Fat-Burning Heart Rate Explained: How to Calculate & Achieve It

Determining your heart rate zones is essential for planning appropriate workouts to meet your goals and ensuring you stay safe while exercising (because there is such a thing as “too much”). In addition, your heart rate can tell you a lot about what is happening physiologically during exercise, such as what you are burning for energy, if you are still utilizing oxygen efficiently, or if you are not working hard enough. This article focuses on the “Fat Burning” heart rate zone, how to calculate it, and how to achieve it during your workouts. 

What are Target Heart Rate Zones?

Target heart rate zones are percentages of your maximum heart rate that fall within different aerobic or anaerobic exercise categories. There are five different heart rate zones, each corresponding to a certain intensity. Here is a chart to help explain each heart rate zone:

Zones 1 through 3 are purely aerobic, meaning the body uses oxygen to help burn fats for energy. These are typically moderate intensity workouts and a lower perceived effort so that we can maintain the work for longer periods (over 45 minutes). Zones 4 and 5 become anaerobic, and the body no longer uses oxygen efficiently. Instead, we break down carbohydrates as our main energy source so that our body can use the quickest system possible to create energy for these high-intensity exercise sessions and all-out efforts. Because these zones have us at our maximum effort, it is not safe (nor helpful) to sustain activity at these heart rates for longer than four minutes for Zone 4 and no longer than 40-60 seconds at a time for Zone 5.¹ It is also important to note that you should only train in Zone 4 and 5 for two to three days of the week while most of your exercise routine is in Zones 1 through 3.¹ 

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What is the Fat-Burning Heart Rate Zone?

The fat-burning heart rate zone refers to a specific percentage of your maximum heart rate (or VO2 max) where your body burns more fats for fuel during exercise. This is different from some of the other heart rate zones that utilize more carbohydrates for energy at higher intensity efforts. So, believe it or not, your body is utilizing (or burning) more fats at lower heart rates and lower intensities. Specifically, the fat-burning zone is achieved within Zones 1 through 3 (or 50 to 75 percent of your maximum heart rate). One study found that maximal fat oxidation occurred at 54.2 percent of the VO2 max, equating to about 71 percent maximum heart rate.²

Now, it is important to recognize that weight loss and fat loss are a product of a calorie deficit. So yes, burning fat in the “fat-burning” zone is helpful; however, you must exercise long enough to burn enough calories to be in a deficit. Here are some examples of the calories burned in 30 minutes based on various heart rate percentages (based on a 130-pound, 40-year-old female with an HRmax of 180 bpm).

Based on the formula^3,4,5: Female: Calories/min = (-20.4022 + (0.4472 * Heart Rate) - (0.1263 * Weight) + (0.074 * Age)) / 4.184

Fat-Burning Theory 

The Fat-Burning Theory comes from the idea that different fuel sources are utilized at different exercise intensities. There are certain heart rates at which one will burn more fats and other heart rates at which one will burn more carbohydrates. Research shows that fat oxidation typically occurs during submaximal exercise (45 to 65 percent VO2 max).⁶ Once you reach an intensity that is above 65 percent VO2 max, then you are likely utilizing more carbohydrates to help make energy versus fats (a.k.a the “cross-over point”).⁶ 

Burning Fat vs. Burning Calories

Anytime you engage in an activity that is exercise or simple daily tasks, you are burning calories. Your body requires energy to move, breathe, think, etc., so you can imagine that exercise (which requires a higher heart rate than daily tasks) burns even more calories. However, burning calories does not always mean you are burning fat. 

When exercising at submaximal levels, you burn more fat than carbohydrates. The opposite is true during higher-intensity training. That said, regardless of what fuel source your body is using primarily to create energy, you are always burning calories. Bottom line: you are always burning calories. Sometimes those calories are burned more from carbs; sometimes, it is more from fats. 

How to Calculate It: When Does the Body Start Burning Fat?

Research has found the fat-burning heart rate zone to fall around 70 percent of your maximum heart rate (HRmax) or within a range of about 60 to 75 percent HRmax.^2,6 

Calculating your fat-burning heart rate means first calculating your maximum heart rate. The easiest way to do this is to subtract your age from 220. So, if you are 35 years old, your maximum heart rate is 220-35 = 185 bpm. Then, multiply this number by 70 percent (or 0.70). Your fat-burning heart rate is 185 bpm * 0.70 = 130 bpm. Here is a chart of fat-burning heart rate zones by age:

Fat-Burning Heart Rate Zone vs. Cardio Heart Rate Zone 

You may see the terms “fat-burning heart rate zone” and “cardio heart rate zone” used interchangeably; however, these are two different entities within the world of heart rate training. Remember, there are five heart rate zones to target with exercise, with Zones 4 and 5 being anaerobic (without oxygen). 

All zones can be hit during cardio-based and strength-based exercise; however, the “cardio heart rate zone” refers to the highest intensity (or highest zone) where you are still working aerobically (with oxygen). This is Zone 3 and correlates to 70 to 80 percent of your maximum heart rate. Cardio-based exercise and workouts within this zone have been shown to provide many health benefits, including weight loss, blood sugar control, and stress management.   

