Metabolism Myths Debunked: What Really Affects Your Weight?

Jim Hill: Welcome to Weight Loss And, where we delve into the world of weight loss. I'm Jim Hill.

Holly Wyatt: And I'm Holly Wyatt. We're both dedicated to helping you lose weight, keep it off, and living your best life while you're doing it.

Jim Hill: Indeed, we now realize successful weight loss combines the science and art of medicine, knowing what to do and why you will do it.

Holly Wyatt: Yes, the “And” allows us to talk about all the other stuff that makes your journey so much bigger, better, and exciting.

Jim Hill: Ready for the “And” factor?

Holly Wyatt: Let's dive in.

Jim Hill: Here we go.

Jim Hill: Welcome to another episode of Weight Loss And… Holly, today we're going to talk about metabolism.

Holly Wyatt: That's a loaded word, but everybody wants to talk about metabolism. That's common.

Jim Hill: I know a lot of people come in, and they're convinced their metabolism is broken. That's why they've gained weight. We're going to dive into that today. Metabolism is a complicated issue. We will simplify and provide practical information about your metabolism. Why do people care about this, Holly?

Holly Wyatt: I think they think that they struggle with their weight loss. One of the things they've been told and they think about is that they blame it on their metabolism. Or there's something wrong with their metabolism and they want to fix it. I think that's why they're interested in the subject. It could be a reason why they struggle with weight gain or can't lose weight. A lot of people have talked about it. It's my metabolism. They're very interested in it.

Jim Hill: So let's dive in. When we talk about metabolism, your body's metabolism is the result of all the chemical reactions in your body. You take in energy in the form of food and you expend energy through all the body's processes. If you're gaining weight, you're taking in more energy than you're expending. If you're losing weight, you're expending more energy than you're taking in. If you're not eating a lot, then maybe you have a low metabolism.

So let's look at what science tells us. If you're at rest, you're not eating and you're not exercising, that's called your resting metabolic rate. That's the amount of energy your body uses in a resting state.

Holly Wyatt: I like to describe it as if you're laying in a bed, you're not asleep, but you're not moving a muscle. You're not doing anything but being completely still. Your resting metabolic rate is the amount of calories it takes just to keep your body alive, to keep your heart pumping, your kidneys going, and your muscles alive. It's just like the bare bones. That's how much energy it takes to keep your body alive.

Jim Hill: One of the questions that a lot of scientists have asked over the years is, does a low resting metabolic rate cause weight gain? In many studies, what we find is your resting metabolic rate, the number of calories you're burning at rest, is most related to your body size and body composition. If I measure your body composition, how much muscle, and how much lean mass you have, I can very accurately predict your resting metabolic rate. People who are overweight, Holly, have a higher, not a lower, resting metabolic rate. There's some variation, so there's normal variation, but in general, your resting metabolic rate is very much tied to your body size.

Holly Wyatt: That's one of the myths that's out there. I think people think if they are overweight, then their metabolism is low. And actually, we find the opposite. The more muscle you have, the more fat you have, the bigger, the more you weigh, the higher your resting metabolic rate, not the lower. It's the opposite, I think, of what most people think. As you gain weight, your RMR, your resting metabolic rate, actually goes up, not down.

Jim Hill: And when you lose weight, your resting metabolic rate goes down. That's another topic that we're going to take on is how your metabolism changes with weight loss. But for today, we're looking at a broken metabolism as a cause of weight gain. So it looks like RMR is not a major player here.

There are other aspects. When you eat a meal or you consume food, it takes some energy to process that food. It's generally eight to 10% of the energy in your meal.

And what we've seen over again over many, many studies is doesn't seem to be big differences there in people. That's called the thermic-effective food. And again, it doesn't look like a low thermic effective food is the cause of weight gain or a major cause of weight gain. The final one, Holly, is physical activity. This is the most interesting one because depending on how much physical activity you do, that can be a very low part of your daily energy expenditure or a very high part. So it's the most variable form of energy expenditure.

