Is there an ideal heart rate zone for burning fat? The experts answer (2024)

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  • Which is the ideal heart rate zone for fat loss?
  • The key rule for losing body fat

Heart rate zones are a useful thing to understand if you're trying to achieve certain goals with your workouts. With wearable fitness trackers being all the rage, it's easier than ever to monitor how fast your heart is beating – but if the only thing you know about your heart rate is that is gets very high, very quickly as soon as you put on your gym gear, you might want to listen and learn...

If your aim for exercise is fat loss, you'll probably be wanting to know if there's an optimum heart rate zone for burning fat. And, well, it's a confusing one. Because technically there is a heart rate zone where your body burns more fat, but the speed at which it burns makes it a little more complicated than that.

Also, it's important to note: before embarking on any weight loss journey a) think about why you're doing it (is it to lower your risk of certain diseases, or because you're struggling with poor body image? And if you are you struggling with poor body image, could you use mental health support?) and b) it's always best and safest to chat with your GP or a qualified professional before making any drastic changes to your routine.

What are the five heart rate zones?

First, what exactly are they and how can they help? 'Being aware of your heart rate zones can benefit health and fat loss because it allows you to optimise your exercise and training intensity to achieve specific goals. They provide a structured training approach that considers individual fitness levels and your goals,' says PT and wellness coach Rachael Sacerdoti.

'When you exercise, different heart rate zones represent different intensity levels, each with its own benefits. By understanding these zones, you can tailor your workouts to suit your specific objectives, and they are crucial for maximising the effectiveness of your workouts and achieving your fat loss goals.'

Now, here's to explain those different types.

'Heart rate zones are typically split into five training zones, which can be based off your maximal heart rate (HR max),' says fitness coach and health expert Thomas Roberts MSc.

They are as follows:

  • Zone 1 (very light exercise): 50-60% of HR max, able to maintain this for long periods of time, only fat burned as fuel, typically for warm ups, recovery or cool downs.
  • Zone 2 (light exercise): 60-70% HR max, sometimes called conversation pace (with the idea being you can still chat as your exercise). This sees a mix of fats and carbohydrate used as fuel (but majority from fat), used for longer, steady activity, low energy expenditure per hour, not time efficient, good for marathon training.
  • Zone 3 (moderate exercise): 70-80% HR max, carbohydrate and fat burned 50/50 as fuel sources, great for building strong aerobic base.
  • Zone 4 (hard/threshold exercise): 80-90% HR max, majority of fuelling comes from carbohydrate and between 10-45% comes from fat sources, time efficient, could be a tough 30 minute session or used for longer interval sessions
  • Zone 5 (maximal exercise): 90-100% HR max, high intensity interval training, should be a 9/10 in terms of self perceived exertion, fuelling all comes from carbohydrates, very time efficient, can cause muscle damage and soreness, can lead to an increased amount of muscle mass.

How to calculate your maximum heart rate

In order to work out which heart rate zone you're working in, you'll need to know your maximum heart rate. A simplified way of working this out, the expert explains, is to do the following calculation:

207 - 0.7 x (age) = HR maximum

So if you were 28 years old, for example, you would calculate 0.7 x 28 (which is 19.6), and take that away from 207, making 187.4 - that would be your maximal heart rate.

Now you know this, you can work out your training zones, although Roberts warns there are 'limitations to this as it will vary between individuals'. If you wanted to calculate your true, personal heart rate maximal you would need to do a 'maximal test' under medical supervision.

Is there an ideal heart rate zone for burning fat? The experts answer (1)

        Which is the ideal heart rate zone for fat loss?

        The body burns fat as fuel for exercise at lower intensities (in heart rate zones 1 and 2), whereas it burns carbohydrates as fuel at higher intensities (zones 4 and 5). This, the expert explains, is because 'fat takes longer to burn and use as energy in comparison to carbohydrates'.

        'As there is a higher demand for energy at high exercise intensities, we use carbohydrates because the body produces energy from these very quickly,' he adds. 'The way I like to explain it is like gears in a car; the higher the gear, the greater the fuel source needed, meaning the speed at which it is required increases, and fats alone cannot meet this higher demand for energy.'

        Knowing this, it would make sense to assume that working in heart rate zones 1 and 2 (when you're working anywhere between 50% and 70% of your maximum exertion) is best for burning fat. But that's not necessarily the case.

        'At zone 1, as a percentage you would be burning the most fat, and at zone 5 you would be burning the least amount of fat as a fuel source [because you're burning carbohydrates instead]. However, this does not mean that zone 1 is the most effective for weight loss,' Robert tells us.

        'You would need to work out far longer within low intensity zones 1 and 2 to burn the same amount of calories as you do at a higher intensity,' the expert explains. And ultimately, it's the number of calories you burn which determines how much fat/weight you lose.

        'As a very simple example, not to be taken literally, if you walked for one hour in zone 2 you may burn around 400 kcal, and 90% of that may be through fat sources. But if you ran for one hour in zone 4 you may burn 800 kcal, of which around 20% from fat sources. But overall you would have burned a higher amount of calories in your run than you would in your walk,' Thomas explains. Got it.

        If you're having trouble keeping track of your heart rate zones, Sacerdoti suggests utilising a wearable device with a built-in heart rate monitors or smartphone applications, like a Fitbit.

        'They provide real-time tracking, aiding you in adjusting your intensity. Not only that, but they can also boost your motivation, making it easier for you to stay engaged with your workout routine. Moreover, tracking your heart rate during exercise can ensure you're working more efficiently within the appropriate zone, preventing under or overexertion.'

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        The key rule for losing body fat

        Sadly, there's no way to 'hack' the system. 'When trying to lose body fat, the only way to do that is through a calorie deficit,' the health advisor says. 'This means eating fewer calories than you are burning. Every diet works on this same principle, but different diets work for different people and the one you can be most consistent with is the one you will succeed with.'

        Diet aside, the best advice Thomas has for burning fat is to ensure your workout includes a range of heart rate zones. 'Essentially the more time you spend within a zone the more efficient you get working within that zone,' the expert tells us. 'For the best outcome, work in a mix of heart rate zones to provide variety.'

        And emphasising the importance of balance, Sacerdoti adds, 'By staying in tune with your heart rate zones during exercise, you can fine-tune your workouts, optimise fat loss, and achieve your fitness goals more efficiently. But remember to mix up your routine and keep it fun. While it's important to set goals, exercising for your overall wellbeing, without always focusing on your heart rate, can hugely benefit your mind and body.'

        Thomas Roberts MSc was a health adviser at Bupa Health Clinics, specialising in exercise physiology, at the time of interview.

        Is there an ideal heart rate zone for burning fat? The experts answer (7)

        Catriona Harvey-Jenner

        Features Editor

        Cat is Cosmopolitan UK's features editor covering women's issues, health and current affairs. news, features and health. The route to her heart is a simple combination of pasta and cheese (somewhat ironic considering the whole health writing thing), and she finds it difficult to commit to TV series so currently has about 14 different ones on the go.

        Is there an ideal heart rate zone for burning fat? The experts answer (2024)

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