How does this differ from the fat-burning heart rate zone? The cardio heart rate zone is at a slightly higher intensity than fat-burning heart rates, and your body is thus required to use a little more carbohydrates for energy to sustain the workload. So, you will burn less overall energy from fats in the cardio heart rate zone than in the fat-burning heart rate zone. Again, a high fat-burning heart rate zone falls between 60 to 70 percent of your maximum heart rate. 

What is the Best Fat-Burning Exercise? 

The workout that targets your fat-burning zone may differ from everyone else, so it is important to know your resting heart rate, maximum heart rate, and target heart rates before choosing the right workout. Here is a list of exercises perfect for getting into the fat-burning zone, but make sure to track your heart rate while you work out!

1. Slow jogging: this should feel easier than actual running and be slower than 6 mph on average. You can do this outside or on a treadmill and take breaks as you need. 
2. Walking: walking is one of the best forms of exercise as it is low-impact and easier on your joints than jogging or running. You can pick up the pace to increase your heart rate or find some hills to make the effort a little harder. Obtain the right amount of steps per day for the ultimate weight loss plan.    
3. Cycling: whether indoors or outside on your bike, cycling is another low-intensity exercise that is great for dialing in a fat-burning heart rate zone. If needed, add resistance or find a hilly route outside to increase the difficulty.  
4. Swimming: swimming is a full-body workout that, for some, will feel more vigorous than others. Start with easy laps in a pool while taking rest breaks between laps to keep your heart rate under control.  
5. Interval training: you may be more familiar with high-intensity exercise (HIIT); however, you can keep this type of exercise in a lower-intensity fat-burning zone by increasing the rest intervals and reducing the difficulty of the exercises. 
6. Water aerobics: this can be a fun way to work out in a social environment while getting a great workout. Water aerobics combines the resistance of the water with full-body exercises to help increase strength and cardiovascular endurance. 

A workout that targets fat loss should remain within 60 to 70 percent of your maximum heart rate and be performed for at least 150 minutes each week, according to the Physical Activity Guidelines for Adults by the American Heart Association.⁷ Here is a sample 1-week plan that includes cardio and weight-based fat-burning workouts:

Tools to Use to Measure Heart Rate 

As we’ve mentioned, tracking your heart rate during exercise is crucial for maintaining safety and ensuring you hit the rate goals during your workout. There are many devices you can use to help you track your heart rate at rest and during exercise, including watches, mobile phone apps, chest straps, and checking your pulse manually. 

The easiest way to measure your heart rate is with a watch, app, or chest strap. You can check your watch periodically throughout your workout to see if you are hitting 60 to 70 percent of your maximum heart rate and also view your average heart rate for a single session at the end. Garmin, Apple, and Fitbit watches all provide this data in real time. Apps on your phone that track heart rate include Cardiio, Google Fit, Apple Health, and Cardiograph. Chest straps tend to be more accurate than watches or phone apps; however, they can be more expensive and sometimes uncomfortable to wear.⁸ Examples of chest straps include the Polar H10, Wahoo TickrX, and Garmin HRM Pro.⁹ 

If you don't want to purchase an app or device, you can simply check your pulse and use a watch to calculate your current heart rate. First, find your pulse just underneath your jaw or on the inside of your wrist. Find the pulse, and use a clock to count each beat over six seconds. Then, multiply this number by 10 to get your heart rate. 

6 Other Effective Ways to Lose Fat 

Reaching your fat loss goals means more than just exercise. In fact, it is possible to lose fat without exercise at all.¹⁰ It is also important to note that fat loss and weight loss are different, so understanding which one is right for you helps you reach your specific goals. Here are six other lifestyle habits to focus on outside of exercise if you need to lose fat.  

1. Keep hydrated: drinking water helps promote lipid oxidation (fat burning), and research shows that being consistently dehydrated leads to increased bodyweight.¹¹ 
2. Focus on whole foods: eating a balance of macronutrients (carbs, proteins, fats) and colorful fruits and vegetables is a great diet to follow for general health and weight loss. One example of this is the Mediterranean diet.  
3. Go for a slow and gradual weight loss: achieving weight loss too quickly can harm your body and lead to unsuccessful long-term results. A loss of more than 2 pounds per week is considered unsafe.¹² 
4. Mind portion sizes: Calories in vs. calories out (a caloric deficit) is an important equation for successful weight loss. Be mindful of your portion sizes when putting together a meal or snack to make sure you are staying within a healthy range of caloric deficit.  
5. Improve your gut health:  Research has shown a positive correlation between a healthy gut microbiome, weight loss, and reduced chronic disease, including diabetes, cardiovascular disease, and obesity.¹³ 
6. Keep in mind your metabolic rate: Your resting metabolic rate is the number of calories your body requires to function (i.e., breathe, pump your heart, fire your neurons, etc.). In addition, your body requires calories to perform daily tasks, such as cooking, cleaning, and moving about the house. Any calories burned beyond this will be the calories you burn for weight loss. Keep this in mind as you calculate your caloric needs.

Learn More About How to Achieve Better Health Through Exercise with Signos’ Expert Advice.

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