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The Final Nail in the HIIT EPOC Coffin

After an exercise workout is completed, oxygen uptake (VO2) remains elevated for some time over resting levels. This phenomenon is called, straightforwardly enough, "Elevated Post-exercise Oxygen Consumption" or EPOC. The duration and total amount of EPOC varies according to the duration and intensity of the workout. The increased VO2 means a increase in calories burned after the workout as well.

A frequent rationale for promoting High Intensity Interval Training (HIIT) programs for weight loss is the assertion that HIIT workouts burn more calories for an extended time AFTER the workout. A perfunctory use of the Google will quickly uncover dozens of examples of these claims:

"HIIT increases EPOC (excess post-exercise oxygen consumption) resulting in an elevated fat loss state for up to 24 hours after you finish your workout – something you won’t get from lower intensity exercise."

And another:

"Long, slow, low-intensity cardio will produce a small EPOC effect that will at best, last only a couple of hours after the workout. Basically the 400 calories you burn during the workout will be all that you burn, because the EPOC effect afterwards is negligible. However, studies have shown that after HIIT workouts, the EPOC effect can still be found up to 38 hours after the workout - basically your body is burning fat to fuel the restorative processes for 38 hours AFTER your workout! So, even though you may have only burned 250 calories during your HIIT workout, the total calories burned after will be far greater.  Those calories, plus the 250 burned during the HIIT workout surpasses the 400 burned during the slow, steady-state workout by a LONG, LONG way."

Actually, the "studies" point out that these claims are exaggerated, to say the least, and that the effect of EPOC for all workouts is modest at best. There are plenty of good reasons to include HIIT workouts in your routine, but a supposedly elevated EPOC is not one of them. 

A 2006 study reviewed all the research that had been done up to that time on EPOC. The authors concluded that the additional calories burned from EPOC for endurance exercise was about 7% of total calories expended during the workout. Calories from EPOC for HIIT workouts were almost double, approximately 13% of total calories during the workout.

LaForgia J et. al. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci. 2006 Dec;24(12):1247-64.

Double the calories sounds pretty good, however, when comparing the effects of something like EPOC, one must look at the TOTAL calories burned, not the percentage increase and not the "duration" of the "afterburn". Looking at the actual numbers tells a different story.

80 kg individual does a 60 min endurance workout and burns 640 calories. Add 45 calories for the 7% EPOC for a total of 685.

Same person does a 20 min HIIT workout and burns about 300 calories. Even with the extra EPOC of 13%, that's only an extra 40 calories, for a total of 340.

There is no "afterburn" that is going to make up those extra 300 calories.

(For a more in-depth discussion of the LaForgia study, see Lyle McDonald's excellent review: 

http://www.bodyrecomposition.com/research-review/research-review-effects-of-exercise-intensity-and-duration-on-the-excess-post-exercise-oxygen-consumption.html)

More evidence was presented in a recent article on the website of the National Strength and Conditioning Association. Several studies were reviewed (including the LaForgia study already discussed) and showed that, even when EPOC remains elevated for 9 hours following a HIIT workout, total calories burned from EPOC only ranged from 18 to 80 calories TOTAL. The only exception was a recent study from Appalachian State University that reported a total EPOC of 190 calories over 14 hours).

As if that weren't enough, a review article published by Melanson et al in 2009 showed that exercise training does not affect 24 hour total body fat oxidation, even though it increases fat metabolism in muscle.

Exerc Sport Sci Rev. 2009 April ; 37(2): 93–101. doi:10.1097/JES.0b013e31819c2f0b.

Other studies have shown either no difference in the 24-hr rate of fat use following exercise, regardless of intensity, or, even when there was a small increase in fat oxidation following high-intensity exercise, the total amount of fat burned was trivial.

The conclusion of the NSCA article was that research:

"...suggests that EPOC is not a primary contributor to the energy cost of exercise and that it does not alter substrate use enough to be of consequence in a weight loss program."

