Adjusting Cardio Intensity to Match Your Diet

April 6, 2009

It is almost impossible for me to recommend an exact cardio routine unless I know the diet someone is following. If someone is dieting hard and is already “carb depleted”, I am going to recommend a different cardio routine than someone who spent their past 4 days eating pizza and pasta. This is one of those cases, where a one-size-fits-all approach does not work.
man and woman doing interval training
[A picture of a man and woman doing intervals outdoors. This type of brief workout is perfect for someone who is following a clean low calorie diet.]

What is The Perfect Condition for the Body to Drop Body Fat?

There is a certain state that lends itself well to dropping body fat. That state is slightly “carb depleted”. When the body is storing a limited amount of carbs in the muscles, it tends to access stored body fat for energy. If someone is “carbed up” all the time, they are very unlikely to get lean.

Some Common Indicators That The Body Is “Carbed Up”

If you experience a 2 pound weight gain overnight, it is a good indicator that your body is carbed up. If you get really “pumped” when you lift, you are probably carrying more carbs in your system than is optimal for fat loss. If you look slightly puffier than normal, or your muscles look bigger than normal…you are probably too carbed up to get the best fat burning effect from your workouts.

The Irony About Having A Lot of Carbs in Your System

Excessive carbs in your system can give a big “pump” to the muscles during a workout. What happens when the muscles are pumped is that it can temporarily minimize the appearance of body fat. A lot of guys love going to the gym because for that 1-2 hour period of time, they can look much better than normal. The irony is that although they look better than normal while lifting, they are less likely to burn fat during their workout…so this condition will make them look worse when they are away from the gym (when it really matters).

How to Do Cardio to Quickly Reduce the Carbs in Your System

I typically tell people to avoid Marathon Cardio: which is an intense version of cardio for prolonged periods of time. Think along the lines of jogging hard for 45-60 minutes. That being said, this is a good way to burn carbs and get back to the best condition to burn body fat. So instead of waiting for 2-3 days of clean eating to get back to a slightly carb depleted state, you can get there within 12-24 hours.

When to Incorporate Marathon Cardio

This type of cardio should be used on a limited basis to get the body back to where it needs to be. Let’s say you ate pizza on Saturday and went to a BBQ on Sunday, then if you felt a bit “carbed up” you would do a longer more drawn out cardio session on Monday to get your body back to fat burning mode. From that point on you would stick to HIIT or bodyweight circuits followed by a short duration of low-to-moderate intensity steady state cardio. You would also clean up your diet for the remainder of the week.

Longer or Shorter Sessions Depending Upon Your Condition

The main thing to remember is that if you are dieting hard, you need to be careful that the cardio sessions are brief and focused (this diet and workout combo is the fastest way to lose weight). If your diet is loose you will want to incorporate longer cardio sessions to get your body to the right condition. At this point, you will want to stick with mainly HIIT and tighten up the diet.

Note:
Just use this type of cardio to avoid the state of being too carbed up. The real fat loss results will happen when you combine intense HIIT and Intervals in a slightly carb-depleted state.

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{ 42 comments… read them below or add one }

Adam Steer - Better Is Better April 6, 2009 at 4:01 pm

Cool concept Rusty.

I also like to do Metcon type workout near the end of an Eat Stop Eat style intermittent fast for similar reasons.

Cheers,
Adam

rugby April 6, 2009 at 6:45 pm

yo what if you pysically can’t do really fast paced cardio at the moment due to things like runners nee, because i need to limit my knees movment so that decreases the amout of cardio things i can do and ususally just end up on a recumbant bike or stepper for 30-45 min anywas hat gets old fast, i need some ideas.

BurritoKid April 6, 2009 at 8:02 pm

Really cool post Rust. I love it when you give lots of practical advice, and specific things we can do to live the FBB style.

do you know the effects of fasting and it decarbing the system? have you experimented with how far along you are into the fast and working out? When you are working out during fast you still do HITT?

I’d imagine waiting around 15-20 hours would be best, but I dont want to pass out.

britkan April 6, 2009 at 8:24 pm

Rusty, first your site is awsome. im trying to loose a few pounds, i fllowed bodybuilding workpout for 2 years so plenty of muscle, but i need to loose some fat.
im a very broke student, what would be the best form of cardio for me that wont involve money. thanks

Scott April 6, 2009 at 8:42 pm

What I do is I cheat on the weekend and the following Monday I go into the gym totally fasted then do a total body workout, working every muscle then cardio for 10 min. Wait an hour eat protein and fat only for the next week and cheat on Saturday. Works perfect I can have the foods I want and burn fat all week.

