When it comes to losing fat efficiently, many people focus on what they eat and how they move – which is absolutely the right thing to do.
Fat loss will occur over time if you consume fewer calories than you require (calorie deficit), but I’m hearing a lot of noise recently about heart rate zones and exercising within a ‘fat burning zone’ so I wanted to explain this properly, in a way everyone will understand.
What are Heart Rate Zones?
Heart rate zones are ranges that reflect the intensity of your exercise. They are typically calculated as a percentage of your maximum heart rate (MHR), which is roughly estimated as 220 minus your age. Each zone corresponds to a different level of effort, and different zones are more effective for different fitness goals.
Here’s a simple breakdown:
Zone 1: very light activity
Zone 1: very light activity
Zone 2: light activity
Zone 2: light activity
Zone 3: Moderate activity
Zone 3: Moderate activity
Zone 4: Hard activity
Zone 4: Hard activity
Zone 5: Maximum effort
Zone 5: Maximum effort
What it all means...
However...
How to Calculate Your Heart Rate Zones
You can easily calculate your zones with the formula:
Maximum Heart Rate (MHR) = 220 – Your Age
For example, if you’re 40, your MHR is roughly 180 beats per minute (bpm). Zone 2 would be 60-70% of that, which equals 108-126 bpm.
Why Zone 2 is often portrayed as ‘key’ for fat loss
You might have heard the term “fat-burning zone” before, and it refers to Zone 2, where you are working at 60-70% of your maximum heart rate. It’s called the ‘fat burning zone’ because at this level of intensity, your body is still able to use oxygen to convert fat and carbohydrates into energy.
At rest, we typically have enough oxygen available for ‘aerobic’ (with oxygen) energy production to occur – this is the body’s preferred energy system. As exercise intensity increases, so does the demand for energy, so the body begins to use its ‘anaerobic’ (without oxygen) energy production system, which can only use carbohydrates (glucose) to produce energy. The body cannot utilise fat stores when producing energy anaerobically.
Low intensity exercise = Aerobic energy production (with oxygen) = uses FATS and CARBS
High intensity exercise = Anaerobic energy production (without oxygen) = uses CARBS only
Based on the above, you would be right to think that it is possible to reduce body fat without exhausting yourself with high-intensity workouts every day, however, before you switch your workout regime to include Zone 2 activities exclusively (hint: don’t do this!), please consider the following reasons why working out within Zone 2 exclusively may not be the best thing for you…
- You will need to exercise in Zone 2 for a much longer period of time to burn the same number of calories as you would during shorter periods of higher intensity exercise. It can therefore be viewed as a ‘less efficient’ way to exercise – it takes much longer.
- If fat loss is the goal, then calories in must still be less than calories out, regardless of the Heart Rate Zone you stick to.
- There are huge cardiovascular (heart and lung), physiological (muscle and bone), hormonal, psychological and wellbeing benefits to working out at higher levels of intensity – staying within Zone 2 will not deliver the same overall health and fitness benefits.
- We haven’t even covered any of the benefits of weight lifting / resistance training here; everyone should be doing this type of training, even if it means pushing yourself out of Zone 2!
- It’s easy to let heart rate monitoring become a distraction – your body is an expert at generating the energy it needs, when it needs it, so don’t over-engineer it!
- Any exercise is better than no exercise, so do what you love!
Training Structures
Once you know your heart rate zones, you can structure your workouts to target the different zones and intensity levels.
If you’re aiming to burn fat, incorporate 30-60 minutes of steady-state cardio, like walking, cycling, or swimming, in Zone 2. This will ensure your body burns fat as its primary fuel source. This doesn’t need to be in the gym! This could be 3 x brisk walks per day, allowing the time you have in the gym to be dedicated to strength / CV fitness activities.
While Zone 2 is great for fat loss, you can also mix in high-intensity interval training (HIIT). By alternating between Zone 2 and short bursts of Zones 4 and 5, you can increase your calorie burn and boost your metabolism. HIIT has a lasting effect on fat-burning, even after your workout.
To see results, it’s important to be consistent with your workouts. Aim for at least 3-5 sessions a week in Zone 2, supplemented with higher-intensity interval training once or twice a week.
Tools to Help You Track
You don’t need fancy gadgets to start using heart rate training for fat loss, but a heart rate monitor or smartwatch can be incredibly helpful. Many fitness trackers have built-in features that calculate your zones based on your age, or you can manually track it by checking your pulse periodically during exercise.
The Bigger Picture
While exercising in the right heart rate zones can certainly accelerate fat loss, it’s important to remember that nutrition, sleep, and overall lifestyle also play major roles in reaching your goals. Keeping your body in a slight calorie deficit (burning more than you consume) is essential for fat loss, no matter what heart rate zone you’re working in.
Finally, don’t forget the mental aspect – patience and consistency are key. Fat loss doesn’t happen overnight, but by regularly incorporating heart rate-based training, you’ll be well on your way to seeing results.
