HIIT vs. LISS: Which is Better for Fat Loss?

When it comes to cardio for fat loss, two popular methods dominate the fitness landscape: High-Intensity Interval Training (HIIT) and Low-Intensity Steady-State (LISS) cardio. Both have their loyal fanbases, but which is truly better for fat loss and overall health? To answer this, we’ll explore the science, benefits, drawbacks, and practical recommendations for both approaches, as well as taking a look at the use of heart rate zones to help plan your workout intensity. 

Understanding HIIT and LISS. 

What is HIIT?

High-Intensity Interval Training (HIIT) involves alternating between short bursts of intense exercise and periods of low-intensity recovery or rest. For example, a HIIT workout might include 30 seconds of sprinting followed by 90 seconds of walking, repeated for 20 minutes. These workouts are typically shorter, lasting anywhere from 15 to 30 minutes.

What is LISS?

Low-Intensity Steady-State (LISS) cardio, on the other hand, involves maintaining a steady, moderate pace over a longer duration. Common examples include walking, jogging, cycling, or swimming at a consistent speed for 30-60 minutes or more. The intensity remains low enough to sustain the activity comfortably.

The Science of Fat Loss: HIIT vs. LISS 

Fat Burning and Calories

Both HIIT and LISS can aid in fat loss, but they work in different ways:

• HIIT: HIIT is renowned for its afterburn effect, scientifically known as Excess Post-Exercise Oxygen Consumption (EPOC) [1]. After a HIIT workout, your body continues to burn calories at an elevated rate for hours as it works to recover. This phenomenon means HIIT can lead to greater overall calorie burn in less time compared to LISS.

• LISS: LISS relies on the body’s ability to utilise fat as a primary energy source during low-intensity exercise [2]. While the immediate fat-burning percentage may be higher during LISS, the total caloric expenditure is often lower compared to a well-designed HIIT session.

Hormonal Impact

• HIIT: HIIT stimulates the release of hormones like epinephrine and norepinephrine, which enhance fat breakdown [3]. Additionally, HIIT increases insulin sensitivity, making it easier for your body to process and store nutrients efficiently.

• LISS: LISS is less intense, so its hormonal impact is milder. However, it can help reduce cortisol levels (stress hormone) over time, which is beneficial for individuals dealing with stress-induced fat storage.

Muscle Preservation

• HIIT: High-intensity workouts can stimulate muscle growth and strength due to the anaerobic nature of the activity, which engages fast-twitch muscle fibres. This makes HIIT particularly appealing for individuals looking to retain or build muscle while losing fat.

• LISS: LISS primarily engages slow-twitch muscle fibres and has minimal impact on muscle growth. However, it’s easier to perform for longer durations, leading to steady caloric expenditure without overtaxing the body.

The Benefits 

The Benefits of HIIT

1. Time Efficiency

HIIT workouts are short and effective, making them ideal for individuals with busy schedules.

2. Increased Metabolic Rate

The EPOC effect ensures that your body burns calories even after the workout ends.

3. Improved Cardiovascular Health

HIIT improves heart health and VO2 max (a measure of aerobic capacity) in less time compared to LISS.

4. Versatility

HIIT can be performed with various exercises—sprints, cycling, bodyweight moves, or even swimming.

The Benefits of LISS 

1. Low Impact

LISS is gentle on the joints and suitable for individuals of all fitness levels, including beginners or those recovering from injuries.

2. Stress Relief

The steady nature of LISS can have meditative qualities, reducing stress and improving mental well-being.

3. Accessibility

No special equipment or advanced fitness level is required. A simple walk or jog suffices.

4. Endurance Building

LISS enhances aerobic capacity and stamina, laying a solid foundation for overall fitness.

The Pitfalls 

The Pitfalls of HIIT

1. Risk of Injury

The intense nature of HIIT increases the risk of injuries, particularly for beginners or individuals with poor form.

2. Recovery Demands

HIIT places significant stress on the body, requiring longer recovery periods. Overdoing HIIT can lead to burnout or overtraining.

3. Not Beginner-Friendly
4. The high intensity can feel intimidating or overwhelming for those new to exercise.

The Pitfalls of LISS

1. Time Commitment

LISS requires longer workout durations, which may not be feasible for individuals with tight schedules.

