Is There a Secret 'Fat Burning Heart Rate'? We Investigate

Have you ever spent hours trying to stay within a certain heart rate, wondering if it’s the key to slimming down? As a physical therapist, I’ve worked with many people chasing this target.

Athletes have monitored their heart rates for decades, but it’s become much more popular for the average gym-goer thanks to the rise in wearable fitness trackers.

But is there really a secret ‘fat-burning heart rate’? Or is it just another fitness myth? In this article, we explore the basics of heart rate, whether there’s a magic fat-burning zone, and give practical tips for healthy weight loss.

Understanding the basics of heart rate

Your heart rate tells you how hard your body is working during exercise. As you move more, your muscles need more oxygen, so your heart beats faster to deliver it.

Over time, regular exercise can lower your resting heart rate as your heart starts to work more efficiently — a low resting heart rate is common in well-trained athletes. Tracking your heart rate helps personalize training to your fitness goals, and can help you make sure you’re not over- or undertraining.

The five heart rate zones are intensity levels based on your maximum heart rate (HRmax), each targeting different fitness goals. They were made popular by sports scientists, trainers, and heart rate monitor companies in the 1980s and 1990s. The five zones are as follows:

A method that’s often preferred by elite athletes is the Karvonen method, which is a way to figure out how hard you should exercise based on your own heart rather than general numbers.

It uses your resting heart rate and your maximum heart rate to provide your heart rate reserve — the range your heart can work within. Then it calculates training zones as a percentage of that personal range. The American College of Sports Medicine defines percentages of heart rate reserve as follows:

• Very light: <30
• Light: 30–39
• Moderate: 40–59
• Vigorous: 60–89
• Near-maximal to maximal: ≥90

Your maximum heart rate is the highest number of times your heart can beat per minute during intense exercise. The most common way to estimate it is with this formula: 220 minus your age. The American Heart Association provides a predicted maximum heart rate for each age group:

However, it’s worth noting that these predictions are based on age alone. In reality, maximum heart rate is based on many other factors, so these figures are only a rough estimate.

Is there a magic fat-burning heart rate zone?

Zone 2, 60–70% of your HRMax, is often called the fat-burning heart rate. The idea is that your body burns a higher percentage of fat for fuel during low-intensity workouts.

This theory comes from early exercise physiology studies that measured how the body uses fat versus carbs at different intensity levels. They found that with around 60–70% of maximum effort, the body could burn fat efficiently without needing quick energy from carbs. For example, a 2003 study found that maximal fat oxidation occurred at 63 % VO(2)max.

One study looked at how the ‘fat-burning zone’ compares to the aerobic zone (moderate exercise intensity) in fit runners. It found that the fat-burning rate peaks at around 60–80% of a person’s heart rate, and this overlaps a lot with aerobic training, so with the right workout intensity, you can improve both fat-burning and fitness at the same time.

A 2020 review explains that fat is an important source of energy during exercise, especially during low and moderate intensity exercise. Researchers share that fat burning peaks around 60–65% of your max effort but above around 75% of your max, your body starts using more carbs instead of fat for energy.

However, while you may burn more fat proportionally in zone 2, high-intensity exercises can still burn more total calories and fat overall. Workouts in zone 2 are by no means the only way to shed pounds.

Practical tips for weight loss

A calorie deficit is the most important factor when it comes to weight loss, and you may find high-intensity workouts are a more convenient way for you to achieve that deficit. It’s different for everyone. Professor Frank Joseph, founder of Dr Frank’s Weight Loss Clinic, shares that:

People living with obesity or who are overweight will often find it easier and more beneficial to do more moderate-intensity exercise, which allows them to reach a more moderate heart rate increase and sustain it for a longer period of time.

Frank Joseph

He also discusses the limitations of targeting a specific heart rate:

“The greatest limitation is keeping track of your heart rate in real-time. This is much better nowadays with wearable technology, but even that has its limitations. It is also not always easy to focus on your workout while you’re trying to constantly keep within a target heart rate zone.”

As a physical therapist, I’ve worked with thousands of clients trying to lose weight. I always told them the same thing: a calorie deficit matters most for fat loss.

Here are my top tips to help you lose fat and boost your overall health.

1. Focus on nutritious, balanced meals high in protein, fiber, and whole foods.
2. Combine strength and cardio training to burn calories while maintaining muscle mass.
3. Track your progress and adjust your diet as you go, if needed.

Choosing your own exercise intensity

Helping people find the right exercise intensity was the bread and butter of my work as a physical therapist. You can keep an eye on how hard you’re working using simple tools like the talk test or a heart rate monitor. When describing the talk test, the CDC breaks down moderate and vigorous exercise intensity:

Training across different heart rate zones can offer incredible benefits, like improving endurance and increasing cardiovascular fitness and heart health. That said, the best physical activity is something you enjoy and can stick with. And if you’re starting a new exercise routine, especially if you have any health concerns, it’s always important to speak to a healthcare professional.

The bottom line

There’s no secret fat-burning heart rate, but understanding how your body uses energy at different intensities can help you achieve your goals. While zone 2 can support fat-burning and build endurance, higher-intensity workouts might better suit your lifestyle and help you burn more calories overall.

It all comes down to your personal preference and fitness level. Don’t get too caught up with your exact heart rate — what matters most is keeping active in a way that feels sustainable for you.