Again, the purpose of this is not to denigrate HIIT workouts. They can play an important role in many workout programs, and, when the time comes, they are essential in order to accomplish significant body recomposition. However, like so much else in the fitness world, the benefits of HIIT are sometimes overhyped and their application frequently overgeneralized. People need different types of workouts depending on their age, body fat levels, fitness level, fitness experience and overall health. When starting a weight loss program, total energy expenditure is still a primary goal of the exercise component. Endurance cardio workouts, submaximal interval workouts, and even endurance strength workouts are usually the better choices for beginners.

21 votes + -

30 comments:

NeverCatchYourBreath wrote 48 months ago:
I like your blog post.

but periods go before " not after.

For example: "... afterburn."
Not: "... afterburn".
airant wrote 48 months ago:
OMG who cares where the periods go!!!! is the info what matter.........
airant wrote 48 months ago:
OMG who cares where the periods go!!!! is the info what matter.........
almc170 wrote 48 months ago:
...And to be equally pedantic, British quotes (i.e., period after quotes) are perfectly acceptable. It is a style commonly used in technical communication (my livelihood).

But yeah, it's a great post!
april1445 wrote 48 months ago:
Excellent information: thank you.
susanonamission wrote 48 months ago:
Good stuff. I will focus on the 600 vs the 300 caloric burn and gladly accept any EPOC that comes my way. what's the best way to burn 600 in one workout?
Quantumn wrote 48 months ago:
Run for an hour.
skillingsrobertj wrote 48 months ago:
Very nice post; clear, concise and well-written.

As for how to get in a 600calorie workout...I enjoy doing 3-4 sets of 15 minutes each on an indoor rower at a 2:20min/500meter pace. Each set burns about 150-170 calories.
ss_22 wrote 48 months ago:
Nice info. Do you have to know EPOC % and duration after weights?
Emile_Jarreau wrote 44 months ago:
Hi,

As I proof a document that will become part of a certification for fitness professionals and after 27 years actually DOING this type of training, there is merit to doing HIIT when striving for reduced fat loss.

Body weight (if healthy and not over weight)calisthenics are great to do for burning excess fat.

There is tons of research always on both sides of the "right side" of the fence as to how long EPOC lasts and its effects.

Best answer "it depends" with all factors being monitored closely...it works, but must used like anything else, cyclically.

Nice article.

Emile Jarreau, aka, Mr. Fat Loss
Anonymous wrote 43 months ago:
I find that doing HIIT on my own gets boring. Plus, I never push myself as hard as I do when I’m using this killer coached HIIT album I found on iTunes: http://bit.ly/HIIT_Mix_iTunes.
Anonymous wrote 40 months ago:
The simple answer to fat loss for overweight individuals is to restrict calorific intake of carbohydrates while focusing on good quality fat and protein sources.
Starchy carbohydrates should only be used to fuel exercise (pre-workout) and high glycemic carbohydrates to replenish glycogen stores (post-workout).
To avoid hypoglycemia throughout the individuals working day (never really a concern for desk jobs) then the occasional piece of whole fresh fruit will suffice.
For help and advice specific to the individual please contact me at
djames.dietarysolutions@gmail.com
Anonymous wrote 40 months ago:
I agree, that the statements regarding EPOC beeing "the holy grail" of fat loss are exaggerated.

May i add a couple of thoughts:
a) You wrote: "A 2006 study reviewed all the research that had been done up to that time on EPOC." This is somewhat misleading as this paper is not a review, it is a study. If you want a good overview, read this REVIEW by Boutcher (2011)

http://www.ncbi.nlm.nih.gov/pubmed/21113312

b) The study you cited: LaForgia J et. al. (2006) was conducted with 16 (!) participants. If you have a sample as small as this it is very hard to generalize your findings to the general population. The sample is just too small.

