When you’re in the middle of a workout you can feel your body working hard: you sweat, you shake, you breathe heavier. If someone asks if you’re burning calories in the middle of an intense gym session, you’d say yes, of course! But what about after your cool down? Do you think you’re burning calories then? According to the principles of excess post-exercise oxygen consumption, or EPOC, you probably are.
What Is EPOC?
EPOC is your body’s tendency to burn extra calories following certain types of exercise, above and beyond what it burns in the workout itself. In some circles, it’s been held up as the Holy Grail of exercise: it can be an efficient mechanism for chiseling fat from your frame, even after you leave the gym.
Sometimes you might hear EPOC called “afterburn effect.” This references the calories that are burned after a workout when your body is repairing itself and getting back to its normal resting state.
Why Does EPOC Happen?
Think about it like this: when you turn your oven off after baking a sheet of chocolate-chip cookies, the oven stays hot for some time afterwards. The hotter it was when you turned it off, the longer it stays hot.
The same principle applies to exercise: after you workout, your body remains “hot” for awhile, and takes some time for it to return to “room temperature”— meaning your normal resting state, or resting “metabolic” rate.
What’s happening in this post-workout window? Like a NASCAR pit crew, your body is scrambling around like mad: it’s dialing your respiration and heart rate back to normal, clearing waste from your muscles and refilling them with fuel, re-oxygenating your blood, and repairing damaged muscle and connective tissue. All that repair-and-recoup activity requires your body to utilize more calories and use more oxygen than it normally does. And that’s the EPOC definition in it’s most basic sense: it’s the additional energy you burn as your body restores and repairs itself following a tough workout.
How Long Does EPOC Last?
The size and duration of EPOC is determined by both the duration and intensity of your workout. The longer and harder you workout, the greater EPOC levels you’ll see.
“Repairing mechanical damage to muscles and replenishing energy systems can take 48-72 hours, depending on your physical conditioning and the style of workout you completed,” says Openfit fitness expert Cody Braun.
What Workouts Trigger the Greatest EPOC Levels?
Since this is a measure of the oxygen you consume—and not heart rate—you can only measure it inside a lab. That makes it difficult to pinpoint exactly how much EPOC is produced from any given workout. But generally, short, intense training sessions (like HIIT) can produce more EPOC per minute of exercise than steady-state training (like distance running).
For example, if you go on a short, easy jog, EPOC may only last a few minutes. But if you do a strength-training session using short rest intervals and challenging weights, it can last for much longer. Similarly, circuit training produces substantially more EPOC than standard training; fast cycling produces more EPOC than slow cycling.
A recent study found that 20 minutes of interval training burned about as many total calories over 24 hours as a 50-minute steady-state session. And another study still found that both resistance exercise and interval training produced more EPOC than steady-state training.
It’s easy to see why EPOC is such an appealing idea: it seems to promise a perfect solution for time-strapped exercisers looking to tighten their waistlines. If you put in a quick high-intensity workout Monday morning, then the science seems to say that you can burn extra calories all the way through breakfast on Wednesday.
How Does EPOC Burn Fat, and How Much Fat Can It Burn?
Unlike most fitness myths, EPOC is in fact a real effect that contributes to caloric expenditure. However, this doesn’t perfectly translate to fat loss…although it can help. The amount of fat you burn ultimate depends on a few factors, like how much fat you have to start with and your metabolism rate. So when we’re talking about EPOC “burning” things, we’re taking about burning calories, which may in turn burn fat for some people.
With that cleared up, how many calories does EPOC burn?
Unfortunately, the most up-to-date research indicates that, regardless of whether you sprint or jog, lift or cycle, the vast majority of energy you burn from exercise occurs during the workout itself—not after. EPOC can account for an additional six to 15 percent energy burn after your workout—but rarely more than that.
That means that the EPOC following an extremely tough lifting and interval training workout during which you burn 400 calories, might only be 60 calories, or roughly the calories in a couple of unflavored rice cakes.
But that’s not bad! Churn through three to four workouts like that in a week and that adds up to quite a few rice cakes. However, it’s hardly license to binge: if you chow down on a single cupcake, that can add up to (or surpass) an additional calories might have burned from EPOC, even if you worked out at a very high intensity just about every time you exercised. But each person is different — it depends on the size of the person and how many calories they burn.
“The biggest idea to take away from EPOC is that training with a higher intensity a few times a week can add some positive muscular damage as well as additional calories burned,” Braun says. “It’s not the be-all-end-all, but for people looking to lose body fat, it will only increase their chance of success.”
This brings us back to an oft-repeated point. Exercise, in all its forms, is invaluable for cardiovascular fitness, maintaining muscle mass, strength, and all manners of athletic performance. It boosts your mood, increases confidence, and can make you look better — in your clothes and out of them. So if you’re going to put your faith in something that will undoubtedly help you lose fat, that would be a well-designed workout plan that’s performed diligently, multiple days a week. EPOC is just a nice helping hand.