2. Plateau Potential

Because LISS is less intense, the body adapts quickly, potentially leading to diminishing returns if progression isn’t incorporated.

3. Lower Caloric Burn

In a given amount of time, LISS burns fewer calories compared to HIIT.

Getting Started: Recommendations for Beginners

Starting with HIIT

Ease into Intensity

• Begin with a 1:3 work-to-rest ratio. For example, sprint for 15 seconds, then walk for 45 seconds. Repeat for 10-15 minutes.

• Choose Simple Movements

Focus on exercises like sprinting, cycling, or bodyweight movements (e.g., jumping jacks) that don’t require complex skills.

• Limit Sessions

Start with 1-2 sessions per week to avoid overtraining and monitor your body’s response.

Example HIIT Routine for Beginners:

• Warm-up: 5 minutes brisk walking or light jogging
• 15 seconds of sprinting
• 45 seconds of walking
• Repeat for 10-15 minutes
• Cool-down: 5 minutes of walking and stretching

Starting with LISS

• Pick an Activity You Enjoy

Walking, cycling, or swimming are excellent low-intensity options for beginners.

• Start with 20-30 Minutes

Gradually increase the duration as your fitness improves.

• Monitor Your Heart Rate

Aim for 50-65% of your maximum heart rate. A simple rule: you should be able to hold a conversation while exercising.

Example LISS Routine for Beginners:

• Warm-up: 5 minutes of light walking
• Walk at a steady pace for 20-30 minutes
• Cool-down: 5 minutes of slow walking and stretching

The Role of Heart Rate Monitoring in HIIT and LISS Workouts

Heart rate monitoring is a powerful tool that can elevate your High-Intensity Interval Training (HIIT) and Low-Intensity Steady-State (LISS) workouts. By providing real-time feedback on your heart’s performance, these devices help ensure you’re exercising at the right intensity to achieve your fitness goals efficiently and safely.

Understanding Heart Rate Zones

To make the most of heart rate monitoring, it’s essential to understand the heart rate zones, which are percentages of your maximum heart rate (HRmax) [4]. Your HRmax can be estimated using the formula:

HRmax = 220 – Age

Heart rate zones are typically divided as follows:

• Zone 1: Very Light (50-60% of HRmax)

Suitable for recovery or warm-ups.

• Zone 2: Light (60-70% of HRmax)

Optimal for LISS and fat burning.

• Zone 3: Moderate (70-80% of HRmax)

Improves aerobic capacity.

• Zone 4: Hard (80-90% of HRmax)

Typical of HIIT work intervals.

• Zone 5: Maximum Effort (90-100% of HRmax)

Reserved for very short, maximal bursts in advanced HIIT.

Benefits of Heart Rate Monitoring for HIIT & LISS

HIIT

1. Precise Intensity Tracking

HIIT workouts are most effective when performed in higher heart rate zones (Zone 4 and Zone 5). A heart rate monitor ensures you’re pushing yourself hard enough during work intervals and recovering adequately during rest periods.

2. Progressive Overload

Tracking your heart rate during HIIT allows you to gradually increase intensity as your fitness improves. For example, you might aim to shorten recovery periods or push closer to Zone 5 during work intervals.

3. Avoiding Overtraining

A heart rate monitor can signal when your heart rate remains elevated during rest periods or doesn’t return to baseline after a session, indicating potential overtraining or insufficient recovery.

4. Customising Intervals

By monitoring heart rate, you can personalise work and rest intervals. For instance, instead of timing rest periods, you can wait until your heart rate drops to a specific threshold (e.g., 60-65% HRmax) before starting the next interval.

LISS

1. Staying in the Fat-Burning Zone

LISS is most effective for fat loss when your heart rate remains in Zone 2 (60-70% HRmax). A monitor helps you maintain this steady intensity, ensuring you’re optimising fat metabolism without overexertion.

2. Building Aerobic Endurance

Staying in Zone 2 enhances your aerobic capacity and cardiovascular health over time. Monitoring your heart rate ensures you’re training at the right level to improve endurance.

