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Does High Intensity Training Help with Fat Loss?


I've been doing a little bit of research today in response to some discussion in the T-Nation fb page. A couple of things I've always assumed to be true - and have observed in myself - may not actually hold true.

I've always been a big fan of high intensity training. My observation is that it torches fat, improves body composition and raises metabolism causing you to burn more calories at rest.

Apparently this isn't true.

It's known that short burst, high intensity training doesn't burn many calories. However, it's believed by many to result in an 'after burn'. Excess Post-exercise Oxygen Consumption (EPOC) - supposedly the body has to work hard for hours or even days after intense exercise and that causes it to burn more calories.

Well, apparently (from what I'm reading - who's to say it's right), that after burn is pretty insignificant. And to make matters worse, as you get fitter the amount of calories burned after exercise reduces.

So why do so many people (including me) swear by high intensity training? What is the real reason that it seems to improve body composition and torch fat?


Wait, so, science is stating something "shouldn't work" even though a large number of people in the gym are doing it with visible, tangible results?

Yes, 'tis a conundrum. What to do, what to do.


It's not saying it doesn't work (lead to fat loss). Rather that it doesn't work for the reasons we think it does.

Understanding WHY it works can help us to better optimize our training programs to get the best return on investment.

As an example, this (high intensity training helps with fat loss) came up on the fb page and when someone said "it doesn't work for me" they were told it must be because of a crap diet. Well, if our understanding of WHY it works is flawed how can we make claims like this?

According to the research I was looking at (and we all know that research ALWAYS needs to be taken with a pinch of salt) high intensity training DOESN'T increase metabolism. The more high intensity training you do and the fitter you get the quicker your body will recover and in actual fact any 'afterburn' will be reduced. So a fat unfit person will have a higher metabolism than a lean, fit person. High intensity training (like most forms of training) will actually lower your metabolism.

You must also remember that for many years people were saying that low intensity, high volume training was working. Many people have lost fat on that. People have a tendency towards wanting to believe in the things that they invest time and money in so you can't always trust anecdotal evidence. All the people that lost fat on endless cardio (because there ARE lots of them) - was it down to the cardio or something else? Why doesn't it work for everyone? That said, I've ALWAYS felt that I do well on high intensity training. I've been making that claim for 30 years - long before it became fashionable. But the more I think about it the more I'm sure that it isn't because of an 'after burn' or increased metabolism.

My best guess right now is that it's to do with appetite regulation. We get leaner because we eat less when we train in certain ways. There is some research to support that.


We can make that claim because the most basic formula is Training + Nutrition = Results. If results aren't what we want, and the training is on point (as in, a goal-appropriate program being correctly implemented), then nutrition is the remaining variable.

I'd say this is more dependent on lean body mass rather than "fitness". A "fat unfit" guy who has 150 pounds of lean body mass and 100 pounds of bodyfat would have a lower metabolism than a guy with 225 pounds of lean body mass and 25 pounds of fat.

Again, you can't look at training irrespective of nutrition. Back in the day, when low intensity, long duration cardio was being pushed for fat loss, "eating for performance" with plenty of strategic carbs wasn't a popular concept for fat loss. If it was, you wouldn't see as many people getting as much progress because they're not complementary approaches.

If you choose to train a certain way, you can absolutely make or break your progress by choosing a nutrition plan that doesn't align with that training. For example, some lifters will undereat on Starting Strength. The program is designed to build strength and maximize recovery, but they hamstring themselves by trying to cut on a reduced-calorie diet at the same time.

I disagree. The majority of lifters I've talked to find hard, intense lifting to be an appetite stimulant. It's not unusual to hear of guys attacking buffets after a brutal training session.

EDIT: And as an anecdotal comment, I actually had a cardio kickboxing class last night for the first time in a while. I ate as usual post-workout (one meal, a while later one shake, and then sleep) and woke up this morning starving.

Was my metabolism still stoked 12 hours post-workout? Was my appetite stimulated by an intense interval cardio session it wasn't used to? Maybe, probably. But I'm not concerned with digging too deep into the why's, because in a lot of ways, why doesn't matter. I'll make a note of it, see if it happens again next class, and adjust my nutrition accordingly.


Pushing a sled works for me. I have had noticeable results in increased appetite for a day following a sled session. Without changing my diet, pushing a sled three times a week brought be down from 218 to 202 pounds.

If it works for you, why are you questioning the effectiveness of HIIT it rather than the validity of the articles you read?


