Is it possible for somebody to have a lot of muscle, but their muscle health is poor? Yes. Okay. Conversely, can somebody have a moderate to low amount of muscle, but their muscle quality is high, or is that less common? Well, the first thing that you said is absolutely something that we see, is that in an individual that carries a lot of muscle and say they're inactive, there is a big discussion about how heavy individuals will have more muscle mass.

But what we have to recognize is the health of that skeletal muscle is fat deposition can be visceral fat deposition, fat around the organs, and it can be also fat infiltrate into the tissue, like, not to gross anyone out, a marbled steak. And that's exactly what can happen to unhealthy skeletal muscle, which then affects its ability to contract, which also affects, there's a ton of mitochondria in skeletal muscle, it affects the efficiency of skeletal muscle.

So yes, someone can have potentially more muscle, but more unhealthy muscle. Interesting. When you say a marbled steak, I think at the extreme, a wagyu, a raw wagyu looks like there's as much white fat in it as there is red meat in it. And it's a very different taste and texture.

So that's what we're talking about. My understanding is those cows don't move around much. They're somewhat sedentary compared to, say, a free-range grass-eating cow. Is that right? Yeah. Okay. That's absolutely correct. Okay. So we want quality, healthy muscle, and then we can talk about muscle amount. And then the other thing that I'll say about it is part of what defines muscle health is that flux, that movement.

So if you were to think about skeletal muscle like a suitcase, and an individual was, say, going on a trip for four days, but chooses to eat or pack for 30 days. We know these people. Yes, I know I'm maybe one of them. I have my suitcase here. I was only coming in for a day, but I may have packed for four days.

Not sure what I was doing, but that's besides the point. When an individual is overeating calories, overeating carbohydrates, I had mentioned earlier that skeletal muscle, one of its primary roles is glucose disposal. And I'm sure we're going to get in the mechanisms of glucose disposal, whether it's insulin-dependent or insulin-independent, depending on if someone is moving or contracting that muscle.

When an individual is eating food, carbohydrates, it gets stored in skeletal muscle as glycogen because, as we know, glucose at a high level is toxic to the body. So the body must move glucose out of the bloodstream into the cells. Now, what happens is there becomes this stasis. So if an individual is inactive and not exercising, then that skeletal muscle becomes overpacked.

Skeletal muscle at rest burns primarily free fatty acids, which is interesting. Most people think about skeletal muscle as burning carbohydrates, but actually at rest, skeletal muscle burns fatty acids. As you can imagine, when that muscle is full and you are not exercising it, then the substrates have nowhere to go.

And it remains in the bloodstream. And that would be a sign of unhealthy skeletal muscle, which then loops back to what you see in blood work. Elevated insulin, elevated blood glucose. Yes. Elevated free fatty acids, elevated branched chain amino acids, all of these things, which again, as skeletal muscle, as the metabolic sink, have nowhere to go.

So I'm starting to get a picture where in order to have healthy muscle, we need to think about the feeding of that muscle, the providing of nutrients to that muscle, that is, as well as the use of that muscle. Let's start with the feeding or the providing of nutrients to that muscle.

You mentioned that muscle at rest mainly burns fatty acids. It can store glycogen. How do we know when a muscle is full of glycogen? I mean, there's the visual representation of the muscle seems fuller as opposed to flatter, you know, but these are not specific or these are not precise terms.

You know, how much carbohydrate does it take to fill all the muscle of the body with glycogen? And then what sorts of things perhaps deplete that? I think it's a great question. We know that when we're talking about glycogen, the liver stores glycogen, maybe 100 grams. And then skeletal muscle, depending on your size, for example, you might store much more muscle glycogen, whether it's for 500 grams compared to someone who is my size.

And can we do the standard conversion of four calories per gram? So if the liver is 400 grams, you know, we just say, okay, there's about 1600 calories worth of energy there. So if I go out and I do some exercise and burn 1600 calories over time, does that mean that the liver is then completely depleted?