3. Consistency and Motivation

Seeing your heart rate in real-time can serve as a motivational tool, encouraging you to maintain effort and stay within the desired range throughout your workout.

4. Detecting Improvement

Over time, as your cardiovascular fitness improves, you may notice your heart rate staying lower at the same pace. This feedback is a clear indicator of progress.

How to Use Heart Rate Monitors Effectively

• Set Your Target Zones

Determine your target heart rate zones for your workout type. For HIIT, alternate between high-intensity intervals in Zone 4-5 and recovery in Zone 2-3. For LISS, aim to stay in Zone 2 throughout the session.

• Choose the Right Device

There are several types of heart rate monitors:

• Chest Straps: Highly accurate and ideal for intense activities.
• Wrist-Based Monitors: Convenient and sufficient for most users.
• Integrated Monitors: Found in smartwatches and fitness trackers.

• Track Metrics Beyond Heart Rate

Some devices also measure calories burned, recovery time, and VO2 max, providing a comprehensive view of your fitness progress.

• Listen to Your Body

While heart rate monitors are helpful, always combine their feedback with how you feel. For instance, if your heart rate seems low but you’re struggling, you may need more rest.

Practical Examples

1. Using a Heart Rate Monitor for HIIT:

• Warm-Up: Spend 5 minutes in Zone 2 (light intensity).
• Work Interval: Sprint or cycle at 85-90% HRmax (Zone 4-5) for 30 seconds.
• Recovery Interval: Walk or pedal slowly, allowing your heart rate to drop to Zone 2-3.
• Repeat for 6-8 rounds.

2. Using a Heart Rate Monitor for LISS:

• Warm-Up: Gradually increase pace until you reach Zone 2.
• Steady Pace: Maintain 60-70% HRmax for 30-60 minutes.
• Cool-Down: Reduce intensity, staying in Zone 1 for the last 5 minutes.

HIIT vs. LISS: Which Should You Choose?

• Fat Loss Goals

If time efficiency is your priority and you’re comfortable with intense workouts, HIIT may be the better choice. However, if you prefer a gentler, less demanding approach, LISS can be equally effective when combined with a calorie-controlled diet.

• Health and Lifestyle Factors

Consider your fitness level, joint health, and stress levels. HIIT is great for maximizing calorie burn and improving anaerobic fitness, while LISS supports stress reduction and endurance.

• Combining the Two

For many, the best approach is combining both HIIT and LISS. This strategy leverages the strengths of each method while minimising their drawbacks. 

For example:

• Perform 1-2 HIIT sessions per week for metabolic benefits.
• Include 2-3 LISS sessions for active recovery and steady-state calorie burn.

Conclusion

HIIT and LISS are both effective tools for fat loss, each offering unique benefits. HIIT shines in its time efficiency and metabolic boost, while LISS excels in accessibility and stress reduction. Beginners should focus on the approach that aligns with their fitness level, schedule, and preferences. Ultimately, the best cardio routine is the one you can stick to consistently.

By understanding and applying the principles of both HIIT and LISS, you can create a balanced and sustainable fitness plan tailored to your goals. Whether you’re sprinting through intervals or enjoying a peaceful walk, the path to fat loss is yours to shape.

Please Note: The information provided in this article are the opinions and professional experience of the author and not all activities are recommended for the beginner or participants with underlying health conditions. Before following any advice or starting any fitness, health and wellbeing journey please consult with an Allied Health Professional and / or General Practitioner.

References

1. What Is EPOC? (And Why It Matters)
2. What Is LISS Cardio? A Detailed Beginner’s Guide
3. High-Intensity Intermittent Exercise and Fat Loss
4. Heart Rate Zones Explained

• Bio

Steve Irwin

Steve has spent the last 19 years in the Australian Fitness Industry as a Group Fitness Instructor, 1-1 Coach, State Manager, Business Owner and is currently an Educator for the Australian Institute of Fitness. A lifelong fitness enthusiast he started his working life in the Military which guided him into the fitness industry where his passion for helping others on their health and fitness journey has been realised. Steve believes that for anyone thinking about getting fit or healthy they should “just get started” as “doing something is better than doing nothing”.