Based upon my own experiences I'd dispute that 'most basic formula'. For me nutrition has zero noticeable effect. I thrive on a junk food diet and have done all my life. How I train is what makes the difference in both performance, health indicators and body composition.

But that aside - maybe I'm an exception to the rule. The fly in the ointment in that case is what if the training ISN'T as point on as you think? If the training isn't doing what you think it's doing then maybe you need to change the training rather than mess with the diet?

This highlights an example of what I'm getting at.

According to the research I've been looking at:

One pound of fat burns 2 calories per day at rest.
One pound of muscle burns 8 calories per day at rest.

So using your example (and I know lean mass isn't all muscle but we'll just assume it is all muscle for simplicity):

100 lbs of fat @ 2 cals per lb = 200
150 lbs of muscle @ 8 cals per lb = 1200

Total calories burned at rest = 1400 calories

25lbs of fat @ 2 cals per lb = 50
225lbs of muscle @ 8 calories per lb = 1800

Total calories burned at rest = 1800 calories

So the fat unfit guy did indeed have a lower metabolism.

This sounds fabulous - an extra 400 calories per day burnt doing nothing. But it's an extreme example. How many people, especially women are going to be able to build muscle anywhere near this level?

I don't know what a typical scenario for a woman is. How about someone starting out with:

105 lbs of lean mass @ 8 cals per lb = 840 calories
71 lbs of fat @ 2 cals per lb = 142 calories

Total calories burned at rest = 982

I think a woman would be doing well if she managed to gain 7lbs of muscle in a year whilst shedding fat? So lets assume a year later she has:

112 lbs of lean mass @ 8 cals per pound = 896
28 lbs of fat @ 2 cals per pound = 56

Total calories burned at rest = 948

In this example metabolism would be reduced. The lady would burn fewer calories at rest than she did when she was fat and unfit.

Now when she (and your example) were unfit there would be a more significant afterburn from high intensity training - recovery would take longer and their body would have to keep working quite hard for some time after exercise. As they get fitter they recover more quickly so the exercise results in fewer calories burned.

The lady in question might assume that fat loss has stalled because her diet is wrong - after all, she's training the right way. But a) her training isn't resulting in the same 'afterburn' as it did when she was unfit, and b) her resting metabolism is slightly lower.

Maybe her diet is just fine and she just needs to find a way to burn some more calories? Maybe a little bit of longer duration cardio would work well. (And that is what many men and women find - a mix of hitt and longer duration cardio work best).

I would hazard a guess that nutrition is a lot more important for your guy with 225lbs of lean mass and 25lbs of fat and still wanting to gain muscle mass than for my lady stalling at 112lbs of lean mass and 28lbs of fat. She's only likely to gain a few lbs of muscle a year and that won't happen for ever. Nutrition is less critical. Scope for increased metabolism is very limited and for many women metabolism will go down as they get fitter and leaner.

I honestly think that for many people a stall in high intensity training (or a failure for it to work) may simply be down to the fact that it's not burning enough calories. Introducing some longer duration cardio could well solve the problem without the need to mess with diet.

This I think is why it's important to accept that we don't know the mechanisms at play. My feeling is that a lot of people are being encouraged TOO much down the high intensity training route (with diet blamed when it's not working) when in actual fact putting a little bit of higher calorie burn training into the mix is all that's needed to get things back on track.

And your anecdotal example highlights again that we're all different and perhaps explains why the same things WON'T work for all of us. An approach to fat loss training that makes you want to eat like a pig is never going to work as well as one that burns calories without tempting you to eat all those calories back again. It'll be too hard to stick to. So yes, this supports what you say about the diet being wrong, but maybe the diet is going wrong because you're using an inappropriate training method for that individual?


Your calculations are way off based saying that any 176 lb person only burns less than 1000 kcal per day at rest. Yes, skeletal muscle might only burn 8 kcal per day, but that is not all lean body mass. Plus far more influences RMR than just bodyfat percentage.



The majority of our RMR caloric burn comes from function of the brain, heart, liver, kidneys, and lungs. Skeletal muscle only accounts for 20-25% of resting metabolic rate.

That's the point - muscle mass doesn't have as big an impact on resting metabolism as we're often led to believe. When you consider that it takes a deficit of 3,500 calories to lose a pound of fat you would need a massive increase in muscle mass to make any inroads into fat loss through higher metabolism due to greater muscle mass.

