The Fat Burning Heart Rate Zone + How To Calculate Your Zone 2 HR

Cracking the fat burning code, delving into exercise intensity for optimal results.

If you look around at the setting people are using on cardio equipment at the gym, you’ll notice most are exercising in the “fat burning zone” with the ultimate goal of losing weight and burning fat.

The fat burning heart rate zone is often depicted as a sweet spot for “fat burning”, typically falling between 50-70% of your maximum heart rate.

At this intensity, the body is said to predominantly utilize fat stores for energy, making it an attractive option for those looking to burn fat.

However, low-intensity workouts may not burn as many calories overall as higher-intensity exercise.

So, what exercise options are best for fat burning? Let’s explore the truth behind the fat burning heart rate zone, its implications, and whether it’s something you should focus on during your workouts.

A person taking their heart rate.

What Is The Fat Burning Heart Rate Zone

Before we look specifically at the target heart rate to burn fat or the “fat burn heart rate zone,” what exactly do we mean by heart rate zone for fat burning?

Fitness professionals typically use five different heart rate zones to help quantify the intensity of exercise based on how fast your heart is beating during your workout relative to your maximum heart rate.

Cardio machines may refer to a “fat burning zone,” which is usually the upper end of Zone 2 where you are burning more fat for fuel instead of carbohydrates.

Most people don’t know their true maximum heart rate unless they do a VO2 max test or maximum heart rate test, so we typically estimate maximum heart rate based on age because there is an inverse linear relation in maximum heart rate.

Essentially, the older you get, the lower your maximum heart rate is in a fairly predictable manner.

A heart drawn in chalk.

How To Calculate Your Zone 2 Heart Rate

How do I calculate my fat burning heart rate zone?

A simple formula for estimating your age-predicted maximum heart rate is 220 minus your age. 1CDC. (2019, December 4). Target Heart Rate and Estimated Maximum Heart Rate | Physical Activity | CDC. Www.cdc.gov. https://www.cdc.gov/physicalactivity/basics/measuring/heartrate.htm

This formula has quite a large margin of error, but it should serve as a decent estimation for most individuals. Use a heart rate monitor, and perform a sprint session for specific max heart rate values.

For example, if you are 40 years old, your age-predicted maximum heart rate is 220-40 = 180 heart beats per minute. 

Once you know your age-predicted max heart rate or true maximum heart rate, you calculate your target Zone 2 heart rate zones using the percentages of max HR.

Not all fitness professionals agree on a precise target heart rate range for the fat burning zone, but it is generally somewhere between 50 and 75% of your max heart rate or 60 and 75% of your max heart rate.

One study determined that maximal fat oxidation occurred at 54.2 percent of VO2 max, which corresponds to about 71 percent maximum heart rate.2Carey, D. G. (2009). Quantifying Differences in the “Fat Burning” Zone and the Aerobic Zone: Implications For Training. Journal of Strength and Conditioning Research23(7), 2090–2095. https://doi.org/10.1519/jsc.0b013e3181bac5c5

The “cardio zone“ is also a little bit loose in terms of definition, but it’s usually somewhere between about 70 and 75% to 85/88% of your maximum heart rate.3Habibi, E., Dehghan, H., Moghiseh, M., & Hasanzadeh, A. (2014). Study of the relationship between the aerobic capacity (VO2 max) and the rating of perceived exertion based on the measurement of heart beat in the metal industries Esfahan. Journal of Education and Health Promotion3(55), 55. https://doi.org/10.4103/2277-9531.134751

For example, if we use 180 bpm as the maximum heart rate, here are the target heart rate zones:

  • Zone 1: 50-60% = 90-108 bpm (aerobic exercise)
  • Zone 2: 60-70% = 108-126 bpm (aerobic zone)
  • Zone 3: 70-80% = 126-144 bpm (moderate exercise)
  • Zone 4: 80-90% = 144-162 bpm (anaerobic zone)
  • Zone 5: 90-100% = 162-180 bpm (maximum effort)

So where does the fat burn heart rate zone fit in? 

A person running with a heart rate monitor.

Does Exercise In The Fat Burn Heart Rate Zone Burn More Fat Than The Cardio Zone?

Which heart rate zone burns the most fat? The fat burning zone or the cardio zone?

There is a lot of confusion about whether the fat burn vs cardio zone burns more fat and is better for weight loss.

Even though fitness professionals use the term “fat burn heart rate zone,” exercise can help you lose body fat in several ways. 

  1. To fuel your muscles when you exercise, your body burns stored fat to provide the calories necessary to generate ATP (energy for your muscles to contract).
  2. Following a consistent workout routine can help you lose fat if you’re generating a caloric deficit (burning more calories in the day with your workouts, BMR, and physical activity compared to the number of calories that you are eating).
  3. Certain types of workouts increase your metabolic rate and affect your hormones, which can help you burn more calories, even at rest, ultimately supporting fat loss over time.

The “fat burning heart rate zone” is related to the first of these three listed ways in which exercise primarily supports fat loss.

Let’s dive in in more detail.

People doing squats.

Does The Fat Burning Zone Really Exist?

Basically, fat burning heart rate zone workouts are performed at the intensity at which you are maximizing how much body fat you are burning. 

So, in a fat-burn zone workout, your body is burning a higher percentage of the calories that you need for that exercise from fat rather than from carbohydrates.

By understanding how glucose and stored fat serve as fuel sources during exercise, we can optimize our workouts to reap maximum health benefits and achieve your body weight and fitness goals.

But what does this mean, exactly?

Any type of physical activity or exercise requires your muscles to contract and your heart to beat harder and faster, all of which require energy.

To create this energy, there are various metabolic pathways that turn stored fuel into usable energy for your muscles (ATP). 

