The afterburn effect, truth or myth?

It is unlikely that you hear people in a gym talking about excess post-exercise oxygen consumption, or EPOC, because it is much better known as “the afterburn effect”. The idea behind the afterburn effect is simple: when you exercise at a high intensity for a short period of time your body will need extra energy during the recovery period to restore your body to normal working order. This means that in the hours after you finish your workout you burn more calories no matter what you are doing than if you had not triggered the afterburn effect. It seems so simple, but there are still loads of misunderstandings around this magical afterburn effect.

Myth: you burn extra calories without any extra effort

The reason that your body burns calories after a high-intensity interval training (HIIT) is because you trained at such a high intensity that many of the processes in your body are disrupted. Your body temperature will be increased, the stored energy in your muscles needs to be replenished, lactate that has built up in your muscles needs to be transported away, oxygen levels in your blood and muscles need to be restored, etc. All this will require extra calories to bring it back to a normal level.

But you did not reach this level without any extra effort in the first place. To trigger these responses you will need to perform high-intensity interval training first which requires you to train at your absolute maximum level for short intervals of time. This will be very demanding and therefore it is a myth that you burn it “without any extra effort”.

Myth: the longer your HIIT training lasts the greater the afterburn effects

It seems obvious that a long HIIT training session has bigger effects but it is not true. The idea behind HIIT training is to have intervals of 20–30 seconds where you go at your absolute maximum of your ability. If you are able to go on longer you are simply not going at your maximum. And this holding back will limit your afterburn effect. So a longer training session does not result in a greater afterburn effect; it is more likely that you lower your efforts and have a smaller afterburn effect. An average HIIT training should last about 25 minutes including a 5 minute warm-up and a 5 minute cool down.

Myth: the afterburn effect will help me lose kilos of fat

The energy source used by your body to recover from your intense workout is often fat, which is good news for when your goal is to lose some extra pounds. But you should not expect miracles from this afterburn effect. In the 24 hours after your training your body maybe burns an extra of 50 to 250 calories. Given that 1 gram of fat gives about 9 calories you can see that this, at best, results in burning only 30 grams of fat.

Truth: While the afterburn effects of HIIT are limited, HIIT is still useful to lose weight

Instead of doing HIIT to profit from the afterburn effect you should do HIIT to increase your overall fitness level giving you the ability to work out at a higher workload. This will result in more calories burned during your exercising resulting in a larger caloric deficit (the difference between what you eat and what you burn) and weight loss.