Holly Wyatt: Right. And so it's the one you have the most control over really in that you can decide how much you're going to move. And that can have an impact on how many calories you burn or your total metabolic rate. I think one thing to just make clear here, is metabolism, which we're talking about in terms of energy metabolism. And like you've talked about, some people talk about carbohydrate metabolism or protein metabolism.

There's so much out there. But when we think about body weight and weight loss and weight gain, we think about it in terms of energy, in terms of calories, and physical activity. How much you move your body is what you control the most. The rest of that, the other piece, the RMR, and the thermic effective food, that's kind of set. You don't have as much control over that.

Jim Hill: So if we look at total energy expenditure, we can look at resting metabolic rate, thermic effective food, and the energy expended in physical activity. And of those three, it's the energy expended in physical activity. That's the most variable. The other two are pretty much set by your body size. So is your metabolism broken? In terms of a low energy expenditure, I think we can conclude not really.

Holly Wyatt: There's some variability. And that's what I think people would argue. Well, we can predict your resting metabolic rate based on your body composition, how much muscle, and how much fat, and we can predict it. But there is still a little bit of variability and you may be in the low end. Here's the normal range and you're in the low end. And does that predict weight gain? And there have been studies that looked at that saying, if I'm on the low end of what you would think I should be, not abnormal, but the low end, does that predict that I am going to gain weight in the future? And I think those studies have been done and it is not a good predictor.

We thought it would be. I think a lot of people said, “If you're in that low end, it should make a difference.” But it doesn't. And I don't know exactly why, except there must be other things. I always think other things may be more important than kind of lunt that effect.

Because you would think if you're burning fewer calories because you're at that low end of normal, then that might set you up to gain more weight. What do you think about that?

Jim Hill: Well, I agree. I think despite people believing that they eat very little food and yet they're overweight, when we study people very carefully, we find that that's not the case. We've not been able to find any of these people who say, I eat almost nothing and I'm overweight. If you're overweight, your energy expenditure is higher. And to maintain that state, you have to be eating more. Part of the problem with food intake is it's very, very difficult to know how many calories you're taking in.

People get it wrong. You feel like I'm not eating very much. But when we study people, we don't find that. So I would say that in terms of low energy expenditure, it's not a cause of weight gain in the majority of people.

Holly Wyatt: I tell my patients that this is a good thing. They almost want there to be something wrong with their metabolism because they're struggling. And if they can figure out what it is, can I fix it? They come to me, do I have my metabolism broken and can you fix it?

It's usually the follow-up question to that. And the good news is we don't need to fix it. It's not broken in this sense at least. And so this is a good thing because you wouldn't want that to be the case if you couldn't do much about it. So this to me is a good thing, not a bad thing that you're not set up, that you can overpower it. Having a low resting metabolic rate doesn't mean you will gain weight or can't lose weight. Seem to be a great predictor of that.

Jim Hill: So what do you tell people that come in and they're convinced? Holly, I just know I don't eat very much. It has to be my metabolism.

Holly Wyatt: And I first off say, when they say that to me, I'm not going to necessarily say you're wrong because they are not in the right frame of mind. They want their struggling, right?

They want me to listen to them. I think they are struggling and other aspects of their metabolism may also be affecting them. I'm going to check things and make sure that their thyroid is normal, usually not the problem. But I'm going to look at all that and we're going to start talking about it. But it's not about the resting metabolic rate. However, there are other things that we can talk about.

So we start opening that dialogue. To me, when someone says, my metabolism is broken or I don't eat a lot, it is a sign that they're trying hard. And we know that certain people do struggle more. It's just not that resting metabolic rate piece that I think is the big player.

Jim Hill: I've noticed a lot of products in the advertising world that claim to enhance metabolism, Holly. Even though your metabolism isn't broken, is it possible to boost it up? Can we make our metabolism higher, which would be a good thing in terms of managing weight?

Holly Wyatt: So there are lots of supplements that talk about boosting metabolism or fat burners. When you look at those in the studies, if they have an effect, there are a few things that may have a little bit of an effect. I know there's some caffeine and green tea and some cayenne pepper. Some small studies show small increases, but not big ones.

