Fitness Rush Personal Training Blog

LISS or HIIT for Fat Loss

LISS or HIIT for Fat Loss

Which type of cardio should you be doing to Burn Fat?


I felt it necessary to tackle this confusing subject after seeing increasing numbers of social media fitness trainers and companies advertising how HIIT (high intensity interval training) can “MELT” yes, melt fat away. Okay fair enough, everyone is entitled to their opinion but let’s see if they are actually helping you or just trying to sell you products with the link at the bottom of their page advertising fat burning pills.

Don’t get me wrong, the internet can be a great place for advice but be careful as most information is the opinion of one person and not necessarily scientific based guidance which would help you reach your goals more efficiently.

Yes, I am another fitness professional giving my opinion, but my advice is constructed around scientific evidence through years of trials and studies by leading specialists.

Over the last 12 years, I have experimented with different types of training before implementing it with my clients, so the comparison below has also been based on real successes with real people.

After fighting the losing battle myself and hearing the same questions constantly, I wanted to compare the two popular styles of cardiovascular exercise and prove which one is better for “FAT” not “WEIGHT” loss.

My goal is to show you the pros and cons of each and which one will actually help you achieve the body you set out to see.

Okay, let’s begin…



HIIT is an abbreviation for High Intensity Interval Training. Over the years, there have been many variations formed but they all point to the same 2 ideas.

1. Switch between short bursts of effort and rest periods

2. Bursts of effort should be maximum effort

For example; you could go all out on a spin bike for 30 seconds, then stop for 30 seconds before repeating a set number of times. This method is explained as a 1:1 ratio, which sees you completing one period of hard work followed by the same period of rest.

There are many different types of HIIT training, and you could even design your own work/rest periods which would ultimately have the same outcome. They are even given special names now, like Tabata, which follows a 2:1 ratio. So, for example, 30 seconds on, followed by 15 seconds rest. A little more advanced but still follows the same principle.

Let’s look at why HIIT has become so popular and is championed by so many fitness professionals.



It has become a go to method for trainers and individuals a like but why? What’s so great about it?

Here’s 4 reasons why people have made this their choice for cardiovascular exercise.

1. Quicker workouts

As with everything these days, everyone seems to want things as quick as possible and that’s no different when it comes to exercise and speed of results. Why train for an hour or more, when HIIT provides a workout within 30 minutes. Who can refuse the temptation of maximum results in half the time?

Studies have shown that HIIT training outperformed longer distance training by up to 10% considering cardiovascular benefits.

So, you can train for as little as 16 minutes compared to an hour of jogging and receive better results. Who could refuse?

2. Burn more calories

Not only does HIIT training increase cardiovascular (heart) functionality but it burns lots of calories too. That’s right, studies have shown that HIIT can use 6-15% more calories compared to basic steady state cardio. The important fact to remember is that not all of the calories are used during the exercise itself but actually afterwards, through an effect known as Excess Post-exercise Oxygen Consumption (EPOC).

EPOC is the effect of your body is restoring itself to pre-exercise levels. This is due to the increased work your body has to put in to replenish itself after the such vigorous training endured during HIIT training and as with most of your bodily functions, this requires energy, so your body can continue to burn calories for hours after your session. Wow!

3. Improve performance

HIIT training isn’t a one sided method, it also gives individuals an opportunity to condition themselves for a certain sport or discipline by providing match style conditions. It can replicate the start/stop style of sport like football or rugby with the shorts bursts followed by recovery periods, which can prepare athletes more efficiently than the slower/longer periods of exercise.

It can also increase explosive speed, power and agility, which are all crucial towards improving an athlete's performance.

4. Convenient

One of the main reasons for the increased presence of HIIT in the fitness industry is the availability of home workout plans provided by clever marketing campaigns and leading fitness companies. Who can resist the chance of looking like the ripped models on social media adverts, all in the comfort of your own home. There’s no need for expensive gym memberships, personal trainers or equipment, these workouts can be completed in front of your television for only 20 minutes a day. It sounds like a no-brainer.



Unfortunately, as with anything, it’s not for everyone. So, is it for you? Let’s look at how it could have a negative affect on your fat loss goals.

By looking at the pros, its hard to think there could be any negatives but unfortunately there are a lot of people making plenty of money selling products concerning HIIT, so covering up the bad points might be in their best interests.

Fortunately for you, I’m not looking to profit from it, so lets unveil the truth.