So, well, the liver will deplete through an overnight fast. So the liver maintains blood glucose. So skeletal muscle doesn't maintain blood glucose directly. The way that you would leverage muscle glycogen would be through exercise. The way in which you would deplete muscle glycogen would be through more intensive exercise.

And when you think about the foods and the way in which, you know, your original question is how would we know how much muscle glycogen or how much we need to refuel, I typically think about it as overall activity levels. So if someone is sedentary, then the current recommendation for carbohydrates would be 130 grams.

Per day? Per day. At four calories per gram? At four calories per gram. And is that both simple and complex carbohydrates, fibrous carbohydrates? Yes. It would just be overall. 130 grams. Yes. If they're completely sedentary. Yes. So just a little bit of walking, getting up, going to the computer, to the bathroom, to the car, et cetera, but basically sedentary.

Yes. And the average American takes in 300 grams of carbohydrates a day. So more than double. And as you can imagine, this can distort metabolism. When we think about glucose disposal, the way in which I think about glucose disposal, if an individual is sedentary, is thinking about how many carbohydrates an individual can ingest at one time that would mitigate insulin response and would be able to be disposed of safely.

And that number is between 40 and 50 grams of carbohydrates at a meal outside of exercise. The rest of carbohydrates would be earned through exercise. And through every hour of exercise, depending on the intensity, that could be between 40 to 70 grams, depending on how intense an individual exercise is.

And that would be safely disposed of in a two-hour period. I mean, when you think about an oral glucose tolerance test, that's a 75-gram load. You assume within two hours that that blood sugar regulation should come back to a normal range. So at 40 to 50 grams of carbohydrate every two hours, does that mean that if somebody were to eat 40 to 50 grams of carbohydrates every two hours?

Which they shouldn't. Which they shouldn't, right? But because you're going to quickly exceed that 130 grams per day. And even if exercising with resistance training, say, hard for an hour, which can afford somebody maybe, what, another couple hundred, 300 grams of carbohydrates? Probably not that much. Okay. You know, I think that if people care about body composition, which I would say everyone should, because you want to have an appropriate level of body fat and healthy skeletal muscle, then you wouldn't necessarily, unless you're doing some kind of cardiovascular activity, you're not using a ton of muscle glycogen, depending on how much you're training.

And how much glycogen is the brain using? So that is a good question. The brain uses a lot of carbohydrates. That would be a primary source. When they come up with the numbers of 130, it's really based on brain and then the rest of the body. Can we safely say that for somebody that's thinking a lot, they need more carbohydrates?

You could say that. Then your brain, yes, your brain is very metabolically active. Interesting. So we're kind of drawing rough estimates, not knowing people's body weight, not knowing their body composition. But what I'm arriving at here is, you know, if somebody does a little bit of cardiovascular training, maybe a little bit of light resistance training, I'm describing the activities of many people out there, maybe 250 grams of carbohydrates, you're kind of at the threshold.

That's a lot. That's a lot. Four calories per gram of those carbohydrates. So let's say 200 grams of carbohydrates per day. But that's not a ton of calories overall. So what should the remainder of the calories be made up of? So, you know, I think what we're really talking about here is how do we design a nutrition plan for people to have healthy skeletal muscle?

Right. And, you know, if I were to say, okay, what are we thinking about for the listener or for the people out there? They're thinking, you know, I really want to have a healthy body composition and healthy skeletal muscle mass. The way in which they would do that is, number one, you have to prioritize dietary protein.

So we're talking about carbohydrates here, but carbohydrates shouldn't be the primary focus. Nobody has challenges getting carbohydrates in. 130 grams would be a safe recommendation. If someone is overweight or struggles with type 2 diabetes or any of these other metabolic conditions, there is evidence to support a lower carbohydrate intake.

I mean, 130 grams is, you know, one little micro packet of pretzels on an airplane ride. You know? So that actually has probably closer to 37 grams of carbohydrates. Okay, good. Not that I had a pretzel packet before or threw one at Rob on the way in, but no.

Right. Okay, so I'm way off there. So they have one of those, a bagel in the morning, and they shouldn't, but they do. And then they have some, you know, pasta at dinner. And so most people are probably exceeding that 130 grams by a huge margin. Yes, they are.