I could go into detail, but to sum it up: HIIT might be more useful than you implied in your article but further studies are needed. And most importantly, findings need to be replicated because otherwise you can not compare the results as leading scientists use all kind of different subjects, experimental designs, dependent variables, measurement methods and so on.
Anonymous wrote 39 months ago:
you know nothing.
Anonymous wrote 39 months ago:
Exercise is not all to do with the 'calorie burning' model, though, so using the total burn does not put the nail in the coffin with respect to interval training. Go and run 1 mile in 30 minutes at a steady pace, and then do the same using 100m sprints done in intervals up to 1 mile, as fast as possible (in fact take 30 mins if you wish, just make the intervals 100% all-out). It's pretty obvious that the physiology is totally different; my RER is totally different after intensive intervals because I can literally feel the difference in my breathing as my body elevates its 02 demand(as it is after 20 reps squats all-out in one set, versus 5 sets of the weight with 2-3 min rest intervals). From a personal perspective I feel that interval training stimulates the burning of BODY FAT specifically and of course it could also increase muscle-sensitivity in terms of nutrient partitioning. In other words, you will get leaner with the same calorie intake!
Anonymous wrote 38 months ago:
After reading your post I had a question.

Your quote

“80 kg individual does a 60 min endurance workout and burns 640 calories. Add 45 calories for the 7% EPOC for a total of 685.

Same person does a 20 min HIIT workout and burns about 300 calories. Even with the extra EPOC of 13%, that's only an extra 40 calories, for a total of 340.”

You have compared a 60 minute to a 20 minute workout which doesn’t seem to be a fair.

What if you compared the two types of workouts by the same duration or calorie burn?

Example 1:
Using your example, the same individual does a 20 min (instead of 60 min) endurance workout and burns 213 calories (calculated linearly). Add 15 calories for the 7% EPOC for a total loss of 229.

HIIT guy also does 20 min but burns an extra 111 calories!

Example 2:
Using your example, the same individual does a 30 min (instead of 60 min) endurance workout and burns 320 calories (calculated linearly). Add 22 calories for the 7% EPOC for a total loss of 342.

HIIT guy does 10 minutes less to burn the same calories!

Am I missing something here? It seems to me like HIIT works really well.
Anonymous wrote 38 months ago:
re: anonymous and "not fair..."

An endurance session does not last 20 minutes. If you want to talk "bang for the buck," then yes, 1 minute of high intensity exercise is going to burn more than 1 minute of low intensity exercise.

But we're comparing endurance to HIIT. A person doing HIIT is not going to go for 60 minutes, and a person doing endurance training is not going to go for only 20 minutes.

If you're comparing "sessions" and not "time" and are concerned primarily with calorie burn, endurance is a slam dunk.
Anonymous wrote 35 months ago:
Your dispute is sound, however, your math is actually incomplete. Those EPOC percentage are calculated at a lump some which is saying your body takes the calories burned during the workout, figures the percentage and compounds it all at once. The EPOC effect is a decaying percentage beginning from the time you finish your workout to the time your body has fully replenished oxygen supply within your muscles. Using the examples given and compensating for percentage decreases, we have a slightly different story altogether. To make the math a little less cumbersome we'll say the percentage decays at a rate of 2% per minute and calculate for the first 3 minutes.

80 kg individual does a 60 min endurance workout and burns 640 calories. Add 45 calories for the first minute, 32 for the second and 19 for the third minute for a total of 736.

Same person does a 20 min HIIT workout and burns about 300 calories. Even with the extra EPOC of 13% to start with, burns an extra 39 calories for the first minute, 33 for the second and 27 for the third minute for a total of 399.

We could calculate it more definitely through exponential decay but the result is the same the EPOC burns more total after work out calories with HIIT because it starts at a higher percentage and in truth would burn longer.
Anonymous wrote 35 months ago:
Way too much math there bro. I just wanna say if HIIT works for you do it. I don't know how much i burned but i dropped 7 lbs in a week doing 5 minutes of HIIT (10 exercises 30 seconds each nonstop) every morning before work.
Anonymous wrote 31 months ago:
Nope you didnt.