1. Gruelling

Even though getting your dream body in half the training time as standard workouts may seem appealing, there must be a catch. And yes, there is. The 100% effort required over the working periods which can certainly take its toll on your body. This might be sustainable for a highly tuned athlete but for the average Joe’s, this is a lot of work to complete in such a short amount of time. Yes, you can condition your body to such workouts in the long-term but initially you will have to put your body through gruelling tests to reach your goals.

2. Dangerous

As mentioned, HIIT puts a massive strain on your body and not just on your muscles.

With anything new, your body will need to adjust but HIIT, its 100% maximum effort from the get-go, so your body doesn’t get a warning as such. It’s thrown straight into the deep end, which carries its own dangers.

Conditions such as rhabdomyolysis, which is a muscle and kidney condition has been strongly linked with HIIT new comers. It is a condition caused by the body being pushed to its limits and sees exercisers experience nausea, fever, and vomiting.

This can then lead to exhaustion, which encourages poor form, leading to unnecessary injuries.

Unlike Personal Training, HIIT is usually undertaken without supervision, which can carry its own problems, especially when pushing the body to its limits. There is always something to be said about learning the correct techniques initially, so you can be sure you are performing exercises correctly and in a safe manner. This can save a lot of pain further down the line.

3. Extra recovery time

Pushing your body to the extreme carries the risk of stress on your muscles, joints but more importantly your heart. So, your body will require increased recovery time compared to lower intensity sessions.

It is recommended that HIIT shouldn’t be performed for more than 40 minutes in total per week and at least 24 hours recovery is introduced before exercising again.

It might only seem like a 20-minute workout, but the 4-6 minutes of maximum effort definitely takes its toll on the body and a lot more taxing on the body than it feels. This is where the increased risk of injury creeps in.

4. Hormonal imbalances

The increase in cardiovascular and muscle strength are definite benefits of HIIT training but this can lead to unwanted stress on your body and also your mind. This is definitely not something we need more of with the ever-increasing stressful situations in our lives.

When we train at maximum intensity, the production of hormones increases. These include; growth hormone, testosterone, endorphins, epinephrine (adrenaline), norepinephrine (noradrenaline), cortisol, and aldosterone are the most obvious.

In the face of trauma to your body, the adrenal glands produce cortisol which tells your body to break down muscle to use as energy for your muscles. This is more prominent in HIIT as your muscles need more energy to move.

In normal circumstances your body can handle the release of certain hormones, but the problem arises when the body is already under added stress – like mental, emotional or work-related stress, and extra stress is added through HIIT training. This results in the adrenal glands becoming overactive, and the overproduction of cortisol, which eventually could lead to condition known as adrenal fatigue. This can cause poor sleep, low energy, weight-gain or weight-loss, and a host of other unwanted symptoms.

Now lets look at an alternative;



LISS is an abbreviation for Low-Intensity Steady State, or sometimes known as Low-Intensity Sustained State. In simple terms, it means performing aerobic activity at low intensity for a prolonged time period.

In short, aerobic activity is anything that raises your heart rate, which suits low intensity training as the idea is to keep your heart rate between 50-60% of your maximum. Maximum heart rate calculators can be used to find your ideal numbers, but an easy formula is;

220 – (age) = MHR

So, for example, I'm 35 years old, so 220 - 35 = 185. So, 50-60% of my max heart rate would be 92-111 beats per minute. This is still efficient enough to be classed as exercise, but nowhere as gruelling as a maximum effort HIIT workout.

LISS cardio workouts typically last between 30 to 60 minutes which can be seen as prolonged compared to the shorter time periods of HIIT.



How can LISS lead towards your fat loss goals.

Okay yes, compared to HIIT, LISS may sound boring but I feel it’s benefits out way the mental numbness.

1. Results are pretty much guaranteed

The speed in which you move doesn’t dictate the number of calories used but the amount your body moves can be a factor. So, by walking a certain distance in a quicker time will have little impact on the calories used.

The best part about LISS, is the fact your body will be in the so called “fat burning state”, which can often be misunderstood. Let me explain, when you exercise less intensely, your body can afford to produce more energy aerobically (i.e. using oxygen), which allows it to burn an increased percentage of fat for fuel.

This doesn't necessarily mean that more fat will be burnt in total, but LISS cardio will put your heart rate in a range that burns a greater number of calories from fat during exercise. This proves that you don't need to move quickly to burn calories or fat.

2. No real dangers

LISS involves more slow controlled motions compared to the faster impact movements of HIIT. Hence why walking is deemed one of the safest forms of exercise you can partake in.

It is obviously important to stay as injury free as possible to progress but the increased potential for injuries involved with HIIT definitely makes LISS look like a safer option.

