HIIT or LISS? Which is better for fat loss?

Okay, do you want to incorporate some form of cardio into your fitness routine to increase weight loss? Something I have always bounced between is HIIT (high-intensity, interval training) and LISS (low-intensity, steady-state cardio). One reason is personal preference - sometimes I prefer HIIT and sometimes I prefer LISS, and the other is that I never properly researched either and understood the advantages and disadvantages of both. Knowing these, I am able to incorporate the most appropriate into my routine for my personal goals.

What is HIIT?
High-intensity interval training involves completing quick bursts of high-intensity exercises and incorporating rest periods in between. There are many different forms of HIIT, one of my favourites being 'Tabata', which are normally completed in around 25 minutes or less (Tabata being rounds of 4 minutes). I have a post with my at-home, no equipment workout as an example here.

HIIT has many benefits. The first being one that I've heard many people talk about: the 'after burn'. This in technical terms is known as post-exercise energy expenditure and post-exercise oxygen consumption. This is where your body continues to burn calories after you have finished your HIIT sessions, due to the nature of the training and the affect it has on your body. The amount of calories burned obviously differs to each individual, but it wasn't as much as I thought.

Those who complete regular HIIT sessions are also 'generally leaner than the ones who utilize other modes of training' according to Health Guidance. Now of course, if you complete two or three HIIT sessions you're not going to necessarily be the leanest in the room. It takes commitment, motivation and consistency combined with correct nutrition. After being a bit of a 'cardio bunny' for around a year (about a year ago) I completed many HIIT sessions per week and it was hard work. However, they were completed quickly and I could easily incorporate it into my everyday life because it didn't take up too much time.

The total caloric expenditure in a HIIT session is also significantly greater per minute than those burned in lower-intensity exercises, as well as increased lipolysis (fat breakdown) according to an article here. This means that the effects on fat loss would be significantly greater overall.

One reason why I don't incorporate HIIT into my routine more is because of the amount of weight-training I do per week. I generally 'lift' 5 times per week at the gym and use a lot of my energy doing so. When it comes to the end of my workout where I want to include a form of cardio, I simply don't have the energy to complete anything that's high-intensity. This is why I chose to include one HIIT session per week when I don't lift weights, which is often done with just my bodyweight at home.

What is LISS?
Low intensity, steady-state cardio is obviously the opposite of HIIT and requires a lower effort for a longer period of time. I choose to do my LISS as an incline walk on a treadmill for around 30-40 minutes. There are many benefits of doing LISS as apposed to HIIT, especially if you are prone to injuries or want to build up your fitness level from virtually nothing. However, neither of these apply to myself and I personally complete more LISS session per week than I do HIIT. Here's why.

As mentioned above, I find it very hard to complete a HIIT session after a sweaty, tough weight-training session and a full day of work. At the end of my 'lifting' session I often feel pretty tired and don't have the energy to do anything else high-intensity, so I opt for LISS instead.

According to Research Gate, the longer the duration of an activity, the greater the amount of relative percentage of calories used that come from fat storage. This means that more calories are burned during a LISS sessions which come from your fat storage due to you completing the exercise for a longer period of time. How accurate this is, I'm unsure. However I have seen great fat loss results when incorporating 30 mins LISS into my routine around 3 times per week when wanting to lose weight, and it means I'm not burning myself to the ground as it requires much less effort.

So... which is better for fat loss?
In conclusion:

1. HIIT does burn more calories per minute but cannot be done for same amount of time as LISS. I find that a 15 minute HIIT session will burn roughly the same amount of calories as a 30-40 minute LISS session, and some research shows more of these calories will come from fat storage.

2. If you also complete weight-training or classes at the gym that leave you with low-energy but you still want to include cardio, you will find LISS more achieveable and just as effective. This does mean you will be at the gym for longer (although it is easier).

3. HIIT may be associated with an increased potential for overtraining, especially when combined with regimented resistance training so don't wear yourself out! Find a happy medium. When trying to lose weight, I include around 3, 30 minute LISS sessions post training, and ideally 1 HIIT session per week when I'm not weight-training.

Melanie Clare