1lb fat ~3500 calories
3500 x 7 = 24500 calories from 35 minutes of total work out?

Bit of perspective, you would have to have run approx 24 hours at a moderate/hard pace to burn of the equivalent calories
Anonymous wrote 29 months ago:
HIIT burns less calories. This is obvious and has never been disputed in scientific papers.

Fact is people who use HIIT burn more fat.
Anonymous wrote 26 months ago:
People seem to forget that HIIT's EPOC lasts for much, much longer post-exercise (24 hours) than steady state cardio (2 hours), EPOC rate is also higher. HIIT works both aerobic and anaerobic energy pathways. Usually for overall conditioning, a 1:5 work to rest ratio (0:20 on, 1:40 off) is best. If you're training for a specific event, however, do the specific training for it. Don't do HIIT to improve your 5K time. Don't do 5K runs to improve your 100m dashes.

HIIT is champion for fat loss without losing as much muscle.
Anonymous wrote 19 months ago:
Maybe, just maybe, the rate of fat burning and the total calories burned during workout dont matter that much. After all, dont we all know several folk doing the "fat burning cardio" with dispalyed calorie burns in the hundreds or over a thousand, that never seem to make progress?
Anonymous wrote 19 months ago:
"Maybe, just maybe, the rate of fat burning and the total calories burned during workout dont matter that much. After all, dont we all know several folk doing the "fat burning cardio" with dispalyed calorie burns in the hundreds or over a thousand, that never seem to make progress?"

It matters if you are one that closely follows a diet.

Diet is king. If one is not following a proper diet, then fat burning techniques are pointless.

One can exercise and burn more calories, lose weight, and still have a high fat percentage.

Skinny-fat people exist.
Anonymous wrote 7 months ago:
Ok but your math is just so obviously wrong.

The idea behind HIIT is equivalency.

By your math 736 calories burned over 1 h of long slow cardio would be equivalent to. 20 min of HIIT (689 calories) in JUST 20 minutes. Do 2 more minutes 10% more and you burn the same number of calories as a long run ( and, as the theory goes), preserve more muscle. More lean muscle mass provides more EPOC AND general calories burned over the course of a day and during exercise.

Less long term endurance injuries faster recovery
Anonymous wrote 7 months ago:
The main difference here is when doing HIIT you are building lots of lean muscle due to using your own body weight. More muscle=less fat and the higher your metabolic rate the better!
Anonymous wrote 7 months ago:
Cardio-exercise burns more fat than carbs and the opposite goes for high intensity exercise.

HIIT and similar exercises do not use fat predominantly as an energy substrate because fat is harder to metabolize than carbs. Glucose is a "quicker" energy source for intense exercise while fat is more suited for long duration low intensity efforts.

Thus, walking like 5km. in the morning and evening (which you can do every or every other day) will result in greater fat loss than a 20 minute HIIT (which will need at least one recovery or rest day). High intensity training is better suited for strength and speed purposes not fat loss.

The best thing to do is just to combine these training methods in your workout program along with a good diet plan. Additionally, do not forget to do a flexibility program like yoga, pilates and such.
Anonymous wrote 5 months ago:
Scientifically, if you spend no time bitching about which training method is better, and trying to seem smarter than the other troglodytes sitting behind a screen munching Cheetos you will burn more calories and fat no matter which method of training you do. Also, after you do it for awhile you can tell people IRL what method you use, and they will probably listen, because let's face it...you work out!
Anonymous wrote 5 months ago:
Hahaha... "cheetos." I was thinking the exact same thing as the comment above.

Personally, I'd rather do my 20 min HIIT workout for 340 vs 60 min LISS at 685. I AIN'T GOT TIME FOR THAT and it is BORING!

If your HIIT consists of some proper form kettlebell swings, snatches, get-ups and burpees, you will see some muscle hypertrophy too. You won't get that from a treadmill.
Anonymous wrote 3 weeks ago:
i did 15 mins hiit and then 45 mins weight training in my last workout...so what is my epoc?

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