I’ve been doing a lot of research lately on human metabolism and I’ve noticed a lot of inconsistencies in the data available. There seem to be a lot of misconceptions about metabolism, especially …
My name is Patrick McGilvray, and I’m an experienced marathoner, ultra runner, Sports Nutritionist, Master Life Coach, and weight loss coach for runners. I’ve dedicated my life to helping runners just like you properly fuel your body and your mind. So you can get leaner, get stronger, run faster, and run longer than you ever thought possible. This is Running Lean.
Hey there, and welcome to episode 186 of Running Lean. My name is Patrick McGilvray, The Weight Loss Coach for Runners and today, Demystifying Metabolism. So I’ve been doing a lot of research lately on human metabolism.
And I’ve noticed a lot of inconsistencies in the data that’s available out there. There seem to be a lot of misconceptions about metabolism, especially when it comes to you know people who want to lose weight.
So today, I want to take some time to address some of the most common myths and misconceptions around human metabolism. I did an entire episode on Fixing Your Metabolism that was Episode 141. So you can definitely check that one out.
I won’t be rehashing all of that here today. Today, I’m going to focus on demystifying metabolism. So you can separate fact from fiction and make better choices to improve your overall health and fitness.
But first, if you’re anything like most runners, you’re probably really good at being an endurance badass. You’re amazing at getting out there pounding out the miles on the roads or on the trails. But when it comes to being strong, if you’re like most runners, you probably fall a little bit short.
Building and maintaining strength is essential to improving your running performance and your overall health and hitting your weight loss goals. But most runners just don’t do it or they just don’t do it well.
So building strength is probably the second biggest driver when it comes to improving your body composition after nutrition. So if you want to lose fat and gain muscle, you have to be doing some sort of resistance training regularly because lean runners are strong runners.
So some of the benefits that you will experience, if you participate in some sort of regular resistance training, you’ll lose more weight and faster, you’ll be at a much lower risk of injury from running, your endurance will improve, you can actually run longer before you get fatigued, you will run faster, your power to weight ratio goes up making you a more powerful runner.
And evidence has shown that you actually live longer. People that do regular strength training tend to live longer than those who don’t. So it’s one of the best things you can do for your overall health and fitness and to change your body composition is to get stronger. Regular strength training will help you burn more fat and gain lean muscle the more weight you lose, you’ll run more injury free you’ll be able to run longer and run faster and live longer.
All these things are amazing. If you want to learn exactly how to become a stronger, faster, leaner runner, join the Running Lean Coaching Project. That is my unique weight loss coaching program for runners. Just go to runningleancoaching.com/join to learn more about that.
And if you just want a little help getting started with all this stuff, I’ve got this great training program that I put together, you can watch it for free, it’s called Five Simple Steps To Becoming A Leaner Stronger Runner. Just go to runningleancoaching.com and click on Free Training to get started.
Alright, let’s talk about demystifying metabolism. So I want to start with what is metabolism? So metabolism is a term that describes all the chemical reactions in your body that keep your body alive and functioning.
It’s also responsible for converting nutrients from the foods that you eat into fuel. So this provides your body with the energy it needs to breathe and move, digest foods, circulate blood, repair damaged tissues and cells and so much more.
So the faster your metabolism is, the more calories your body tends to need. Metabolism is the reason why some people can eat a lot without gaining weight while others seem to need less to accumulate fat. The speed of your metabolism is commonly known as your metabolic rate or resting metabolic rate.
It’s the number of calories you burn in a given amount of time, okay, and some people talk about it as calorie expenditure. So, the first myth I kind of want to address here is that metabolism is not just about calories. So many people consider metabolism only under the scope of calories and weight.
And you know, for the most part we are talking about that, but you have to understand that metabolism encompasses all chemical reactions in the body, from absorption of light to the creation of usable ATP energy to body temperature regulation to hormone production to balance of fluids and hydration in the body to your circadian rhythm and so much more.
So if it’s a function of the body, it’s likely to be related to metabolism in some way or another. Okay, so just understand that metabolism is about a lot more than just burning calories.
Okay, the next myth I wanted to address is that eating more often will increase your metabolism. So eating small, frequent meals throughout the day will help boost your metabolism. And the idea is pretty simple. Because whenever we eat food, our body does burn some calories to break the food down to absorb the nutrients. This is called the thermic effect of food.