3. No recovery times

Unlike HIIT, LISS doesn’t need as much recovery time, so you could potentially exercise daily as your muscles and joints will be less fatigued and your stress hormones won’t be triggered, leaving you free to burn that fat daily. This is perfect for anyone wants to increase their exercise but doesn’t want to be limited to the amount they can train during the week.

4. Convenient

As with HIIT, LISS doesn’t require a gym, equipment or instructor but the main point is that there is no instruction needed. It can be completed at very short notice and pretty much anywhere.

HIIT training would have you sweating, and a change of clothes would be required if you were looking to return to work on your lunch break, but this wouldn’t be the case with LISS. At 50-60% MHR, you would be far pushed to break a sweat, so you can complete a swift 30-minute walk and return directly to work knowing you’ve done your exercise for the day.

5. Sustainable

LISS will not only help you avoid injury, but it also provides a form of exercise that can be followed for life.

I don’t know about you but there are some days where training seems like the last thing I want to do and giving 100% effort isn’t something I can commit to. Working at 50-60% however is something that is a little more achievable.

Of course, there will be days when you don’t want to complete any exercise, but rest is important too!

Evidence shows that the type of exercise which will give you the best results, is the one you stick to. After all, consistency is the key to success. LISS has been proven to be more enjoyable than HIIT in the long-term.


As we know, everything has its drawbacks, so let’s look at why LISS might not be the one.

1. Plateaus

If you have trained for a certain amount of time, I am sure you have experienced a plateau at some point. This is the moment your body stops changing, mainly due to the same routine being followed time after time. There will become a point where your body adapts and stops reacting to the exercise you are completing.

To continually see progression, you need to follow principles such as “the Progressive Overload Principle” which states that you must regularly challenge your body in order for it to adapt and eventually change. So, if you want to look different to how you currently look, then you have to do something different than yesterday.

Unfortunately, with LISS, it is difficult to continually challenge your body unlike HIIT, where every session should be a challenge.

Due to LISS being limited in its variety, it is easy for your body to become accustomed to your training routines, so you will eventually stop changing. With this method, you could easily hit a plateau which will be difficult to break.

2. No afterburn

Excess Post-exercise Oxygen Consumption is the effect which occurs after HIIT exercise or strength training. This allows your body to continually burn extra calories for hours after workouts as it replenishes itself. AKA “The Afterburn Effect”.

LISS unfortunately doesn’t create this effect as the intensity relatively low, so your body is able to handle your workout efficiently. This leaves no oxygen or energy to be replenished after your cardio workout, so your body will stop burning fat for energy.

3. Slows down Metabolism

Have you ever heard the fact, “muscle burns calories”? This is because every pound of muscle you have, has a great metabolic effect. Your muscles can incredibly use up to 50 calories for each pound of muscle per day.

That may not be a lot in a day but even an extra 5 pounds of muscle added could burn up to 1750 calories per week without completing any extra exercise.

But this also works the other way. If you reduce your muscle by 5 pounds, your metabolism will decrease by the same number of calories per week and 1750 is a substantial number when it comes to fat loss.

LISS has its place when it comes to cardiovascular health but unfortunately not when it comes to being muscle. In fact, it could actually have a detrimental effect on your muscles and see them deteriorate over time.

You may see some initial weight loss but once this becomes muscle loss, the progress will be hard to come by and weight loss could stop altogether until a new challenge is introduced.

Without building or maintain muscle mass, metabolism naturally slows with age which becomes increasingly problematic as you age as your metabolism is already in a natural decline. Too much LISS can actually speed up the process of a slower metabolism.

4. No improvement in athletic performance

LISS definitely isn’t for anyone looking to improve their athletic performance. I can help your body actively recover after intense workouts, but it will not help towards improving speed, agility or strength. More intense, explosive training is needed to increase athletic output.


HIIT vs. LISS Conclusion

After looking at pros and cons for both types of exercise, we can now summarise which one suits your specific goal.


HIIT Exercise

Quicker workouts

Burn more calories after training

Increased athletic performance

Can be performed anywhere

Not overly enjoyable

High chance of injury

Long recovery times

Negative effect on hormones


LISS Cardio

Quick weight loss results

Very safe​​​​​

No recovery times

Can be performed anywhere

Enjoyable for most

Can reach plateaus

No calorie afterburn

Slows down metabolism

No athletic performance improvements


HIIT and LISS are almost complete opposites. Some HIIT’s benefits are LISS’s limitations and vice versa. The main thing to take away, is “DO WHAT WORKS FOR YOU AND SUITS YOUR GOAL”. Don’t follow an exercise plan because it works for someone else, as they are not you and may not have your overall vision of what happy is.