I’ll start with the bottom line: fat loss is a complicated process. There is no guarantee that working out at a certain heart rate will lead to fat loss. I’ll explain, but first, I need to explain target heart rate…
Target Heart Rate
The idea behind target heart rate is to determine your exercise intensity. The faster your heart beats during exercise, the more benefits to your heart (theoretically). Supposedly this benefit peaks at a certain heart rate, which is the target heart rate. The thinking is, if you reach this target, you will get the most benefit.
What is Your Target?
There is a relatively simple way to figure out what your target heart rate should be. It’s so simple in fact, that many gyms own cardio machines that will do this math for you. You just have to enter a couple of pieces of personal information, and boom, it will tell you your target heart rate.
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Checking Your Heart Rate
What happens when you hit this target while you’re working out?
To know whether you hit this, you will either need to manually check your heart rate or wear some sort of heart rate monitor. Just know that each of these have their pluses and minuses.
For example, when you’re calculating your own heart rate by checking your pulse, the first beat you hear or feel isn’t counted. The second beat is actually the first one you count. Then you need to keep counting beats for at least 15 seconds. Once you have done that, multiply the number you get by 4. That will you give you your heart rate in beats per minute. If you’re not great at checking your own pulse, this will lead to some errors.
If you’re using a heart rate monitor, they must be worn properly to ensure accuracy.
I’m trying to point out that tracking heart rate may lead to some accuracy issues. If we can’t accurately track our heart rate, then we really don’t know for sure if we achieved our target.
What Type of Fuel Do Our Bodies Burn at Our Target Heart Rate?
According to the American College of Sports Medicine, when we're working at a certain percentage of our target heart rate, we are more likely to burn muscle fat. Note the keyword: muscle fat.
Muscle fat is different than body fat. But even then, working out at your target heart rate doesn’t guarantee you will burn any fat all–muscle or body.
Some of the other factors that can influence whether we burn fat during exercise can include:
- your current level of fitness
- your age
- your gender
- how much muscle you have
- the type of exercise you’re doing
- what you ate before your workou
And so on.
To try and predict whether you’re burning fat during your workout is a bit challenging.
Mix up your workout routines.
For example, there are studies that support high intensity interval training as a way to help burn fat. When performing high intensity interval training, folks are often surpassing their target heart rate. Yet it was found that these folks are still burning fat.
Then there are other studies that support lower intensity exercise as a way to burn more fat.
This is why I say that incorporating variety into your workouts is probably the best thing to do.
Incorporate low- and high-intensity cardio. Definitely add resistance training into your routine. The more muscle you carry, the more calories you burn all the time. And hopefully, some of those calories being burned are coming from fat!
Workaround For Measuring Heart Rate
Remember how I was complaining about all the problems with measuring heart rate? Here’s an easy workaround:
When you’re in the middle of your workout, are you be able to hold a conversation, or are you breathing so hard there’s no way you can imagine uttering a single word? If you’re able to hold a conversation, and you’re hoping to get closer to your target heart rate, you probably need to increase the intensity. If you’re breathing so hard that you’re just trying to avoid passing out, you can take the intensity down a notch (unless, of course, your goal is to get to that point). If you want to exercise within your target heart rate range, get to the point where you can talk but can’t hold a conversation.
That’s one of the better ways to make sure you’re hitting your target!
Is There Such a thing as a Fat Burning Heart Rate Zone in Exercise?
QUESTION: “Hi Dr. Neal, I have been listening to your podcast for over a year and I love it! You have taught me so much. My question is: is there such a thing as a fat burning heart rate zone in exercise? And if there is, what does it do? Thank you for your answer and for your great work.”
Dr. NEAL: Thank you so much for taking the time to send in your question. I am thrilled that you found us and that the show has been helpful.
Listen to Dr. Neal address this topic on Episode 1316 of the podcast Optimal Health Daily.
Traditional Thinking about Fat Burning
I still remember, I was taking my first Exercise Physiology class in graduate school. We had just spent 2 weeks discussing all of the crazy metabolic pathways – how the body burns certain nutrients at different intensities and heart rates and why all of this happens.
Then at the end of those 2 weeks, when I felt like I finally understood everything, my professor asked the class: “So, why would it be incorrect for you to force a client to stay in their ‘fat burning heart rate zone’ when exercising?” I was like, “Wait, didn’t we just spend the past 2 weeks discussing why this was a good idea?”
Luckily, my professor didn’t call on me because that probably would have been my response – well, that or a blank stare.
Instead, one of the brightest people in my entire graduate program spoke up and said, “Well, it’s misleading because the body will ultimately determine whether to burn fat or not – and this isn’t based on just exercise intensity or heart rate. It’s based on a bunch of things. The body will burn calories when exercising, but ultimately decides where to pull those calories from. It could be fat or it could be something else.”
My professor responded with one word: “Exactly.” I nodded in agreement just so I looked like I knew what was going on, but I didn’t. My face must’ve looked like Joey Tribbiani’s from “Friends” when the gang was talking about the PBS special on the history of Korea – nodding in agreement but secretly panicking on the inside.
Fat-Burning Heartrate Zones are Only Half the Story
It took me a while… a long while… and a deep dive into the research to figure out just what my super bright colleague meant. But here’s what I was initially believed, like so many others: when you workout at a certain intensity, you can burn more fat.
Well, this is only about 50% correct. First, what does heart rate have to do with workout intensity? Well, the more intense the workout, the faster our heartrate (or pulse) will be. And the higher our heartrate during exercise, the more likely the body will turn to other sources of exercise fuel besides fat.
In fact, the body is more likely to use stored sugar (also known as glycogen) as fuel as the intensity increases. So, if we keep our heartrate, or basically exercise intensity, at a moderate level, we may burn more fat. That’s why you see these fat-burning heartrate zones on a bunch of cardio machines. But here’s where it gets a bit fuzzier.
Keeping your heartrate in these fat burning zones may burn fat or may not. Whether or not this happens is, just like my colleague graduate school said, is based on a lot of things.
Your current fitness level is one factor. What you ate before the workout. When you ate. Your age. Your gender. Your muscle mass. How long you stay on the machine. Oh, and the machines never tell you whether any fat that is being burned comes from. If the body does burn fat during the workout, it’s fat that’s found near the muscle – not the fat around the belly button. It’s the fat that’s surrounding the muscle which is not as harmful to our health as the previously mentioned fat around the belly button.
Fat around the belly button is much more dangerous to our health. We want to burn fat around the belly button.
What It Takes to Burn Body Fat
To burn fat around the belly button – well, that takes more than just working out in the “fat burning zone.” In fact, it may require just the opposite.
Studies are finding that high intensity activities may be useful for burning body fat. But, performing high intensity interval training for example, is not enough. It will help, but we need to perform resistance training to make our muscles larger.
We need to throw in some lighter intensity cardio, too. We need to stay consistently active for weeks, months, and years. We need to occasionally switch up our routines (like we talked about earlier this week) to keep the body adapting and prevent injury.
Oh, and let’s not forget about diet. All of these sound like a lot, but it doesn’t have to be. Start somewhere… like ignoring those fat burning zone charts on those cardio machines.
Listen to Dr. Neal address this topic on Episode 1316 of the podcast Optimal Health Daily.