And there's a couple things there that it's really important that you said is that individuals, when we're thinking about designing a plan for skeletal muscle health, that first meal is most important. That first meal of the day, having dietary protein will set you up metabolically for the rest of the day.

And when you say first meal, and we'll talk a little bit later about intermittent fasting and, you know, I, for instance, eat my first meal at usually 11 a.m. It's just kind of how I'm wired. I've never wanted to eat breakfast first thing. I've forced myself to eat some eggs first thing in the morning from time to time, and it felt fine.

But do you recommend that people eat a true breakfast, like within a certain number of hours of waking up for sake of muscle health and metabolic health? When we think about that first meal, I frankly don't care when you have it. One also has to understand that you're coming out of an overnight fast.

If you are young and healthy, then the timing of that first meal likely doesn't matter because you are robust, your body is very efficient and capable to withstand protein degradation. It's able to withstand protein degradation and protein turnover, which is ultimately why we're eating. So that's one reason why we're eating.

And we'll talk a little bit more about that. That first meal of the day, if you are young and healthy, the timing doesn't really matter. And I would say when it begins to matter is when you're older. When you are in your 60s, continuing to fast may be a negative, a negative for muscle health.

That first meal of the day is important because we know that when you get between 40 and 50 grams of protein, that first meal of the day, you stimulate muscle protein synthesis. Muscle protein synthesis is by proxy what we use to measure as a marker for overall muscle health.

Now, there's a lot of history here when we think about designing a meal plan. That first meal has between, we'll say, give it between 30 to 50 grams of dietary protein. That will do a number of things. Number one, it will stimulate skeletal muscle, what we would consider the health of skeletal muscle.

It also will affect the brain. It'll improve satiation. You and I were talking previously. It releases a handful of gut peptides. Like glucagon-like peptide one, which later we'll talk about. GLP, yes, GLP, CCK, PYY, things that will affect appetite for that second meal. There's some very interesting research out of Heather Leidy's lab.

Basically, when she put individuals, younger adolescents, on a meal of 30 to 40 grams of protein, they were much less likely to choose, say, donuts or something outside of what we would consider a healthy nutrition plan. Later in the day or in the same meal? Later in the day.

It was essentially augmenting their willpower. Okay, so it sounds like for young people, they can delay breakfast if they want. For older people, probably not. But that the first meal of the day should include what you're calling dietary protein, 30 to 50 grams. Yes. And maybe we should talk about the quality of that protein.

Because I think a lot of people understand that there are meat proteins, there are plant proteins. How important is the quality of that protein? This tends to be a hot topic and somewhat very controversial. Great. Great for you. I know. Great for everybody. I mean, controversy on this podcast is embraced in the following way.

We state what we know. We state what we don't know. And we are always happy to return to the conversation in a future time to adjust any stances based on the data and how we evolve as people. Okay. Well, I love that. Dietary protein, we speak about it as if it's one thing.

But actually, it's 20 different amino acids, nine of which are essential. The rest we can generate in our body. And when we think about skeletal muscle, we think about the essential amino acids. And the essential amino acids primarily for skeletal muscle health are the branch chain amino acids, leucine being one of those.

So leucine is uniquely stimulating to skeletal muscle. And when you have enough leucine, it triggers muscle protein synthesis. And when you say stimulating and muscle protein synthesis, I think a lot of people get a picture in their mind of a muscle growing. But you're not necessarily talking about that.

You're talking about the organ that is muscle, that its health, its metabolism being cultivated so that it can do all the hormone endocrine related things and the glucose disposal related things that we'll get into in a bit more detail later. Is that right? Yeah. And so when you have a breakfast of 30 to 50 grams, you appropriately stimulate muscle protein synthesis.

And one has to recognize that if you eat below that threshold, you do not stimulate the health of that skeletal muscle. You do not stimulate muscle in a way that would be necessary for outcomes that matter. And outcomes that matter are sarcopenia. Outcomes that matter are body composition, prevention of obesity.

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