Jeremiah Bell (Digital Trainer) April 6, 2009 at 9:14 pm

I get my clients to do a base 1 mile run prior to every workout and then build up from there depending on their goals. I broke down the process to get a reader up to a 1 mile run here:

http://www.digitaltrainer.ca/blog/200…run-hard/

I believe that everyone should be able to do a cardio exercise for at least 20 minutes and building up to that point is important. But I do like the idea to have your cardio workouts revolve around your carb intake.

I’m hoping this means that in order to train for my marathon I better start eating BBQ for lunch and pizza for supper!

Cheers,

Jeremiah

Yash April 6, 2009 at 11:17 pm

Hey Rusty,
Good post. A question though: obviously there’s probably never a time when there’s absolutely zero glycogen in your muscles, but how can you know if it’s low enough the you’re in that fat burning window? I go by the “pump”, which I haven’t really felt in ages. But I used to do sets of 5, and now lowered to 3, so even if I was carbed up, would I know it [meaning are the reps too low to get a pump even if I’m carbed up]? I have been eating clean and healthy so I’m not too worried. Also, is there a way to store enough glycogen to have enough energy for intense activity or resistance training but still low enough to be in that fat loss zone during HIIT? I was doing fine these last few weeks with lifting without much carbs, but now I’m concerned about only being at half speed during rugby practice. Sorry to bombard you with all the questions. I usually like looking things up myself, but I like your style of HIIT so I figured I’d go straight to the source.
Thanks,
Yash

Andrew April 6, 2009 at 11:40 pm

I really liked this post Rusty. It is a very simple post, but its very good advice when for one trying to get back into a fat burning mode. I have to admit, i used to think i had to eat lots of pre and post workout carbs to have a good workout, but i have completely dropped that whole approach to working out. I definitely did notice the extra pop your muscle get, but at some point i felt to inflated. So now i try to go into working out as fasted as i can and i try not to eat right after either.

Keep up the good work!

Andrew

alex April 7, 2009 at 4:46 am

hey rusty

Thank you for another great post. I gain so much knowledge on how to take care of myself from your insights and for this i cannot thank you enough. Recently my whole school has been catching the cold. I want to work out, but i hear that it prolongs the sickness. I would love to see a post about how to take care of your body when you’re sick. Just an idea. Take care.

Dave April 7, 2009 at 7:13 am

Excellent article, Rusty. I’ve been advising people of this concept, and using this advice in my own weight loss journey, for awhile now. Simple is always best, as far as I’m concerned, when it comes to getting to your goals! And if you don’t get into cardio, I don’t think permanent weight loss is really achievable.

Dave.

Mike M. April 7, 2009 at 8:28 am

Rusty, this is a great, commonsense, logical article. Thanks for posting it.

Bryan April 7, 2009 at 9:34 am

Good article Rusty. I didn’t know that carbs could cause a couple of pound weight jump like that. Last Saturday night I had a bunch of pizza and then I finished it off Sunday morning. By Monday I’d gone from 170 to 173. Now today, I’m back down to 171.

How does eating carbs do this? Where does the weight come from?

Also, my wife is starting to come on board with the diet and working out after loosing about 15 pounds just from me doing the grocery shopping. (No more ding dongs in my house!) What do you recommend exercise wise for someone just starting who is pretty out of shape?

MrBunny April 7, 2009 at 10:01 am

Some how i don’t think that guy in the picture is concerned about a brief workout but rather maintaining a slow pace so he has a nice view in front…who can blame him, great photo as always Rusty.

Chris - www.fitnessfail.com April 7, 2009 at 10:37 am

If I’m reading correctly you seem to be asserting that you need to have your muscles be glycogen depleted to optimize fat burning?

What is this based on? Generally, high intensity interval work (HIIT style training) is at a high enough percentage of Vo2 Max that it will be fueled by carbs, no matter what. The body simply cannot adapt to burn fat at extremely high levels of intensity. Trying to do really high intensity work with depleted muscle glycogen is an excellent way to make the workouts lower intensity and less effective though.

By contrast, the lower intensity steady state cardio is less effective at depleting carbs, since it’s usually at a percentage of effort that can be fueled partly by fat oxidation.

I’m not arguing against HIIT – I think the benefits are excellent, especially in terms of “bang for your buck”, in terms of benefits to the cardiovascuar system for the amount of time spent.