So for a typical women who (and I'm just guessing) might if she trains hard gain 5lbs of muscle in a year? Assuming she doesn't loose any fat (so an increase in overall weight of 5lbs) that's still only 8 x 5 = 40 calories a day. If she loses fat at the same time then the benefit to metabolism is negated. It's pretty insignificant. Enough to get lost in slightly altered eating patterns.

Slightly altered eating patterns would be likely to have a more significant effect - either making you fatter or thinner.


True that it takes roughly 3500 kcal to lose a pound of fat, but it takes much more than that exerted to grow a pound of muscle.


That's true.

So I start to strength train and over a two month period manage to put on one pound of muscle. In theory that will have used up 7,000 calories.

If I'd previously been eating to maintain weight and managed to put on that muscle whilst on a maintenance diet I should have lost 2lb of fat in that 2 months. However, most people struggle to gain muscle mass and loose fat at the same time. So whilst you're gaining muscle you may well be able to pig out without too much fat gain, but once you stop actually building muscle (to tackle fat loss) your calorie requirements will plummet making fat loss harder than ever. You now need to survive on 3,500 calories per month less just to maintain. If you want to loose fat at a modest 1lb a month you need to eat 7,000 calories per month less than you're used to.

So if this is the mechanism at play then the benefits (as far as fat loss is concerned) of strength training only occur whilst you're actually building muscle. And for the most part, while you're building muscle you aren't loosing fat.

So while you're actually gaining muscle (and not over eating to do so) you will see an improvement in body composition through strength training. And high intensity training with it's release of Growth Hormone could help that muscle gain.

That certainly fits with my experiences. And it would explain why it doesn't work well long term for lots of people. There is a limit as to how much muscle most women and some men can gain. Little wiry people that gain incredible strength but not much mass for example.

This is focusing on the 'does muscle mass help with fat loss?' question (another thread).

But the relevance of this is I think perhaps that high intensity training helps with muscle gain through release of growth hormone and through actually making the muscles work harder whilst PRESERVING enerrgy for muscle growth. So an important factor for success with many is that it DOESN'T use up calories that could otherwise be used for making the body bigger and heavier.

It's likely to be much more effective for a huge, muscular body buillder than it is for less muscular men and women that gain very little mass by comparison. Perhaps that's why some of us do much better when we include some steady state cardio (or some other form of high calorie burn exercise). For us the whole process of building muscle uses up considerably fewer calories so we need to either eat a lot less (which is no fun and limits scope to absorb the nutrients we need) or find ways to use more calories through training.


cmays007 posted this on the 'Does Muscle Mass Help with Fat Loss?" thread.

Does anyone know more about this?


Some good background info on Wikipedia (I hope it's ok to post the link?)

Still trying to get my head around the final paragraph on cardiovascular implications?????? :confused:


You can dispute it, but it's still true. Those are the two most basic variables available for achieving any training goal. If I want X result, I can train like Y and eat like Z. After a while, if I'm not progressing, I need to change either Y or Z. Which one I change depends on a lot of factors and case-by-case details.

To be clear, you pay zero attention to your diet? You don't try to reach certain daily protein intake, don't monitor sugar or total calories, don't keep an eye on meal timing or frequency? You eat literally whatever whenever and manipulate training frequency/volume/intensity to achieve your goals?

If the training isn't on point or isn't "working", then it should be changed. Pretty sure I said that. But again, there are more variables at play than can be usefully discussed in hypothetical situations like this.

That's what I said, because I was disagreeing with what you said, because you said "So a fat unfit person will have a higher metabolism than a lean, fit person. High intensity training (like most forms of training) will actually lower your metabolism."

It's an extreme example but it demonstrates that more muscle helps burn calories, which leads to fat loss. A woman might not be able to add 40 pounds of lean muscle, but if she adds five, we know that she'll look, feel, and perform better than if she hadn't. "Afterburn" be damned.

Sorry, but I have to call total and absolute bullshit. Gender has zero to do with the importance of nutrition during fat loss. Saying a woman should be less concerned with nutrition because she won't gain a ton of muscle is like saying she shouldn't lift heavy because she'll never bench 405.

That can be your opinion as a coach and that's fine. Lots of coaches try to achieve the same goal using lots of different methods. If you're seeing it bring consistent repeatable results in people other than yourself, more power to you and you might be onto something.

Diets are hard and sometimes we have to put on our big boy pants and tough it out. I'm not saying that fat loss need to be brutal and harsh, but "hard training makes me hungry" is not a valid excuse to avoid hard training, unless the person lacks basic willpower and self-discipline.

