It’s time we settle this debate. It’s a battle as old as time itself. Is High Intensity Interval Training (HIIT) or Moderate Intensity Continuous Training (MICT) better for fat loss? Luckily, there was a recent meta-analysis published that provides some interesting insight on what the answer might be.
In this post, we will uncover what the met-analysis showed, what it means for you if you do cardio, recommendations on which method to do based on different circumstances and situations, and I’ll finish with putting in a case for cardiovascular training that you may have not considered. For the sake of ease, we’re going to lump HIIT and SIT (Sprint-Interval Training) together because they are similar forms of activity.
So everyone is up to speed, let’s quickly define the two terms. HIIT is typically a series of quick and intense bouts of training where an exercise is repeated either for reps or a certain amount of time while going all out and pushing near 100% with each interval. After the reps are met or time is up, you rest shortly for usually no more than a minute and then you do it again. Think of Crossfit or Tabata workouts for HIIT inspiration.
MICT, on the other hand, is your typical cardio. When people say the word ‘cardio’ you probably think of treadmills, StairMasters, and ellipticals. That’s MICT for the most part. Another part to it is that you don’t adjust the intensity of the exercise. So you stay on level 6 for 20 minutes, for example, without any significant changes.
Before we move on, I want to preface the discussion with this: Cardio is not necessary for fat loss or weight loss. If you’re doing cardio only for these reasons, you’re going to hate your gym life and make yourself miserable. There are a myriad of athletes who don’t do cardio and cut weight just fine such as powerlifters. Of course, if you’re prepping for a bodybuilding show, cardio is a bit more necessary but it’s a short-term endeavor which is more acceptable. Don’t feel pressured to do cardio to lose weight. Refer to my blog post on calories in, calories out to learn how to learn more how fat loss works and how to establish a caloric deficit to really get on track with your goals.
Okay, now that that’s out of the way, here we go.
Good news is you can really pick whichever form you’d like, because the meta-analysis showed that both methods are equally effective for fat loss. An important point to note here is that the experiment was matched for energy expenditure. This means that the subjects doing HIIT burned the same amount of calories as the people doing MICT¹ during the experiment. Since each method is equally effective, then choosing which method you want to use could be based on things like the time spent on the activity, desired rigor, and personal preference.
On other important note to consider is the degree to which both methods were effective, which wasn’t a lot. Both HIIT and MICT contributed to a body fat reduction of less than 2% on their own. So yes, these methods can be used to elicit fat loss, but probably should not be used on their own. If you’re just doing cardio but not in a net calorie deficit, you won’t experience weight or fat loss. There may be some other benefits you see like improved mood, for example, but body comp. changes may not be seen. That’s why establishing a calorie deficit is nearly essential while incorporating weight training can increase the rate of loss while improving you health further and the way you look if you’re wanting to add muscle. Basically, you can’t just do cardio and not care about our diet or training and expect to shed pounds of fat. Cardio’s effect isn’t that significant!
For time constraints, HIIT is clearly the better option. You can knock out rigorous bouts of training using a seemingly endless variety of exercises in 5-10 minutes and then you’re done.
In addition, if your goal is to build some muscle, this is also a good method, as it may have some crossover effects. Think about it: you’re still likely lifting weights as part of HIIT, so you’re getting in some volume, although the benefit will be likely be minor, if any.
Another touted benefit of HIIT is potential appetite suppression. The meta-analysis pointed to some studies that showed there is a potential suppression of appetite when doing sprints or other forms of HIIT¹ when compared to MICT; although the research is inconclusive because other studies were cited that showed no change, so it’s still up in the air. For you, this is an excellent chance to experiment and see if that works for you or not!
One important note is that HIIT should be VERY hard. In the study, they define HIIT as “80-100% of peak heart rate or aerobic capacity”¹, meaning, this isn’t a bit of huffing and puffing, and then you’re done. HIIT is meant to very intense, so you should be bent over heaving and gasping for breath and possibly on the floor by the end of whatever you did.
It’s not a walk in the park. It’s more like a sprint in the park because a bear is chasing you and is right on your ass. This is a great transition to talk about the cons of HIIT, because there definitely are some!
HIIT is not for everyone. People who never trained before and overweight and obese individuals are perfectly capable of doing some form of HIIT, but it may not be the best option initially because it can come with an increased susceptibility to injury. For an obese person, the quick movements at near-maximal effort, jumping, etc. can be especially burdensome since they carry around a lot of extra weight, damaging their joints and/or bones. For a newbie, it’s a lot of extremely intense work hat they’re not used to, potentially scaring the person away from any form of exercise if you throw them in the deep end at the beginning.
Last con is that cardio is not weight training, and so precautions should be taken if you are weight training to ensure that your HIIT is not interfering with your lifting performance. Some people get very sore from HIIT, which could hinder their lifts. Plan accordingly and give yourself enough time to recover from HIIT if you also plan on lifting weights.
This is not to say no obese person or newbie should never start with HIIT. Some people enjoy the challenge and feeling the burn in their lungs from the get-go and can do it safely; others need to ease into it. Either one is fine, the safety is what’s ultimately important, so you don’t bust your ass trying to do a kettlebell swing.
We can quickly breeze over MICT because it’s bascially warranted whenever HIIT isn’t appropriate as mentioned in the previous paragraphs above.
MICT is the better option if you simply enjoy it more and don’t have time contraints. If you don’t like feeling like you’re about to die (exaggeration) from your cardio, then HIIT probably isn’t up your alley, not to say you can’t work up to getting better a tolerating it.
MICT is also better if you’re dealing with some type of injury. If you have a back injury that prevents you from bending over or causes pain with rotating your torso, MICT has plenty of ways where you can still do cardio without those problems arising.
If you’re overweight, obese, or are new to the gym/cardio, I recommend MICT because it’s a great way to ease into exercise without overloading to dangerous levels of work.
I don’t recommend MICT-or any form of cardio for that matter-if you think that it’s the only way to lose weight, by running on a treadmill for hours. As mentioned before, cardio is not necessary for fat loss. All these reasons for cardio should be supported by the fact you enjoy the training, not because you think cardio is the only way to lose weight.
In short, HIIT and MICT have both been equally shown to influence fat and weight loss (to a small degree). Cardio-however you do it-is simply another tool in your fitness tool belt. You can decide to use it or not. HIIT is good for time constraints, augmenting your lifting, and possibly for appetite suppression. MICT is effective for beginners or overweight and obese people, those concerned that HIIT may interfere with their weight-training sessions, and those who just enjoy getting in some movement without feeling like death.
Have some thoughts on cardio? Comment below and tell me what you think!
¹Keating, S. E., Johnson, N. A., Mielke, G. I., and Coombes, J. S. (2017) A systematic review and meta‐analysis of interval training versus moderate‐intensity continuous training on body adiposity. Obesity Reviews, 18: 943–964. doi: 10.1111/obr.12536.