HIIT vs LISS

Which Is Best For Fat Loss And Fitness

The debate about HIIT vs LISS cardio can get heated. Some scream about intervals while others shout about steady state.

But how do you know what kind of cardio is best for you? After all, the last thing you want is to waste your time doing something that doesn’t get results.

For that reason, my goal is to have a rational conversation about cardio. And help you figure out how to get better results without wasted effort.

HIIT vs LISS

Exercise Intensity 101

Before we dive into comparing HIIT vs LISS, let me explain a little bit about exercise intensity.

First, high intensity and low intensity are defined by your heart rate. The more times your heart beats per minute (bpm), the higher the intensity.

Furthermore, exercise intensity is divided into 5 zones. Each zone represents a percentage of your maximum heart rate and corresponds to a particular training benefit.

Heart Rate Training Zones

Figure 1. Heart rate training zones.

As you can see in Figure 1, your max heart rate decreases with age. And you can estimate your maximum by subtracting your age from 220.

For example, if you’re 30 years old your max heart rate is around 190 beats per minute (220 – 30). From there, each zone is a percentage of 190 bpm.

With this information, you can adjust your training to get the results you want. Now let’s get into what kind of training is best for fat loss and overall fitness.

HIIT vs LISS

HIIT (High Intensity Interval Training) consists of short bursts of effort where you get close to your max heart rate. Followed by slower recovery periods to get your heart rate back down. Whereas LISS (Low Intensity Steady State) is a constant pace at 50-70% of your max heart rate.

HIIT vs LISS for Fitness

Figure 2. HIIT vs LISS comparison of heart rate and duration. Example shows 20 minutes of HIIT with 5 intervals of 1 minute on, 2 minutes off. Compared to 30 minutes of steady state.

Generally, HIIT workouts are shorter in duration due to the taxing nature of max-effort exercise. On the other hand, LISS workouts can be sustained for long durations because they don’t take a big toll on the body.

One advantage of HIIT is that your average heart rate is higher compared to LISS. As indicated by the dashed lines in Figure 2.

And a higher average heart rate means you burn more calories. In fact, HIIT burns 40-60% more calories per minute than LISS.

HIIT vs LISS Calories Burned Per Minute

Figure 3. Calories burned during exercise is directly proportional to the intensity of the exercise.

As an example, let’s compare 20 minutes of HIIT with 30 minutes of LISS. In this case, both workouts burn 300 calories (20 minutes x 15 calories per minute = 300 calories and 30 minutes x 10 calories per minute = 300 calories).

If you stopped here, you might conclude that HIIT is superior to LISS because you burn the same number of calories in less time. But to see which is really better, we need to look closer.

HIIT vs LISS for Fat Loss

While it’s true that HIIT burns more calories than LISS, it’s important to know where those calories come from. Specifically, if you’re burning carbs or fat.

You see, higher intensity exercise burns more calories from carbs. While lower intensity exercise burns more calories from fat.

Fat vs Carbs Burned During Exercise

Figure 4. As exercise intensity increases, the calories burned from fat decrease.

Continuing our example, the HIIT workout only burns 90 calories from fat (30% of 300 calories). But the LISS workout burns 135 calories from fat (45% of 300 calories).

When calories per workout are the same, LISS burns about 50% more fat than HIIT.

If you graph calories burned from fat it’s easy to see how LISS burns more fat. At around 70% of your max heart rate, you hit the sweet spot for burning the highest amount of body fat per minute.

HIIT vs LISS Calories Burned From Fat

Figure 5. The curve resulting from multiplying calories burned per minute (Figure 3) by the % calories from fat (Figure 4).

In addition to burning the maximum fat calories per minute, LISS also lasts for 30 minutes or more. Altogether, this means LISS has far more fat-burning potential than HIIT.

To find your target heart rate for max fat burning, use the table below. Simply find the age nearest yours at the top and follow it down to the blue row to get your heart rate.

Or you can use my Cardio Calories Burned Calculator below.

Heart Rate Zones Table

Table 1. Estimated heart rates per training zone by age.

What About EPOC?

But hold on, we’re not done yet! Proponents of HIIT argue that you burn more calories after high intensity training. This is due to EPOC (Excess Post-Exercise Oxygen Consumption). Also called the after-burn effect.

Basically, you can’t get enough oxygen to replace what you use during intense exercise. And that creates an oxygen deficit.

With an oxygen deficit, your respiratory rate increases for a while after exercise, which burns calories. Since EPOC is greater after HIIT than LISS, the thought is that you burn more calories while recovering.

HIIT vs LISS EPOC

Figure 6. Effect of Excess Post-Exercise Oxygen Consumption for HIIT vs LISS.

However, LISS consumes more oxygen during exercise compared to HIIT. So the 24-hour oxygen consumption (total green area) is pretty much the same for HIIT vs LISS.