And for what it's worth, the morning I woke up starving, I had a normal breakfast (coffee with stevia, 4 eggs scrambled in bacon fat with a diced green pepper) at my usual time and there was no problem. Hunger-crisis averted.


During the time I went on an actual diet (as in actually measuring most of my calories and macro intake), I felt like I was starving starting around 9PMish, only 2 hours after dinner.

I went on that for 3 months. Got to the leanest I've ever been while also building (some) muscle and getting stronger.

Science works. Now if I could only find that for bulking.


Chris, this is all going off at a bit of a tangent, but to briefly address your points:

  1. No, I don't think about what I eat at all. No idea how many calories, how much fat, protein carbs and so on. I just train to reach my goals, eat when hungry and everything self-regulates itself well. That said, I eat junk. But everything from body composition to fitness, recover and health checks are very good. A few times I've tried 'eating clean' and it makes zero difference - neither better or worse.

  2. I'm not so much saying that nutrition is less important for women. More the case that I suspect it's not that important for most people. Of all the people I know and train with/around those that are lean, fit and in great shape tend not to give diet a thought.

The ones that are fat (or fatter than they want to be) - or else too thin, are the ones obsessing over what they eat. So my point really was that I can see nutrition is maybe important when you're a bodybuilder trying to maximise muscle mass whilst getting fat down to abnormally low levels - for normal athletes and non-athletes that just want to look good I don't think diet is the be-all and end all.

It's a fairly recent trend that's come about - perhaps more due to the fact that there are lots of fat people desperate to get thin and dietary advise is something that sells.

But that's all gone way off at a tangent. My question was "Does High Intensity Training Help with Fat Loss?"

It certainly seems NOT to be a good way to burn calories. Here's some research that highlights this:

A study showed that cycling for 45 minutes at 85% of max heart rate burned 519 calories during the workout and 190 after it had finished. Over 700 calories in total.

Another study found that interval training led to 225 calories being burned - in total. So that's the actual workout and the afterburn (so the equivalent of a chocolate chip cookie maybe?. This particular study was 5 x 30 second sprints with 4 minute recoveries.

So if calorie burn is your goal you'd be better of doing a hard 45 minute spin session.

Intervals are a great way to improve V02 max (in conjunction with other types of training) but they seem not to do much to burn calories.

I'm a huge fan of intervals (combined with steady state and longer duration cardio) - and I do feel that the combination of the two has a good impact on body composition. In my experience neither works well on it's own. Not sure what the role is of the high intensity training though when it comes to body composition - why does it help? It's not burning many calories.

BTW - I'm not a trainer. Just a regular person that's been training for years (and also a geek that loves all the science and research) :slightly_smiling:


Can't remember where, but Christian Thibaudeau made the point that when he wast doing crossfit training he noticed people getting better results with body composition than competetive bodybuilders WITHOUT dieting. That ties in with my experiences and my kind of training is - like crossfit - a mix of lots of different training intensities. Maybe that's the key?? Not diet at all??


You argue against HIIT, yet most of crossfit is HIIT.


I don't argue against HIIT. Little things like "I've always been a big fan of high intensity training." and "I'm a huge fan of intervals (combined with steady state and longer duration cardio)" might have given you a clue :wink:

I asked "Does High Intensity Training Help with Fat Loss?" and went on to link to research that shows it doesn't burn many calories compared to longer duration cardio.

HIIT is without doubt an awesome way to improve VO2 max - certainly in the short term. A vital part of any athletes training (in conjunction with other types of cardio). The discussion is simply about whether it plays any significant part in fat loss. The myth is that it burns huge amounts of calories because of the 'afterburn', but that seems to be untrue.


First off, you are a lucky bastard. If I eat junk, I get chubby. Im sure most people can pretty much say they are in that boat.

Second, I think the answer you are looking for isn't really gonna happen. The science is too scattered. The studies themselves might be good, but they are just small snapshots of the whole picture. Anecdotal is still the way to go, imo. Finding what works specifically for you is even better, although I understand you may be a trainer/coach too.

Not saying ignore the research by any means, just saying that science has a LONG way to go if they wanna tell me definitively that 45 minutes of cardio is better than 45 minutes of HIIT. It may very well burn more calories on the spot and a period after, but theres plenty of other factors there. For instance: when I do LISS, I feel drained and wanna sit on the couch the rest of the day. When I do HIIT, I feel like starting a mosh pit. Im hungry after doing either.

Good thing to discuss, just don't ignore what the hours of effort are teaching you, to sum it all up.


Is this whole thread a joke? Talk about paralysis by analysis, lol