier to gain back that muscle mass, right? It's not the same with an older adult. It's just not the same. Even if you're engaging in resistance training after, it's you're not going to get the same amount of muscle mass back as you've lost. And these sorts of events um kind of happen like in periods of time, right? World like there's a planned surgery, then there's a fall, and maybe there's another surgery or maybe there's an the COVID or the flu or whatever it is, they keep hitting, right? And you you reach this sort of what's called disability threshold where all of a sudden your parents like they just can't walk much at all anymore. And it's like all of a sudden it's like when did this happen? Well, the evidence was like mounting over the last five years when they had these points of inactivity that that were occurring. And so I think people kind of just don't follow the timeline, you know, where it's like they see what's leading up to it and before this sort of catabolic crisis occurs where then they reach this point now where they've just lost so much muscle mass from these several events that have occurred where they're just not mobile and then of course anabolic resistance is kicking in even more and more and more and everything is just compounding. And I don't think they've like they've like observed the timeline and said, "Oh, A plus B plus C is getting me to this point."