So if we are constantly eating, wouldn’t our bodies constantly be burning calories? It just doesn’t quite work that way. Okay, so eating small meals throughout the day may help you with portion control, but it doesn’t really speed up your metabolism.
Researchers have studied people eating six meals a day compared to people eating three meals a day, and they found that there really wasn’t any difference in a 24 hour fat oxidation rate. So this is one measure of metabolism, okay.
They actually found that people that eat more often throughout the day, have increased feelings of hunger and tend to eat more in general, okay. So understand that there is a temporary boost in your metabolic rate when you’re eating food, all right.
But eating six small meals over the course of a day isn’t really going to cause any kind of overall increase in your metabolism. In fact, it’s going to probably cause you more hunger, and cause you to eat more food overall. Okay, so eating more often does not increase your metabolism.
Another big myth that a lot of people adhere to is that your metabolism slows down as you get older. And this is sort of true, but I want to break this down, so you fully understand what this means. Okay, so a lot of people will just say, well, I’m older, and so my metabolism has slowed down.
And you can pick any age, and people will tell me this, because I talk to people all the time in their 40s 50s 60s 70s, whatever. And they just tell me, oh, yeah, my metabolism, my metabolism has slowed down. So I tend to put on more weight.
Okay, so they’ve done some studies recently in like 2021. And they’ve shown that this is not really the case, okay. So the rate at which your body burns energy, your metabolism is thought to decline during middle age as people gradually lose muscle mass, okay.
So they did a study where they looked at total energy expenditure, including energy burned at rest, to perform basic functions like digesting food as well as energy burned during physical activity. And they looked at like 6400 people ranging in age from eight days old to 95 years old, okay, they looked at their height, their weight, their body fat percentage. So they calculated average metabolic rates for men, women and different people in different age groups.
And the data indicated that there were some differences in metabolism based on four distinct periods in people’s lives. So the first is from infancy to one year old, this is where your metabolic rate surge is, okay? It was about 50% higher than it will be during adulthood.
So this is a huge surge in your metabolism, which makes sense. You’ve just been born, you got to, you know, grow bones and get a big brain and all these things, your metabolism is super high during that first year of life, okay. Then, from age one to age 20, this is like the second period that we’re talking about here. Your metabolism decreases by about 3% a year. Okay, so your metabolism is actually decreasing from one until you hit age 20.
But then, from age 20 to age 60, they’ve shown that your metabolism really doesn’t change. It stays pretty consistent. Okay. After age 60, and this is the fourth period, metabolism decreases by 0.7% annually, which is not insignificant, but it’s not as much as people think. Okay.
So infancy to one year old, your metabolism is surging, it’s about 50% higher than it will be during adulthood from one to 20 when it decreases by about 3% a year. From 20 to 60 doesn’t change. And then after 60, it decreases by around 0.7% annually.
And something interesting about this is that there are ways to actually prevent that deep annual decrease after age 60. And it’s more likely changes in lifestyle, like eating the proper diet, staying active and maintaining lean muscle mass all have positive effects on your metabolism after age 60.
So even though the data is saying like, oh, you know, the average tends to be a 0.7% annual decrease after age 60, you can still offset that by resistance training by staying active. And by eating healthy, getting enough sleep and exercise and good relationships. And all that stuff helps do good mental health helps with all that stuff, too.
Okay, the other myth that’s sort of correlated with this is that menopause causes your metabolism to slow down. And so many women talk about this, that, oh, you know, I’ve hit menopause. And so I’m just gonna, I’ve just gained a bunch of weight. So we’re talking about perimenopausal and postmenopausal women, just understand that the same principles apply, as you get older.
You know, so they did the studies on men and women, and from ages, you know, all the way up to 95 years old. So lots of menopausal women and postmenopausal women. So just going through menopause does not mean you’ll automatically gain weight, whether you are a male or female, whether you’re going through menopause or not.
As you get older, you know, you need to stay active, get good sleep, maintain muscle mass, practice healthy eating habits, get in plenty of protein, that kind of stuff, and you should keep your metabolism going pretty well. Okay, regardless of menopause or age. Cool.
I know that was a big one. A lot of people don’t understand that. And these are pretty new studies. So this is good data that’s coming out here. Love this. Right. Alright, the next myth I want to address is that active people have higher metabolisms.
