The Afterburn Effect is nowhere near as effective as some “experts” claim. Here’s the science.

Is The Afterburn Effect Real Or Fake?

Written by Russ Howe PTI, and most recently updated 1 day ago.

5 min read

High intensity interval training is one of the most effective ways to burn fat because it invokes a process known as EPOC.

Many know this as The Afterburn Effect.

However, there seems to be a lot of confusion out there regarding what EPOC actually is, with some so-called “experts” claiming that as little as 20-minutes of exercise can have you burning calories for as long as 24 or even 48 hours after your workout finishes!

In this article I’m going to show you what you can really expect from HIIT and The Afterburn Effect.

Table of Contents

What is the afterburn effect?

The technical name for this process is EPOC (excess post-exercise oxygen consumption).

I’m sure you’ll agree The Afterburn Effect is much catchier.

It’s a process which is also triggered by weight training, but it’s more well-known for its association with high intensity interval training.

A traditional cardio workout (e.g. riding a stationary bike at a moderate intensity for 45 minutes) will create a significant calorie burn, and this will end the moment you stop training. Meanwhile, a HIIT workout will generally burn fewer calories in the session itself (because workouts are shorter due to the higher intensity), but it’ll enable you to continue burning calories at an accelerated rate for a prolonged period of time after your session is over.

That’s The Afterburn Effect in a nutshell.

how many calories does the afterburn effect burn

This is where the water gets murky.

If you ask ten personal trainers or fitness coaches how many calories you will burn in their workouts, I guarantee they’ll throw some fucking stupid numbers at you.

For example, there’s a gym up the road from me right now which claims:

That’s absurd.

The highest post-workout calorie burn ever recorded in academic studies is 15%, so a 500 calorie burn during a workout would return (at most) an additional 75 calories. A 2006 meta-analysis published in the Journal of Sports Science, which looked at the whole body of research surrounding EPOC at the time, concluded that you can generally expect to burn between 6%-to-15% of what you burned during your HIIT workout. (1)

The same meta-analysis also suggested that most people aren’t training at the necessary intensity to unlock the full benefits of EPOC, stating that it’s a tool which is most likely only fully utilized by athletes:

how many hours is the afterburn effect

This is another area of confusion for many, because a lot of trainers literally just make shit up.

The picture above claims that you’ll be burning fat for 30-hours after your HIIT workout ends. Furthermore, it also suggests you’ll be incinerating 600-calories per hour for the initial few hours of the post-workout calorie burn.

If this was true, you’d be dead in a week!

Trainers make these things up to sell their programs, but the problem it creates is that another trainer inevitably raises the stakes even higher by claiming that their special workout can give you even more.

(These graphics are REAL by the way!)

how long is the afterburn effect

Unfortunately, research does not support claims that you can smash out a 30-minute HIIT workout and then put your body into fat burning mode for 24, or 30, or 48 hours.

It’s more like 14-hours, and that’s the top end of the scale, as shown in a 2011 study published in Medicine & Science in Sports & Exercise. (2)

So the graphics above should look like this:

how long does the afterburn effect last

Many people dismiss the benefit of regular cardio because they believe that it cannot compete with the sheer calorie burn of a good HIIT workout.

However, science shows us this is not the case.

A 2017 meta-analysis published in Obesity Reviews confirmed that there’s virtually no difference between the overall calorie burn created by traditional cardiovascular training and high intensity interval training, so there’s really no harm in choosing the style of cardio you enjoy the most, or including both in your fitness routine. (3)

does the afterburn effect really work

HIIT does offer a few unique benefits alongside the calorie burning aspect which make it super useful, such as the shorter total workout time, improvements to explosivity, a greater muscle sparing effect, and encouraging the body to create more type 2b muscle fibers, but that doesn’t mean regular cardio is totally useless. Regular cardio will give you pretty much the same calorie burn overall, and in most cases without any high impact, which is very useful for many trainees (particularly those who are just starting out, or returning from an injury, or those who simply don’t enjoy HIIT).

So don’t fall for the bullshit surrounding The Afterburn Effect. It’s a handy fat burning mechanism which will help you get in shape, but it’s isn’t the holy grail of fat loss which is was first built up to be.


  1. LaForgia, J., et al. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci (2006).
  2. Knab, A. M., et al. A 45-minute vigorous exercise bout increases metabolic rate for 14 hours. Med Sci Sports Exerc (2011).
  3. Keating, S. E., et al. A systematic review and meta-analysis of interval training versus moderate-intensity continuous training on body adiposity. Obes Rev (2017).

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I’m Russ. I’ve been a personal trainer since 2002, and I own

My job is to simplify fitness for my readers.

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