Not big, not really. I'm not saying it doesn't have any effect, but I don't think it has a significant effect. I think there are other things you can do that have a much, much larger effect. And like I said, the studies don't support big increases at all in terms of energy metabolism. In the past, when we've had some medications that have done that, or if you were on thyroid hormone at too high a level, it could do that.

And it's dangerous. It has side effects that occur when you boost that metabolism up. Some drugs can boost your metabolism, but they can also have harmful effects on your body, so we avoid using them. So the stuff that is available as the supplements, in my opinion, just don't have a lot of strong data that they're doing very much. If anything, it's a small, small amount.

Jim Hill: Holly, but there is one thing that people can do to increase their energy expenditure or their metabolism. And, this is one of my favorite topics to talk about, and that's physical activity.

Holly Wyatt: Right. Moving. You can control that. And you can increase the total number of calories you burn way more than any supplement. And there are so many other positive things. But for some reason, that does not seem to be the thing people want to talk about the most. But you're right. It can have the biggest effect on your energy metabolism and I think your body state.

Jim Hill: So again, looking at our components of energy expenditure, resting metabolic rate and thermic effect of food is pretty much set by your body size. This collectivity isn't. And in that sense, it's the most variable part of energy expenditure. And if you're one of these people who never get off the couch, you're very, very inactive, then your energy expenditure is at the low end, which means you can't eat very much food or you're going to gain weight. If you're a physical activity at the high end, and I love some of the studies that are done in elite athletes, and I know that not everybody can be an elite athlete, but these people that are very, very active, they can pretty much eat anything they want without gaining weight. So if you think about it, increasing your level of physical activity at one level means you can eat more without gaining weight.

Holly Wyatt: Right. So it's in that spectrum. And I think we've, as a society, moved way down to this kind of low metabolism because we're not moving, not because our resting metabolic rate is low, but because we're not moving.

And maybe things don't work right. And so, when I started, I studied resting metabolic rate. Remember, that was one of my very first studies, Jim. I measured resting metabolic rate in people who had never lost weight, and I measured in people who had lost weight. And so I, this was one of my favorite topics, and didn't find much there. And therefore, I always said, no, your metabolism is not broken.

It's appropriate. But now, when we get to this physical activity piece, what do you think about, would the metabolism be broken when we think about how much movement they're doing?

Jim Hill: I think this is very important. So much focus is on food intake, Holly, in obesity. And clearly, food intake plays a role. But we as a society have become so sedentary.

And I think our bodies are meant to move, and I think they work best when we're moving. And so I think that inactivity feeds back on your metabolism in many ways. Number one, it makes your total energy expenditure lower. But as we're studying this, we find so many other things that physiognomy can do. Interestingly enough, it helps regulate your appetite a little bit more.

It may increase your ability to burn the fuels that come in rather than store them. And we're going to hit physical activity over and over and over. But the reason is I'm convinced that for most people, there are exceptions to everything. But for most people, increasing physical activity is essential if you want to maintain a normal, healthy body weight.

Holly Wyatt: I agree. And to me, that's the broken part, right? That's right. What you should be focusing on is this. It's not just about burning more calories. I think when I talk to people, they're like, OK, so I can go out for a walk and I'm going to burn 300 calories.

But big deal, Holly. I'm like, yes, you're going to burn 300 calories, and that's good. And we think it does more than just that. It's not just about the calories you burn. It's also, I think, helping your metabolism adjust to what you eat. And as you talked about, perhaps helping the hormones even that control appetite so that you tend to balance, meaning how many calories you're eating tends to balance, how many calories you're burning, and you don't gain weight, right? You're not in that positive energy balance. So to me, it's not just about the calories, but there's so much more to unpack with this that, to me, it's like the most powerful piece when we look at metabolism. Yes.

Jim Hill: And I know it's difficult if you haven't exercised, perhaps for years and years and years. It's tough to get started. And one of the things that we know is if you're sedentary and you start exercising, it doesn't feel good right away.

