Muscle for Life with Mike Matthews - What Is the “Fat-Burning Zone” and Does It Matter?

Episode Date: August 2, 2021

In this podcast, we’re going to talk about the “fat burning zone,” which is something you’ve probably heard about many times. When I first got into fitness, I read that if you’re doing cardio to lose fat, you better be doing it in the “fat burning zone.” If you don’t, proponents claim, your cardio is going to be a lot less effective, or maybe even completely ineffective. You’ll simply end up burning through the glycogen in your muscles or the carbs in your blood, leaving your body fat untouched and unscathed. This idea has stood the test of time, too. It’s been around for at least 50 years now, and many people think the fat burning zone is the ticket to losing weight. As you’re going to learn in this podcast, the fat burning zone is largely a myth. Lower-intensity cardio that burns a larger proportion of fat isn’t necessarily better than higher-intensity exercise when it comes to overall fat loss. That doesn’t mean you have to do a lot of high-intensity cardio either, though. Find out why by listening to this episode! Timestamps: 3:57 - What is the fat burning zone? 9:57 - What's wrong with the fat burning zone idea? 15:19 - What’s the best kind of cardio for burning fat? Mentioned on the Show: Shop Legion Supplements Here: https://buylegion.com/mike

Howdy, howdy, welcome to Muscle for Life. I'm Mike Matthews, thank you for joining me today. And if you like what I'm doing here, please do subscribe to the show in whatever app you're using because it helps boost the rankings of it so other people find it more easily and it makes sure that you get notified when I publish new episodes

so you never miss a vital installment of Muscle for Life. All right, so in today's episode, we're going to be talking about the fat burning zone, something I'm sure you've heard about many times. I know I have going all the way back to the beginning of my foray into fitness when I was 17, 18 years old. I remember reading in the bodybuilding magazines how if you're going to do cardio to get lean, and you have to do cardio to get lean, of course, then you need to be doing it in the fat burning zone. And if you are not in the fat burning zone, then your cardio is going to be a lot less effective for losing fat, or might be completely ineffective. It might only burn the glycogen in your muscles, for example,

or it might only burn carbohydrates in your blood from the food that you ate. Common claims, right? Now, this idea has had impressive longevity. It has been around for at least 50 years now. And in that time, many other workout trends have come and gone. And some do make comebacks because of the cyclical nature of things. But the fat burning zone idea, myth, as you're about to learn, has remained pretty steady, pretty constant in regular circulation again for several decades. People still think that that's the ticket. That's how you get lean. And yes, this is largely a myth, at least the way that most people understand it. And what that means then is if you're doing all of your cardio

workouts in a low to moderate intensity, yes, you can lose fat with that, but that is not necessarily better for losing fat than doing higher intensity cardio. And again, as you're going to learn in this episode, the higher intensity cardio is strictly speaking more time efficient for losing fat because you're going to lose more fat in a shorter amount of time. But that doesn't mean that you have to do a bunch of high intensity cardio either. Also, if you like what I am doing here on the podcast and elsewhere, definitely check out my sports nutrition company, Legion, which thanks to the support of many people like you is the leading brand of all natural sports supplements in the world. And we're on top because every ingredient and dose in every

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build muscle, and get healthy faster, and you will find the best of them in Legion's products. To check out everything we have to offer, including protein powders and bars, pre-workout and post-workout supplements, fat burners, multivitamins, joint support, and more, head over to buylegion.com slash Mike. That's B-U-Y-L-E-G-I-O-N.com slash Mike. And just to show you how much I appreciate my podcast peeps, use the coupon code MFL at checkout, and you will save 20% on your entire first order. Okay. So what is the fat burning zone? Well, this refers to a workout intensity where your body is burning mostly fat. And the

idea is by working mostly in this zone, which is related to your heart rate, and I'll get into that in a second, you are going to mostly lose fat in your workouts. And that is going to result in more fat loss over time than doing cardio in a different zone, in a carbohydrate burning zone, for example, a higher intensity zone. Now, this is also referred to as the fat burning heart rate zone because the intensity of the training is often expressed as a percentage of your maximum heart rate. So this is where it takes a technical term and it has a scientific flair about it. Now, in order to understand how this idea came about, you have to understand how your metabolism works when you exercise. So when you're training, your body is

using several different sources of energy to power your workout and to stay alive. And the main ones are carbohydrate and fat. Now, it uses different physiological processes, and these are known as energy systems to transform carbs and fats into usable energy for your cells because your cells can't use molecules of carbohydrate or dietary fat. They have to be broken down into smaller things that your cells can use. Now, when you are at rest, when your heart rate is low, your body is getting almost all of its energy from fat. And that is a very efficient and it's a very plentiful fuel source. It is very easy to transform body fat into usable energy at a cellular level. Now at rest, of course, you're not burning many calories. It doesn't cost much energy to just sit there. And as body fat is

