Is LISS or HIIT Better For Fat Loss?

 

Have you been asking yourself lately which form of cardio is the best for fat loss? Specifically, is LISS or HIIT better for fat loss? Well today I'll go in depth and answer many common questions. 

Charles Poliquin -  One of the greatest strength coaches of all time frequently mentioned throughout his coaching career that "Cardio makes you fat" and preferred weight training as a means for fat loss or High Intensity Interval Training otherwise known as HIIT.

 Charles is a world-renowned strength coach to multiple Olympic gold medalists, founder of the Poliquin Institute of Certified Practitioners (PICP Program), and author of 8 highly recommended books(I am very fortunate to own 6 of the 8 books in my library as they are challenging to find being out of production for several years).

 

When I first started working out, I probably wouldn't have believed a statement like this from Charles Poliquin. Like the majority of gym goers today, I believed that low intensity cardio was the quickest and most efficient way to burn fat, however nearly 2 decades later and a ton of experience with physique development and athletic performance, I agree with him... to an extent, which I will explain further below.

 

LISS vs HIIT for Fat Loss: Which Workout Style Reigns Supreme?

 

To keep all this structured I will break this article down into 2 parts

 

• Part 1 will discuss what Low-Intensity Steady State(or LISS) cardio is, its preferred energy pathway, and its pros and cons for an athlete or bodybuilder. I will also give some examples workouts that you can use as part of your LISS programming

• Part 2 will discuss what High-Intensity Interval Training(or HIIT) cardio is, its preferred energy pathway, and its pros and cons for an athlete or bodybuilder. I will also give some examples workouts that you can use as part of your HIIT programming

 

PART 1

 

 

What is Low Intensity Steady State (LISS)?

 

• LISS involves sustained periods of low to moderate-intensity exercise at a steady pace.
• It is a low-impact workout style that can be beneficial for cardiovascular health and fat loss.
• Low-Intensity Steady State cardio targets the oxidative aerobic system and might be easier for a novice gym user. 
• You can easily maintain a consistent speed, level of intensity, or work rate during an exercise session making it easy to monitor  

What Is the fat burning science behind LISS?

 

When exercising at lower intensities or in the absence of glucose, the body burns stored fat for energy. This fat, known as "triglycerides," is broken down into fatty acids, which are used to produce acetyl coenzyme A and then ATP.

This energy-producing system takes time to start, but once it's running, it's highly sustainable. However, this type of exercise can be boring due to its repetitive and seemingly never-ending nature.

Steady-state training aims to make the body as efficient as possible, using the least amount of oxygen and energy to perform the most work. While this is metabolically efficient, it's not ideal for fat loss or muscle building.

Additionally, low-intensity aerobic training like walking can lead to the loss of lean muscle mass over time, resulting in a decrease in resting metabolic rate and fewer calories burned. 

 

What are the pro's and con's of using LISS for burning fat?

 

Pro's

• Improve aerobic metabolism by increasing mitochondrial density in the slow twitch type I muscle fibers. 
• Increases cardiac efficiency; Allowing you to perform more work in a shorter time with less strain on the heart.
• Helps preserve muscle glycogen to be used for higher-intensity exercise, with less metabolic waste and cellular damage than HIIT workouts while optimizing the ability to use fat as an efficient fuel source.

 

Con's

• Steady-state training may require extended periods of training time to achieve the desired level of caloric expenditure If the goal is weight loss.
• May require lengthy exercise sessions, which can increase the risk of repetitive stress injuries and be a challenge for a busy lifestyle, If the goal is to increase aerobic capacity.
• There are numerous research articles out of Finland and Australia that show endurance training as a primary source of cardiovascular work will make fast twitch fibers take on contractile properties of slow twitch fibers, thus decreasing mitochondrial density in fast twitch Type 2 fibers eventually resulting in less strength, acceleration, and power produced by your muscles. Not a good scenario for a functional athlete, powerlifter or those interested in maximising muscle for their genetic capability.

 

Examples of LISS workouts that target the oxidative aerobic system are:

 

• High rep weight training to failure with 20 to 30 reps per set. It would be wise to use multi-joint exercises such as squats, deadlifts, chin-ups, chest presses, overhead presses, and step-ups.

 

• Tempo runs such as 1 to 3-minute bursts above the lactate threshold or the 80% heart rate zone, followed by a regular pace immediately after (below lactate intensity) for 20 minutes. Repeat 3 times if your run is one hour.

Part 2

 

 

What is High Intensity Interval Training (HIIT)?

 

• HIIT involves short bursts of high-intensity exercise followed by brief periods of rest or active recovery.
• It is a time-efficient workout style that can be adapted to various exercises and fitness levels.
• High-intensity Interval Training targets the anaerobic glycolytic system(lactic acid pathway). 

What Is the fat burning science behind HIIT?

 

HIIT Primarily targets Carbohydrates, which are metabolized from blood sugar or muscle glycogen during intense sessions to produce 2 molecules of ATP.

The byproduct pyruvate is formed, which has one of two roads. During high-intensity training when there is a lack of oxygen (anaerobic intensity), pyruvate is converted to lactate, leading to the buildup of metabolic waste products. This increases to hydrogen ions and other metabolites, causing the muscle pH to decrease. Although not dangerous, this process leads to acidosis, which can be mentally painful to push through during exercise, and the muscle loses its strength capacity, resulting in a decrease in exercise intensity.

On the other hand, during moderate training when there is enough oxygen reaching the muscles, pyruvate is turned into acetyl coenzyme A. This substance is then used to produce even more ATP, allowing for sustained exercise intensity.