You need to work through it a little bit. And we're big fans of starting slowly. And people always ask me, what's the best way to start exercising? And overall, I think one of the very best ways is to start walking more.

Holly Wyatt: I agree with that. And we don't know how much physical activity it takes to get you in this better metabolic state that we're talking about. And, Jim, I want us to start talking about the term metabolic flexibility because it is a term I want our listeners to understand. It's a good one.

I mean, I know it's in the science world, but I think our listeners can grasp this. And I want them to start thinking about how flexible is my metabolism. What is my metabolic flexibility? How do you describe metabolic flexibility?

Jim Hill: So that's very different than energy expenditure. We're sort of going in a different direction here. So during the day to eat food, you eat a combination of protein, fat, and carbohydrate.

Right? So your metabolism and the fuels you burn are constantly changing. So the longer you go between meals, the more your body burns fat and not carbohydrates.

Once you start eating food, that body switches and starts burning carbohydrates and decreasing fat burning. So during the day, your body is constantly switching between the kinds of fuels it uses. The concept of metabolic flexibility is someone who's highly metabolically flexible is better able to switch quickly to those fuels than someone who isn't.

And what we think is that over time, that slowness in switching can contribute to weight gain. It's a little bit, Holly, one of the sort of analogies is the thermostat. If you have a really good thermostat, boom, you crank it up. The temperature comes up quickly.

Another one, you crank it up. It may take, to get there, but it may take a while. And this slowness in changing between fuel sources over time might contribute to contributing to a little more positive energy balance. And one of the things we know is the best way to increase metabolic flexibility is physical activity.

Holly Wyatt: I love the term metabolic flexibility because I can envision it. You're flexible, so you eat a little bit more dessert. Your body can handle it. It's not that you lose weight or it's that you just stay the same, that you balance, that you're flexible. You take in and you deal with the calories that come in, whether they're carbohydrate or protein or fat or whatever.

And then the calories from an energy standpoint. And to me, it's like, how flexible are you? I would love for us to be focused not on what's your resting metabolic rate because, to me, that's set. I would love to instead, my patients be focused on what's my metabolic flexibility. How flexible am I? And in a state of slim, we have a number.

We work on it. Are you 20% flexible, 30% flexible, 40% flexible? This means how many additional calories can you take in, and your body burn without gaining weight or regaining weight? To me, a broken metabolism is an inflexible or tight metabolism that can't adjust when you want to have a piece of cake. You want to go out and have some pizza.

Jim Hill: It's a different way of thinking about metabolism. And so on metabolic flexibility, you might not see it all the time. What you have is a metabolism, it's ready to go. If excess comes in or if changes come, your metabolism, it's like a car that's already revved up and ready to go. And if you're metabolically inflexible, you have to start it and get going and it takes longer. So you don't respond to those excess calories quite the same way.

Holly Wyatt: And the idea is you don't respond and you may tend to store them. To gain weight or regain weight. And so you store them and that's it. But to me, this is the sexy part of metabolism because this is the exciting part of metabolism. And it's what you can do with movement and we can all control that.

So I would much rather have my patients come in and say, “Your metabolism may not be very flexible. You tend to gain weight easily or you tend to regain weight easily.” And that's what they're saying. Let's work on getting your metabolism flexible. That to me is the exciting piece.

Jim Hill: One of the things I think we know is that if you lose weight, that can help your metabolic flexibility a little bit. But the way you boost it is by increasing your physical activity.

Holly Wyatt: I even think sometimes weight loss may make it worse. I think you have to be careful. Metabolic flexibility is not about weight loss. It's about preventing weight gain and preventing weight regain and getting in that balance. The calories coming in and the macronutrients coming in are balancing what I'm burning. And my body is helping me do that.

That's giving me that extra piece. And so being more physically active allows my body to do that more. And I think some of us do it better than others. I think people who don't struggle with their weight, I think they're very flexible and they may be flexible, have a flexible metabolism without doing a lot of exercise.