Okay, so this one is sort of true and false. So I’m gonna, I’m gonna start with why it’s sort of true. So, exercise will temporarily increase your metabolism, but it only lasts about a day or so. Okay, so you might think, oh, yeah, well just exercise every day. And that’ll keep your metabolism going. And that’ll raise your metabolism.
And yes, that’s kind of true, it will. But you have to understand that, you know, your body also needs enough rest and recovery. And if you don’t give your body enough rest and recovery, you are going to chronically elevate stress hormones in your body, you’re going to put your body into this state of chronic stress. And that will actually slow your metabolism down.
So I do know people who love to do these running streaks, and they run three or five, five miles every day, no matter what, and they never give themselves a rest. I’m a little concerned that they’re constantly in a state of stress and slowing their metabolism down.
I’ve told the story about a client of mine who was running at least five kg every day for something like seven straight years and gained about 50 pounds in the process. That shows me that running every day does not really increase your metabolism all that much. Or maybe putting yourself in a state of chronic stress is doing the opposite, having the opposite effect that you know that slight gain in your metabolism has okay.
And this is one of the reasons why I say you can’t outrun a bad diet because exercise alone isn’t going to move the needle that much from a metabolism standpoint. Okay. So, interesting studies they have done on Hadza hunter-gatherers in Tanzania.
So these are groups of people who are very lean, very active, very active people. And it was always thought that their resting metabolic rate was much higher than the typical, you know, American, or whatever. And it turns out that they’re burning about the same number of calories that we do per day.
So Hadza men and women, they walk like four to seven miles a day. They hunt wild game, they harvest honey, they’re digging for tubers, they’re picking berries, they’re fetching water and firewood. They get more activity in a day than the standard American gets in a week.
And surprisingly, the researchers have found that the Hadza don’t burn more calories than the average adults in the US and other industrialized countries. Hadza men burn about 2500 calories a day, Hadza women it’s about 1900. This tracks perfectly with what we know here in the US like what the average Americans, men and women burn per day, the resting metabolic rate.
So, it appears that human energy expenditure is pretty tightly controlled, right? The human body seems to adjust to physical activity by saving energy saving calories on other physiological processes to keep total energy expenditure in check. So your body’s really good at maintaining homeostasis.
And if you’re used to burning 2500 calories, you know, it doesn’t matter how much more activity you’re doing, it’s going to slow some things down. So you’re constantly just burning that 2500 calories. It’s just something interesting to think about. Because being more active isn’t really going to increase your overall metabolism.
Like I said, it does increase your metabolism for a short period of time. Another thing to keep in mind about this is that most of the energy that you burn in a day is really from your resting metabolism, your resting metabolic rate.
So there are three main ways that your body burns energy or uses energy each day. So there’s your resting metabolic rate, your basal metabolism. So this is energy used for your body’s basic functioning, while you’re at rest, you’re sitting on the couch, your body is actually just burning calories. Cool, right?
You can sit there and watch Netflix and know that your body is burning, you know, let’s say it’s around 2500 calories a day. So you know, let’s say it’s just around 100 calories an hour. Cool. Okay, you can go for a run, or you can sit on the couch watching Netflix, and you’re burning about the same amount of calories. So just understand that.
And then number two, the energy, there’s energy used when you break down foods. So this is called the thermic effect of food. I talked about this earlier, when you ingest food, your body actually has to use energy to digest that food. And the thermic effect of food is highest when you’re eating protein.
So you’re going to burn more calories when you eat protein than when you eat carbohydrates and fat. And then thirdly, there’s energy that you use in physical activity. So you have your basal metabolic rate or your resting metabolism, you have the energy used to break down food thermic effect of food, T.F. And then there’s energy used during physical activity.
Your resting metabolism, though, accounts for a huge amount of the total calories you burn each day. Physical activity accounts for about, let’s say about 20% and your resting metabolism. It counts for like 60 to 80% of your total energy. And that digesting of food is just about 10%.
Okay, so think about this. 60 to 80% of your total energy each day is just your resting metabolism, okay. So just understand that when it comes to, you know, trying to outrun your diet or trying to out exercise to get your metabolism, you’re still going to be not really doing much, you’re not moving the needle much compared to what your resting metabolic rate looks like. Okay, all right.
