Whether you’re familiar with these forms of cardio or not, the question on whether HIIT or LISS are better than one another at burning fat and losing weight will continue to rile the fitness community for millennia.
There are countless studies analysing the health effects of interval and steady-state cardiorespiratory training but the internet is rife with misinformation, and it can be difficult to tell what’s evidence-based without reading the original research yourself.
Today I aim to break down in layman terms a meta-analysis of interval training versus moderate-intensity continuous training on body adiposity.
Lets start by describing what HIIT and LISS actually are.
Cardiovascular exercise (cardio) is any exercise that increases your heart rate, generating increased blood flow throughout the body to sustain movement. HIIT and LISS are two forms of this exercise.
High-Intensity Interval Training (HIIT) describes any workout that alternates between intense bursts of activity followed by a period of less-intense activity or even complete rest period.
An example of this would be a 30 second sprint followed by a 30 second rest period or less intense movement such as walking. You would repeat this cycle 10-15 times reaching 80% to 95% of your estimated maximal heart rate, then allow your heart rate to drop back down to around 40% to 50% during the rest period.
Low-intensity steady state cardio (LISS) are long-duration cardiovascular sessions at a target heart rate of 45-60% of your estimated maximal heart rate.
An example this would be 30-45 minutes walking pace with a slight incline on a treadmill. You’ll work up a sweat but still be able to hold a conversation.
Now lets take a look at this meta-analysis!
THE STUDY OF STUDIES
The purpose of the study was to collate data from multiple studies that have directly compared interval training to steady-state cardio training and use a meta-analysis (a statistical analysis that combines the results of multiple scientific studies) to determine whether one method resulted in greater fat loss than the other.
To coincide with the study, I will be referring to LISS as MICT (moderate-intensity continuous training) as they are the same thing.
If you take another look at the image above of the women running, from left to right, you have one representing moderate-intensity continuous training (MICT) followed by HIIT and then SIT (sprint interval training). SIT is also high intense training but at greater than 100% of ones VO2max with bursts of activity lasting eight to 30 seconds; all out balls to the wall sprinting!
The meta-analysis found 28 studies comparing the effect of HIIT or SIT against that of MICT on changes in body fat percentage and total body fat mass. Most studies were conducted in healthy young or overweight and obese adults and used cycling and running as their mode of exercise over an average of 12 weeks.
WHAT WAS DISCOVERED
There were no significant differences between HIIT or SIT and MICT for changes in body fat percentage. HIIT and SIT result in similar reductions in body fat percentage and total body fat mass as MICT, especially when matched for energy expenditure (the amount of energy or calories that a person needs to carry out a physical function such as breathing, circulating blood, digesting food, or physical movement).
However, MICT might be more effective for reducing total fat mass than HIIT or SIT, if your workout burns more calories than if you did a HIIT or SIT workout.
THE TAKE HOME MESSAGE
These results show that the type of cardio performed for fat loss (intervals vs. steady-state) probably doesn’t matter as much as the number of calories burned in the exercise session.
The most important thing, whatever ones goal is, is to follow a consistent, structured diet combined with exercise. For one thing, this has been shown to be more effective than either alone for promoting weight loss
Do the cardio you are most willing to stick to for the long-term. I wouldn’t recommend HIIT every day as you will tax your CNS (central nervous system).
Instead, do a combination of both. 1-2 days of HIIT followed by 3-4 of LISS. See what works best for you and you will see results.
- Kamal Patel. 2018. Be the tortoise or the hare: it doesn’t matter for fat loss. [ONLINE] Available at: https://examine.com/nutrition/be-the-tortoise-or-the-hare-it-doesnt-matter-for-fat-loss/. [Accessed 17 October 2017].
- Paul Jowsey. 2015. HIIT or LISS Workouts For Fat Loss?. [ONLINE] Available at: http://www.myprotein.com/thezone/training/hiit-liss-workouts-for-fat-loss/. [Accessed 1 January 2015].