Jim Hill: But there's a genetic component to all this, everything. And if you're genetically fortunate, you probably have high flexibility without working for it.

Holly Wyatt: But most of us have to work for it. I have to work for it. Yes. And I was born inflexible, I decided. So the good news is I can work on that. That's what I love about this.

Jim Hill: And so personally, what's your physical activity plan, Holly? How do you incorporate physical activity?

Holly Wyatt: So I know how much activity I need. I've done this for so long. I know how much physical activity I typically need to be able to be flexible and to eat extra calories, to go out and have that pizza and whatever I want. Not whatever I want to have extra calories and take care of it. So for me, it is about an hour's worth of movement a day added to a pretty active lifestyle. So I need that and I can get up to about a 40% flexibility range. And what I mean by that is that I can eat about 40% of my meals kind of off plan and then 60% of my meals are pretty controlled. But 40% of my meals are not controlled. That's pretty good. That's great for me.

Jim Hill: Oh my God. So one of the things that is important about what you said is you do planned activity, but you also look at being more active during your day. Okay. Putting physical activity here, walking a little bit more, getting up and moving around. So there's both planned activity and there's the activity of daily living.

And I think it's important to try to increase both. But don't start, if you have an exercise, don't start in an hour or a day. Takes a while. Start by just walking a little bit more. Everybody, your phone measures your walking. You can get a pedometer, all kinds of however tech-savvy you are. You can get devices that measure your walking and just start walking a little bit more each day and work your way up.

Holly Wyatt: Some studies show that just going from sedentary to a little bit of activity has a big bang for your buck. And I do think that allows more of that flexibility.

And so you don't necessarily have to push it up as high as I do. But just to get started, I think can be helpful. And the message I want people to understand is I think it's more helpful than just the calories you burn. Sometimes they look and say, oh my gosh, if I'm just going to walk for 15 minutes or I'm going to do something 2,000 steps today, the amount of calories that burn is so small. I'm like, oh, it's not just about the calories.

Jim Hill: And it's another myth that if you exercise more, you just eat more. That isn't the case. And, if you exercise more, you regulate your appetite. So it's better matched to your energy expenditure.

That's that metabolic flexibility. We'll talk some more about physical activity. Being physically active is crucial for weight loss and maintaining weight.

So the take-home message is if you're not active, you need to start. And again, when it comes to physical activity, more is better. So if you're doing nothing, doing a little bit is better. Doing a lot is better still. But being sedentary, I think is one of the greatest risks for weight gain that we know of.

Holly Wyatt: If you're convinced that your metabolism is broken, you might be right. And the way you can fix it, and this is the good part, the way you can fix it is to start moving more, and you can do it slowly and ramp up. That can fix what I think people think about when they say, I have a broken metabolism.

Jim Hill: So some good stuff here in this episode. But the message is if you think about the number of calories you expend, your basic metabolism isn't broken. It's determined by your body size. The more you weigh, the higher you're resting metabolic radius. But the variable piece is physical activity. It burns calories, but that may not be the most important thing. It may increase your body's ability to adjust to changes in food intake.

Holly Wyatt: All right, Jim, I think we covered it a lot more.

Jim Hill: Oh, that was a tough one. Explaining metabolism can be challenging, but people must grasp that they shouldn't attribute all of their problems to metabolism alone. There are things you can do to prepare your metabolism for the real world and manage your food intake and eating habits.

Holly Wyatt: And it may be certain people. We're not saying that physiology isn't involved. We're just saying, think of it a little bit differently. It may be that you do have a metabolism or physiology that's going to require a little bit more activity. But the good news is you control that.

Jim Hill: Thanks for tuning in to this episode. I hope you learned a little bit about metabolism, and we will see you next time. Thanks, everybody.

Holly Wyatt: See you soon, guys. Bye.

Jim Hill: And that's a wrap for today's episode of Weight Loss And ... We hope you enjoy diving into the world of weight loss with us.

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Holly Wyatt: And remember, the journey doesn't end here. Keep applying the knowledge and strategies you've learned and embrace the power of the “Ands” in your own weight loss journey.