You walk into the gym, ready to work hard and blow-torch some fat.
You step up to the row of shining cardio machines—treadmills, bikes, ellipticals, rowers—you choose your favorite and tighten your shoes. The fancy new touchscreen display looks back at you: What do you want to do? A 10k? Hill climbs? Intervals?
Maybe you’ve heard that shorter, high-intensity cardio is better, so you reach for the “intervals” button. But you’ve also heard that the more cardio you do, the more calories you burn… so, 6 miles? 10? What’s the right choice?!
You’re about to witness an epic battle between two of the titans in exercise: long slow cardio and high-intensity interval training. Who will win?
Let’s find out.
Energy Balance: The First Battleground
To lose fat, you have to be in an energy deficit. That means burning more calories than you eat or drink. There are three ways to do this: eat less than you need to maintain your weight, exercise to expend more calories than you normally do, or both.
If you’re really on a fat loss journey, you should always take care of your nutrition first—that’s where you can make the biggest difference and take the most control over your body’s energy balance. But that’s not really the point of this article. If you want to know more about that, check out these articles:
- How Important is Exercise for Burning Calories?
- Everything You Need to Know about Dieting
- Why You Should Actually Prioritize Quantity Over Quality When Dieting
We’re going to cover the exercise side of the equation. And, when it comes to exercise, most people think of the calories you burn while you work out. That’s a big part of it, but you can also burn extra calories after you leave the gym. Your body still needs to recover from exercise, and that takes extra energy. In fancier terms, this is called Excess Post-Exercise Oxygen Consumption, or EPOC [9]. The debate really starts here, because different types of cardio burn different amounts of energy and affect EPOC is different ways.
So, what dictates how many calories you’ll burn after you stop exercising? Intensity, or “effort level.” The general rule here is: with easier exercise (lower intensity), fewer calories get burned afterward [1]; with harder exercise (high intensity), more calories get burned afterward [2].
Normal, slow, long-distance or long-duration cardio is called Low-Intensity Steady State, or LISS. When you get on the elliptical and slog it out for 45 minutes or spend an hour on the treadmill, this is what you’re doing. But, in the past 10-15 years, a new contender has taken the weight loss world by storm: High-Intensity Interval Training. The cool kids call it “HIIT,” so that’s what we’ll call it, too.
As the name implies, HIIT is very intense. Think of running sprints with short-to-moderate rest periods, or doing a 20-minute circuit of intervals on a bike… the lung-burning, soul-sucking stuff that leaves you out of breath: that’s HIIT. Because it’s so hard, HIIT burns a lot more calories during EPOC than light cardio [2]. A hard HIIT workout can leave your body’s metabolic processes out of whack for a long time, making it hard to get back to baseline. Thus: more calories get burned later [2]. HIIT has been shown to elevate EPOC levels for 20+ hours after exercise, far more than after a LISS workout [9].
Round 1: Which Burns More Fat?
This isn’t just a debate among bloggers: Science has been hashing out the pros and cons of HIIT vs LISS for years now.
For instance, one study looked at the effects of both kinds of cardio on body weight [2]. Two groups did 12 weeks of cardio training, with one group performing only long-duration cardio workouts while the other did HIIT. Both groups lost an average of about 7 lbs, with equal drops in body fat. This kind of result, where both kinds of cardio seem to be equally effective, isn’t weird—it’s actually the norm. Both regular cardio and HIIT are great options for losing weight, improving body composition, and increasing fitness [3,6].
“But they’re so different! How could they have the same effect?” Well, it makes sense. While proponents of HIIT will stress the glory of EPOC and how it burns more calories later, it still burns fewer calories during the workout than LISS. One burns more calories sooner—the other burns more later… and it evens out.
Round 2: Time Flies
“Alright, if they have the same basic effect, why are we talking about this?”
Time efficiency.
Even though the results of each type of exercise are similar, HIIT workouts take less than half the time of long cardio workouts, meaning you’ll get out of the gym in less than half the time [6]. Besides saving time in the gym, the speed-efficiency of HIIT means you don’t have to add as much cardio to get the same effect for fat loss! For busy people looking to decimate body fat, this could make HIIT workouts a no-brainer.
So, why would you ever do 60 minutes of jogging when you could sprint it out for 20 minutes and be done?
One reason would be the “enjoyment factor” of cardio. Because of its lower intensity, LISS is often thought to be more fun [7]. By contrast, HIIT is hard. Your heart will be pounding, your skin dripping, and your lungs burning. To some people, that sounds like something they wouldn’t touch with a 10-foot pole.
But it doesn’t have to be that way. In fact, one study showed that physically challenging (but not overly strenuous) HIIT was actually more enjoyable than long slow cardio workouts, especially once you get used to it [7]. It comes down to preference: What’s a hellacious out-of-body experience to some might sound “fun” to others. People are weird.
And the Winner Is…
High-intensity interval training is a potent weapon to have in your fat loss arsenal, especially if you get frustrated or bored by endless hours on your favorite cardio machine. It’s faster, costs you nothing, and you’ll burn more calories hanging out on your sofa afterward. That’s pretty appealing.
Ultimately, they both work, and it can come down to a matter of personal preference. But, if you ask me, the winner is pretty clear: High-Intensity Interval Training takes home the gold.
Further Reading:
References
1. Boutcher, S. H. High-Intensity Intermittent Exercise and Fat Loss. Journal of Obesity, 2011, 1-10.
2. Zhang, H., Tong, T. K., Qiu, et al. Comparable Effects of High-Intensity Interval Training and Prolonged Continuous Exercise Training on Abdominal Visceral Fat Reduction in Obese Young Women. Journal of Diabetes Research, 2017, 1-9.
3. Trapp, E. G., Chisholm, D. J., Freund, J, et al. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International Journal of Obesity. 2008; 32(4), 684-691.
4. Kong, Z., Sun, S., Liu, M, et al. Short-Term High-Intensity Interval Training on Body Composition and Blood Glucose in Overweight and Obese Young Women. Journal of Diabetes Research. 2016, 1-9.
5. Inelmen, E. M., Toffanello, E. D., Enzi, G, et al. Predictors of drop-out in overweight and obese outpatients. International Journal of Obesity. 2004 29(1), 122-128.
6. Farland, C. V., Schuette, J., Foster, C, et al. The Effects of High Intensity Interval Training versus Steady State Training on Aerobic and Anaerobic Capacity. Medicine & Science in Sports & Exercise. 2015, 47, 133.
7. Heisz, J. J., Tejada, M. G., Paolucci, E. M, et al. Enjoyment for High-Intensity Interval Exercise Increases during the First Six Weeks of Training: Implications for Promoting Exercise Adherence in Sedentary Adults. Plos One. 2016, 11(12).
8. Ohkawara, K., Tanaka, S., Miyachi, M, et al. A dose-response relation between aerobic exercise and visceral fat reduction: Systematic review of clinical trials. International Journal of Obesity. 2008, 32(2), 395-395.
9. Greer, B. K., Sirithienthad, P., Moffatt, R. J, et al. EPOC Comparison Between Isocaloric Bouts of Steady-State Aerobic, Intermittent Aerobic, and Resistance Training. Research Quarterly for Exercise and Sport. 2015, 86(2), 190-195.