 

What are the pro's and con's of using HIIT for burning fat?

 

Pro's

• Dramatically improves aerobic capacity & calorie burning in less time, making HIIT very effective when compared to high-volume, steady-state training.
• Can be an effective strategy for those who become easily distracted/bored during longer exercise sessions.
• Has been shown to improve the efficiency of the fast twitch type 2 muscle fibers to produce energy via anaerobic glycolysis, resulting in greater metabolic efficiency. The more lactate produced during the session, the greater the production of muscle-building, fat-burning hormones such as testosterone, growth hormone, and insulin-like growth factor. 
• Has been shown to increase EPOC (excess post-exercise oxygen consumption), This helps to continue burning calories hours after your session ends. Steady State Cardio does not provide this benefit.

 

Con's

• HIIT for extended periods could deplete glycogen stores and result in gluconeogenesis (The metabolic process of converting protein to produce glycogen) which will limit the amount of protein available to repair muscle tissue damaged by exercise.
• The accumulation of metabolic stress due to anaerobic metabolism results in a muscle’s inability to function. It's worth noting that prolonged mechanical stress of HIIT can increase the risk of muscle strain. 

Examples of HIIT workouts that target the anaerobic glycolytic system are:

 

• Sprints on an assault bike of 8 seconds all-out followed by 12 seconds rest. Repeat this up to 60 times for a total of 20 minutes. This is a recommended approach for a beginner.

 

• Back when I used to sprint competitively, a method I used to love using was descending sprints of 400, 300, 200, and 100 meters. Rest around 4 minutes after the 400m sprint, 3 minutes after the 300m sprint, 2 minutes after the 200m sprint, and 1 minute after the final 100m sprint. A well-conditioned athlete could repeat this from the start(400m) or reverse it back starting with 100m and finishing at 400m. A total of 2 cycles is enough.

 

• A more functional method I use nowadays is the prowler sled, alternating between a sled push and a sled pull. For example, I'll push the sled 20 meters and pull it back 20 meters. The total time it should take you is about 30 seconds. That's considered 1 set or 1 cycle. Rest for 2-3 minutes and repeat up to 5 times. This is my personal favourite for shredding fat quickly, maintaining muscle mass and strength, activating the fast twitch type 2 fibers, and providing a total body lactate stimulus which helps produce higher concentrations of Testosterone, Growth Hormone, and IGF levels naturally in the body.

Key differences between HIIT and LISS

 

• HIIT is high-intensity with short bursts of exercise, while LISS is low-intensity with sustained periods of exercise.
• HIIT is time-efficient, while LISS requires longer workout sessions.

 

 Picture above: Comparison between a long distance runner primarily using the aerobic energy pathway(left) and a short distance runner primarily using the anaerobic energy pathway(right).

 

 My personal thoughts on both forms of cardio.

 

Nearly a decade ago, when I was actively competing as a bodybuilder, I decided to test out both cardio systems during my prep. What I found was that the LISS approach, which involved 7 hours of cardio a week (1 hour per day), left me feeling drained. I particularly noticed a deflation in my legs from excessive use of the cross trainer or incline treadmill. My body became so efficient at burning calories during this form of cardio that I had to increase my daily time by 5 minutes each week. I also observed that my type 1 muscle fibers were becoming more efficient than my type 2 fibers, likely due to the endurance-style cardio I was consistently doing. This shift was negatively impacting my weight training 

By following the HIIT Approach, I was able to decrease my weekly exercise volume by 66% (20 minutes of HIIT a day compared to 1 hour of steady-state cardio). Additionally, I became more neurologically efficient on my weight training days, due  to the increased use of type 2 fibers. This resulted in improved strength and the ability to lift heavier weights, ultimately leading to fuller and rounder muscles. The convenience of finishing my workout in just 20 minutes was mentally satisfying, especially during weeks of low-calorie intake. 

"The outcome? In the early part of the year, using the LISS approach, I achieved a top 5 placement at the RIBBF Irish Bodybuilding Championships. Later in the year, at the Mr. Ireland National Bodybuilding Championships, I placed 1st and won the Junior Class by utilizing the HIIT approach. The competition in both events was fierce, with everyone performing at their best, so it's possible that my choice in cardio method made a significant difference." 

 

Putting it all together

 

Consistency, Patience, and a Balanced Approach to Fat Loss

• Consistency and patience are key to achieving fat loss and improving overall fitness.
• A balanced approach that incorporates both HIIT and LISS, as well as other forms of exercise and healthy habits, can help to achieve optimal results.

Choosing the Right Workout Style for Your Lifestyle and Goals

• Choosing the right workout style depends on individual goals, fitness levels, and lifestyles.
• It is important to consider the benefits and limitations of both HIIT and LISS, as well as other forms of exercise, when creating an effective workout plan.

 

The Physique Protocol Pro Tip

In my experience, many individuals trying to lose fat tend to rely solely on low-intensity or steady-state cardio for their cardiovascular exercise. The problem with this approach is that your body is highly intelligent and adaptive to external stresses, therefore after 6-8 weeks your body has maximally adapted to low-intensity cardiovascular work. At this point, it's crucial to change to high-intensity cardio to create a new adaptation within the body for a further 6- 8 weeks.

After years of competitive training, I have found that incorporating both low and high-intensity cardio is the most effective way to achieve single-digit body fat while also building strength, muscle, and overall athleticism. It's important to keep the body guessing and constantly adapting to new challenges for optimal results.