Next myth is that thin people just have naturally faster metabolisms. And this is just not true. So it actually takes more energy for a larger body to function compared to a smaller body. So an overweight person tends to have a faster metabolism than a thin person.
Very overweight people tend to burn way more calories at rest. And they tend to lose weight much faster compared to leaner individuals. So it takes more energy to carry more mass even if, let’s say you kept to people with different body weights and you kept them in bed for an extended period of time.
The heavier person will just have a higher resting metabolic rate just based on their size alone, okay? Also understand that body composition does matter here. Okay, so at a given body weight, someone with a higher amount of lean mass, so lean mass is your connective tissues, muscle and bone.
You really can’t change bone size, you really can’t change your connective tissue size that I’m aware of. But you can control muscle size, okay? So your lean mass, really the one thing that we can concentrate on and actually physically change is our muscle mass. So somebody with a higher amount of muscle mass will burn more calories than someone with less muscle mass.
So think of an athlete and a non athlete with identical body weights, the athlete with a more muscular physique will actually have a higher metabolism. So carrying more lean muscle actually increases your metabolism, this is a good thing.
Similarly, a lean muscular person who weighs 120 pounds, and has a healthy amount of lean mass will have a relatively fast metabolism. But another person who weighs the exact same amount 120 pounds, who has more fat will actually have a slower metabolism.
Okay, so increasing muscle mass is a great way to naturally increase your metabolism. And that’s one of the reasons why I talk about strength training so much. If you’re somebody that wants to, you know, lose weight, improve your body composition, get stronger, improve running, all those things, definitely want to focus on strength training, resistance training to build muscle and build lean muscle.
Okay, next myth, your metabolism cannot change because it’s just genetic. So, understand that your resting metabolism is likely genetic, but you can change your metabolism, you can increase your lean muscle mass, like we just talked about.
Muscle burns more calories at rest, the more muscle you have, the higher your metabolism. Unfortunately, a lot of people don’t want to take responsibility, they don’t want to do the work to improve their metabolism by doing something like resistance training, because it takes some work, it takes some time to get stronger to grow muscles. Okay?
So genetics is at play here, it does provide a predisposition for metabolism. But environmental and lifestyle habits will actually have a positive effect on your metabolism, right. So it doesn’t matter the genes that you’re provided with, it’s always within your ability to improve your metabolic function, and to not necessarily let those genes express themselves to their fullest extent.
Okay, and then this leads me to the last myth I want to talk about today, which is that we can’t control our metabolism. So it’s easy to just blame your metabolism when you’re having trouble losing weight or something like that.
But studies have shown that we do have more control over our metabolism than we previously thought. Some stuff like strength training, getting good quality sleep each night helps to improve your metabolism, reducing stress, drinking more water, consistent resistance training, especially as you get older, building more lean muscle will help with that. Eating less often, these are things we’ve talked about here today.
Maybe just eat two or three times a day, eating enough food each day making sure that you’re getting enough quality protein each day, all these things can help to keep your metabolism going and could lead to improvements in your metabolism even as you get older. Okay.
And then the last thing I’m going to talk about here is, you know, we’re talking about metabolism and burning calories, but we have to think about what we are burning, what calories are we burning, you know, what is the substrate that we are burning?
And eating a diet high in sugar and carbs means that you’re mostly burning glucose, glycogen, sugar and carbs. Okay? If your goal is to lose weight, this is going to make it kind of difficult for you. Losing weight means you want to be burning mostly fat.
So when you ditch the sugar, you ditch the carbs and you get fat adapted, you train your body to be really good at burning fat. This means that you will burn more fat during exercise, but also at rest. So the factors that affect how your metabolism functions, that I’ve talked about here today, can increase either carbohydrate metabolism or fat metabolism.
Obviously, we want to increase our fat metabolism. So as an endurance athlete who also wants to lose fat, you want to increase your fat oxidation. The typical runners’ diet of all the sugar and carbs is probably not going to get you there. Okay. Your body always wants to prioritize that carbohydrate and glucose metabolism.
So ditch that stuff, get your body burning fat. That is the first step. That way when you do increase your metabolism, you will naturally be burning more fat, which is good. Burning fat is how you lose weight. Burning fat is how you improve your endurance as a runner.
Cool. I hope this has been helpful. That’s all I got for you today. Love you all, keep on Running Lean and I’ll talk to you soon.