pretty energy dense, a pound of body fat contains about 3,500 calories. And to put that in perspective, I'm 193 pounds and I'm a lot more muscular than the average person. So my 193 pounds costs more energy to use and to maintain than someone else who weighs 193 pounds, but who has a lot less muscle. And Monday through Friday, I'm in the gym lifting weights for about an hour per day. And I do about 30 minutes of low intensity or low slash moderate-ish intensity cardio. I hop on an upright bike and I usually make or take work phone calls during that time. And then on the weekends, Saturday and Sunday, I usually do just the cardio, 30 minutes or so. And to maintain my weight, so my maintenance calories are around 3,000 to maybe 3,200 per day. And so one pound of body fat has over an entire

day's worth of energy for me, going into the gym, doing my cardio. Otherwise, I'm not very active. I'm just sitting on my computer typing or recording podcasts. But on the whole, if you look at my activity level, it is pretty good because I'm exercising 12 to 13 hours per week. And I'm fairly lean. I'm around probably 9% body fat, maybe 10%. So let's just say I have 20 pounds of fat. That's what I'm carrying around. That's probably about a month's worth of energy at my current activity level, meaning I could survive off of just my body fat for probably about a month, no food. So anyway, my point with all of that is body fat is very energy dense and it's very easy to turn into cellular energy. So that is the first resort of our body.

Whenever it needs energy for anything, if it doesn't have energy available from food that we just ate or ate some time ago that it is still digesting and absorbing. All right, so let's come back to this point of us being at rest and our body getting most of the energy it needs from body fat. Again, assuming that it can't get the energy it needs from food that we ate because it's already done processing it. You can burn more energy, of course, by moving around and you can move around more intensely to burn even more energy. But there is a side effect here. Yes, fat burning goes up. However, the energy system that burns fat for energy isn't able to keep up with the demand for energy and particularly from your muscles as you are lifting weights or doing cardio or playing a sport or whatever. And so then what happens is the body starts to metabolize more and more carbohydrate. That energy

system kicks in to pick up the slack. And once you're exercising at about 60 to 80% of your maximum heart rate, studies show that your body gets about half of its energy from carbohydrate stores and half from fat stores. And this is a point that scientists refer to as your maximal fat oxidation rate or MFO. Now, if you push even further than that, if you are pushing to near maximal intensities in your training, think sprinting, for example, or a higher rep set of maybe squats taken close to muscular failure, think like a 10 rep set, for example, what happens is your muscles start getting the majority of the energy they need to do that from carbs and very little from fat. And so if you just connect those dots, you see how this fat burning zone idea came about.

The theory was, hmm, if we want to lose as much fat as possible from our workouts, maybe we should work out at the intensity at which our body burns as many calories as possible while still getting the majority of those calories from fat and not carbs. Sounds nice, but there are a few reasons why it's all hat and no cattle. So the first and biggest problem with this idea is that the amount of fat you burn during a workout isn't all that important when it comes to long-term fat loss. You see, when you burn more fat and less carbs during a workout, you just burn less fat and more carbs later in the day and vice versa. And the reason for this is studies show that our body will calibrate how much fat in carbohydrate it burns over a 24-hour period

to make sure that it's burning the same amount in terms of proportions, regardless of what we burn during our workouts. So for example, let's say you burn 400 calories during an intense 30-minute run, and most of those calories are coming from carbs because it's high intensity, and your body's fat-based energy system just can't keep up. minute run. And most of those calories are coming from carbs because it's high intensity in your body's fat-based energy system just can't keep up. And then the next day you burn 400 calories on a 90 minute walk. And most of those calories will come from fat because that's a low intensity activity that your body's fat-based energy system can keep up with. Now, which of those workouts will burn more body fat?

Well, many people who believe in the fat-burning zone will say, oh, the 90-minute walk, but they're wrong. You'll burn about the same amount of body fat. So the key takeaway here then is in the context of fat burning, all that really matters in your exercise, in your training, in your workouts is calorie burning. That is what drives fat loss, not the intensity of the training. Now, the intensity of training drives calorie burning, very true,

but calories are calories. Energy balance works very simply regardless of what type of exercise you're doing. The second problem with the fat burning zone idea is the way that most people implement it. So what they are often told is they need to hold themselves back in their training. They need to do relatively easy workouts. And that's what the fat burning zone workouts are if you are even moderately fit. And they then will not do moderate or higher intensity workouts because they think that those sessions are not going to be as effective for fat burning because they are not in the fat burning zone. As I mentioned a few minutes ago, though, technically the fat burning zone is up to 80% of your maximum heart rate.

