May 14, 2023

Busting Myths and Misconceptions About The Afterburn Effect

I helped spread this week’s myth and misconception back in the day when I sold exercise for a living.

At the time, I talked face-to-face with people, convincing them they needed to pay me to be their trainer rather than putter around the gym alone.

Part of my pitch was the “afterburn effect” of my more intense workouts.

HIIT (High-Intensity Interval Training) trainers commonly use this term to describe a phenomenon called EPOC, or Excess Post-Exercise Oxygen Consumption, where oxygen consumption stays elevated after a workout while your body restores normal function, repairs muscle, and replenishes energy stores.

The cool thing about this process is that it also burns extra calories even after you’ve finished exercising, which tends to be an attractive incentive for many people in the gym.

So yes, HIIT training does deliver a bonus calorie burn as your body recovers from an intense workout.

The Spin

High-intensity interval training does appear to produce a higher EPOC effect than steady-state cardio, and the greater the intensity and challenge of the workout, the greater the EPOC response tends to be.

But while the research on the topic is fairly variable, it’s also fair to say that when you break down the numbers, my HIIT friends and I may have oversold the image of a raging metabolic furnace that keeps roaring long after the workout ends.

A systematic review of 22 studies on EPOC and HIIT found that the difference in energy expenditure averaged about 35 extra calories compared to moderate-intensity continuous exercise.

In other words, HIIT probably does not produce meaningfully greater fat loss than moderate-intensity exercise when total energy expenditure and nutrition are matched.

That aligns with multiple studies showing that HIIT and moderate-intensity training lead to similar reductions in body fat under those conditions (ref, ref).

The Skinny on HIIT

None of this should discourage anyone from doing HIIT training.

There are plenty of physical and mental benefits to pushing the intensity, including the convenience of getting more done in less time. After all, the most common excuse for skipping exercise is a lack of time.

But if weight management is the main goal of an exercise program, the most important factor is overall calorie balance over time.

The juice squeezed from EPOC is about on par with advice like taking the farthest parking spot for weight loss.

It’s not nothing. But its overall impact is small and can easily be erased over the course of a week by an extra slice of pizza or by skipping a workout altogether.

The point is to keep the focus on what is consistently attainable over the long term, not on weight-loss hacks that amount to a marginal extra calorie burn.

Originally published as Movement #189