Indeed multiple studies show that the difference in 24-hour energy expenditure between HIIT and LISS is not statistically significant1,2,3,4. That means greater EPOC doesn’t necessarily mean more fat burning.

In summary, HIIT burns more calories per minute. But LISS generally burns more fat per minute. And the longer duration means you can burn significantly more fat with LISS.

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HIIT vs LISS for Fitness

For some people, the goal of cardio isn’t to burn as much fat as possible. You might use it to increase performance or train for a sport.

In that case, the assessment of HIIT vs LISS is completely different. So let’s find out which is better for overall fitness.

One way to assess fitness is by measuring power during sprint activities like running or cycling (peak performance). And another is measuring how fast your heart rate returns to normal after sprints (heart rate recovery).

HIIT vs LISS For Fitness

Figure 7. Percent improvement in peak performance and heart rate recovery for HIIT vs LISS protocols. Adapted from TL Stoggle et. al.5

In a 2017 study, researchers concluded that HIIT workouts resulted in a greater increase in peak performance. As well as a much larger improvement in heart rate recovery compared to LISS.

In addition, during HIIT workouts your average heart rate is near the anaerobic threshold. This is the line between medium intensity (aerobic) and high intensity (anaerobic).

In other words, it’s like running at your fastest mile pace – where you can’t push any harder without taking a break.

Effect of HIIT on Heart Rate Zones

Figure 8. Effect of HIIT on Heart Rate Zones

By training at the anaerobic threshold, you increase your ability to sustain higher heart rates for longer. Effectively moving the anaerobic threshold higher.

At the same time, regular bouts of max-effort actually increase your maximum heart rate. For example, it’s possible for a 30-year-old to have a max heart rate of 200 bpm (equivalent to that of a 20-year-old). Thereby bumping up all your heart rate zones.

Most importantly, your fat burning zone moves up too. That means you can do LISS at a higher heart rate and burn even more calories from fat!

In summary, HIIT is more effective than LISS for improving overall fitness. And it can even help you burn more fat during LISS.

Which One Should You Do?

At the end of the day, the HIIT vs LISS debate doesn’t have an “always” or “never” conclusion. Often, the best solution is a combination of both HIIT and LISS.

How much HIIT or LISS you do depends on your goals as well as your personal preference. It’s important to find the form of exercise you actually enjoy so you’ll do it consistently.

Fat Burning Routine

For maximum fat loss, you should focus on LISS. While you don’t really need HIIT to maximize fat loss, you can include it if you like more challenging workouts or to mix things up.

  • Aim for at least 150 minutes per week

  • Split it up into 3 to 6 LISS sessions, 30 to 60 minutes each

  • Target around 70% of your max HR

  • Examples: fast walking, slow jogging, cycling

  • Limit HIIT to 0 to 2 sessions per week

Fitness Routine

For optimal fitness, a mix of HIIT and LISS works best. Before doing HIIT workouts, make sure you’re healthy enough for max effort bouts. And include a 5-10 minute warm-up and cool down at 70% max HR.

  • Aim for at least 150 minutes per week

  • Split it up into 2 to 3 HIIT sessions, 10 to 20 minutes each

  • Target 90-100% max HR during intervals, with 30 sec to 3 min recovery periods

  • Examples: sprint/walk, row/rest, circuit training

  • Do LISS on days you don’t do HIIT

What About Resistance Training?

Resistance training consists of short bouts of anaerobic exercise separated by 30 seconds to 3 minutes of recovery. So, by definition, resistance training is a HIIT workout! At least when you’re training hard enough to spike your heart rate during each set.

Not only does weight training build muscle, but it also burns a lot of calories and improves overall fitness. However, as with HIIT cardio, lifting weights is very taxing on your nervous system

For that reason, it’s probably not a good idea to do a lot of HIIT cardio when you’re resistance training multiple days per week. Instead, save that intensity for the weight room and use LISS to burn fat.

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HIIT vs LISS Calculator

If you’re still not sure what your heart rate should be during your cardio sessions, don’t worry. I’ve got you covered with my Calorie Burn Calculator.

With this calculator, you’ll see your target heart rate for each training zone. As well as how many total calories and calories from fat you’ll burn.

calorie burn calculator

Enter the information below to see your heart rate, calories burned, and fat burned. Easily adjust your workout to maximize fat burning!

HIIT vs LISS Final Thoughts

Both HIIT and LISS have their benefits and each can be a valuable tool in your cardio toolbox.

LISS is best suited to burning fat without stressing your body too much. While HIIT is great for improving fitness, or when you’re short on time.

Once again, the choice between HIIT and LISS really depends on your goals and personal preference. I’ll leave you with this final graphic summarizing the pros and cons of each so you can decide which is best for you.

HIIT vs LISS Comparison

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