And that's something that most people would consider a pretty difficult workout. That's a moderate or even a fairly high intensity training session. So for instance, let's say you do something very easy. Let's say you go for a walk and you burn off a hundred calories and the majority of those come from fat. Let's say 85 of them come from fat. That is not going to be as effective as spending that time doing something more difficult. Let's say running at a moderate pace, which yes, will burn fewer calories from fat relatively speaking, but more in an absolute sense. So let's say in the same time you burn 400 calories on that run and 250 of them come from fat. Or maybe you burn 600 calories on a slightly more intense run or maybe a bike ride or something like that. And half of

them, just 50% come from fat, but that's 300 calories come from fat. So in a relative sense, yeah, the hundred calorie walk was quote unquote more efficient for fat burning, but in an absolute sense, the higher intensity workout was a lot more effective. Now, the last problem with the fat burning zone myth is that it implies it's a static intensity that occurs at a very specific heart rate. And cardio machines often reinforce this by showing pretty graphs and they try to indicate exactly where your heart rate should be

for fat burning versus cardiovascular training. And the reality though is the fat burning zone or more accurately, the term I shared earlier, your maximal rate of fat oxidation can vary widely depending on your fitness level and sex. Specifically, people who are in better shape burn a higher percentage of fat at a higher intensity than people who are less fit because studies show that exercise improves your ability to metabolize fat for energy at higher intensities. And on the flip side, studies show that very low intensity exercise can max out the

fat burning abilities of obese people, that they can reach their maximal rate of fat oxidation at, for example, just 24% of their VO2 max, which is the maximum amount of oxygen you can metabolize during exercise. It's another measure of exercise intensity. And then if we look at research on very fit people, on endurance athletes, we see that in some cases, they don't reach their maximal rate of fat oxidation until they're close to 80% of their VO2 max. Studies also show that women burn a higher percentage of calories from fat than men do at most exercise intensities. So my point with all of this is the fat burning zone is a moving target. You're never going to be able to pinpoint it exactly. Now, fortunately, you don't have to because it's not necessary. It's not even useful

to do so. And all of that then brings me to a question, which is what kind of cardio is best for burning fat? And the answer is something you've probably guessed by now. It's very simple. It is whatever burns the most calories. That's it. Now that doesn't mean I'm telling you to only do very, very high intensity cardio to only do hit, for example, because while HIIT does burn the most calories in the least amount of time, it is also pretty hard on your body. Even if you choose something that is low impact like biking or rowing or swimming, it places additional recovery demands on your body. And if you're listening to this show, you're probably doing a fair amount of weightlifting, a fair amount of strength training, and your priority is to progress there and to make sure you are fully recovering from those workouts.

And in that case, I would not recommend doing a bunch of HIIT. If you want to do some because you want to get the extra calorie burning or the extra cardiovascular endurance, then I'd recommend capping it at probably about an hour per week. And I would split that up into two or three sessions. So then the best fat loss cardio regimen for you is going to be the one that allows you to burn the most additional calories over time. So let's say you're going to be cutting for a few months. We have to look at it from that perspective. And when we look at cardio through that lens, we realize that just a couple of hit sessions per week is inferior to twice or maybe even three times as many lower intensity sessions per week.

If we're just looking at fat burning, assuming you're not trying to do one hour hit sessions, you're not trying to die basically. And the longer term perspective also makes it clear that you need to be doing cardio that you enjoy or at least that you don't hate and unless you have a masochistic streak you probably don't really enjoy very high intensity cardio you probably more enjoy what i do hop on a bike 30 minutes work up a sweat push yourself to an effort level of maybe a four or five out of 10, where you're breathing more heavily throughout your workout, but you can still have a conversation. Maybe you have to catch your breath now and then, and burn a few hundred calories and take a shower

and move on with your day. And so then that's my general answer when people ask what type of cardio they should do or what type of cardio routine they should do to lose fat faster. A fair amount of low slash moderate intensity stuff with small amounts of high intensity stuff if they feel up to it. All right. Well, that's it for this episode. I hope you enjoyed it and found it interesting and helpful. it interesting and helpful. And if you did, and you don't mind doing me a favor, please do leave a quick review on iTunes or wherever you're listening to me from in whichever app you're listening to me in, because that not only convinces people that they should check out the show,

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for listening to this episode, and I hope to hear from you soon.