This stored fuel comes from a combination of stored carbohydrates (glycogen in muscles and the liver), stored fat (triglycerides in adipose, or fat, tissue), and stored protein in muscle tissue.

At pretty much any given exercise intensity, you’re burning some of every type of fuel to get the calories needed to create ATP.

People running on treadmills.

By and large, carbohydrates and fat are the primary fuel sources for the muscles during exercise, with a much smaller contribution of calories for exercise coming from protein.

This is unless you are in a state of starvation or following an insufficient diet, exercising extremely intensely, or doing very long workouts.

Generally speaking, protein usually provides less than 10% of the total energy needed for exercise.

Except in extreme situations such as starvation, ketosis, or very long and intense workouts, so it is not usually factored into determining calories from carbs vs fat during exercise.

That aside, the relative percentage of carbohydrates vs fat burning as the fuel your body oxidizes for energy depends on the intensity and duration of the workout.

As the cardio exercise intensity increases, the relative percentage of carbohydrates increases, and the percentage of calories coming from fat decreases.4Patel, H., Alkhawam, H., Madanieh, R., Shah, N., Kosmas, C. E., & Vittorio, T. J. (2017). Aerobic vs anaerobic exercise training effects on the cardiovascular system. World Journal of Cardiology9(2), 134. https://doi.org/10.4330/wjc.v9.i2.134

Therefore, your muscles are primarily burning fat for fuel when you are doing workouts with your heart rate in zone 1 or zone 2, whereas more glycogen (stored carbs) is burned for workouts in zones 3, 4, and 5.

This is why fat burn zone vs cardio zone workouts are done at a lower heart rate. 

Said another way, and simplified to some degree, at lower intensities of exercise, fat is the primary fuel.

That’s why exercise machines that have a pre-programmed workout in the “fat-burning zone” have you moving at a slower pace or easier or moderate intensity than cardiovascular zone workouts.

A person running with a heart rate monitor.

Is The Fat Burn vs Cardio Heart Rate Zone Better For Weight Loss?

If you are trying to maximize how much fat you burn, exercising in the fat burning heart rate zone may seem like the most effective approach, but this isn’t necessarily the case.

When you work out more vigorously, although the percentage of calories from burning carbs is higher, and the lower your heart rate during exercise, the greater the percentage of calories do come from fat, vigorous exercise burns a greater number of calories overall.

Because a caloric deficit is necessary to ultimately lose fat5Strasser, B., & Fuchs, D. (2016). Diet versus Exercise in Weight Loss and Maintenance: Focus on Tryptophan. International Journal of Tryptophan Research9, IJTR.S33385. https://doi.org/10.4137/ijtr.s33385, in almost all cases, a more vigorous or intense workout in the cardio vs fat burn heart rate zone will burn more total calories.

More calories from fat too, even though the relative percentage of these calories from fat decreases.

What this means practically is that even if you are working out above the target heart rate zone for fat burning, you still might burn more calories from fat during an intense workout.

A person on a stationary bike.

Consider the following scenario:

If you ride a stationary bike at a low aerobic intensity (heart rate in zone 2) for 30 minutes, you might burn 200 calories, of which 60% come from fat, and 40% come from carbohydrates.

Therefore, in this example scenario, you would burn 120 calories from fat and 80 calories from carbohydrates for your workout.

Then, imagine you do a hard workout on an exercise bike where your heart rate is mostly in the cardio vs fat burn zone (zones 3-5). 

Again, you bike for 30 minutes, but this time, because you are cycling much harder and your heart rate is higher, you burn 400 calories in 30 minutes.

Because the exercise is of higher intensity, 60% of the energy comes from carbs, and 40% comes from fat.

This means that the vigorous bike workout burned 240 calories from carbohydrates and 160 calories from fat. 

A person looking at their running watch.

Therefore, even though the percentage of calories from fat was lower, you still burned more calories from fat than you did during the low-intensity “fat-burning heart rate zone” workout.

Plus, regardless of whether the calories you are burning during exercise come from fat vs carbs/glycogen, all that matters for losing body fat is the total number of calories you burn: as long as you create a caloric deficit, you will lose fat.

A caloric deficit of 3,500 calories will result in one pound of fat loss.

Finally, more intense exercise, such as high-intensity interval training, can help boost your metabolism, which can also contribute to burning more calories and losing more fat over time.

It is important to keep in mind that although exercising in the “fat burn heart rate zone“ will not necessarily burn more body fat in the long term than incorporating more vigorous workouts.

Final Thoughts

While exercising in the fat burning zone may enhance fat oxidation, it’s crucial to consider the broader context.

Total calorie expenditure, influenced by individual factors like fitness level and exercise intensity is paramount for weight management. W

hile high-intensity workouts and HIIT sessions offer efficient calorie burning, incorporating moderate and low-intensity exercises like brisk walking can contribute to overall physical activity guidelines. 6Centers for Disease Control and Prevention. (2022). How Much Physical Activity do Adults Need? Centers for Disease Control and Prevention. https://www.cdc.gov/physicalactivity/basics/adults/index.htm

‌Seeking medical advice and guidance from a personal trainer can help tailor workouts to individual needs, promoting heart health and reducing the risk of obesity and heart disease.

To learn more about heart rate training and a full heart rate chart, check out our guide to how to calculate your heart rate zone:

References

Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

1 thought on “The Fat Burning Heart Rate Zone + How To Calculate Your Zone 2 HR”

  1. Very informative article, however I believe that age-based formulas for max heart rate are flawed. I have never done an actual max HR test, however at age 60 during hard effort races from 10k up to half marathon I can maintain my pace with a HR above 170 and finish over 180. I also would like to see a comparison between the percentage of max formula and the formulas that use heart rate reserve such as the Karvonen method.

    Reply

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.