Patrick April 7, 2009 at 10:44 am

Hey britkan the very broke student:
Get yourself a good light jump rope and do rusty’s jump rope workout consisting of 20 min intervals in sprint style, then do 20-30 of steady state by jogging outside. This is what ive been doing and it will kick your ass. your focus should be on jumping as if you are running as fast as you can, you will forget you have a jump rope in your hands. I think its a good idea to throw in marathon cardio when you feel like you need to. I like the idea of instinctive training, meaning listenin to your body and making the appropriate adjustments which correspond to your diet.
good one, thanks Rusty

David at Animal-Kingdom-Workouts April 7, 2009 at 11:22 am

The point you made about carbs helping guys get more of a pump in the gym, but this not translating into weight loss, was interesting. I’ve never heard of this before, but it makes sense. As far as cardio goes though I always believe short and intense beats long and moderate everytime.

– Dave

fitness-siren April 7, 2009 at 11:23 am

That is a new concept for me as well, Rusty! Although it sounds somewhat like cardio confessional, it makes sense when you explain it this way. I always have to keep in mind that the reason for the longer cardio session is for carb depletion and not to make up for a bad day of eating…LOL.

Helder April 7, 2009 at 1:43 pm

Training is a very individual thing in every way, and that includes cardio like you’ve pointed well in this post, people usually think about training as an individual thing when it comes to weight lifting and to nutrition.

I don’t like long distance running, besides i eat a low carb diet therefore HIIT cardio is the very best way to go in this case, i can tell by my own experience.

Unfortunatelly most advices we see on the net are still the one size fits all, or my way is the only way etc…

Again you’re ahead of things Rusty

John April 7, 2009 at 1:44 pm

Another terrific article. As I always tell folks, I had planned to start a fitness site with lots of great ideas . . . but then I found Fitness Black Book and it was already saying what I wanted to say!

I would add a couple of things:

1) BRYAN: Carbs = water. A binge of pizza can add fat . . . though probably not much if it’s just a 10-12 hour orgy. Water retention will add pounds of weight as well as contribute to the puffy look. The reverse is true. Deplete carbs in the diet and you’ll easily “lose” a few pounds . . . of water. Finally, the bulk of the food will add weight. How much does a pizza weigh? Shove it in you . . . while washing it down with a drink or two and your body weight will increase.

2) CHRIS – I agree with the article in that depleted glycogen will generally = more fat burning. It is, also true, however, that your liver and muscle glycogen stores can be fully topped off and yet with correct exercise you will still burn fat. Both are true. I think it comes down to a matter of degree.

A lot has been written about this when people argue whether it’s better to do cardio in the morning (in a fasted state). Here’s Tom Venuto’s opinion on the subject:

“First of all, morning cardio burns more fat! Early in the morning before you eat, your levels of muscle and liver glycogen (stored carbohydrate) are low. If you eat dinner at 7 p.m and you eat breakfast at 7 a.m., that’s 12 hours without food. During this 12-hour overnight fast, your levels of glycogen slowly decline to provide glucose for various bodily functions that go on even while you sleep. As a result, you wake up in the morning with depleted glycogen and lower blood sugar – the optimum environment for burning fat instead of carbohydrate. How much more fat you’ll burn is uncertain, but some studies have suggested that up to 300% more fat is burned when cardio is done in a fasted, glycogen-depleted state.”

Arya -weight loss blog April 7, 2009 at 2:48 pm

Great post Rusty! It’s definitely easier to get back in the fat burning zone this way.

Thanks for answering my question on strength training. So when you say you perform a routine for 9 months out of the year is it the same exact routine with the same reps and exercises? My current lifting routine is
day1 – chest back
chest – incline barbell 3-4 sets 3-5 reps
incline d-bell 3-4 sets 3-5 reps
flat bench d-bell 2-3 sets 3-5 reps
back – chin ups 4 sets 3-5 reps
lat pull down 3 sets 3-5 reps
long bar row 3 sets 3-5 reps
day 2 shoulders bi’s tri’s
shoulders – seated d-bell press – 4 sets 3-5 reps
seated barbell press – 3 sets 3-5 reps
lateral raise – 3 sets 3-5 reps
bi’s – wide grip Olympic barbell curl 3 sets 3-5 reps
preacher curl 3 sets 3-5 reps
incline d-bell curl 3 sets 3-5 reps
tri’s – close grip bench 4 sets 3-5 reps
dips – 3 sets 3-5 reps
rope pull down 2-3 sets 3-5 reps
I hit each muscle group twice per week. So could I hypothetically perform this exact routine for 9 months straight as long as I am still making gains? In other words is it ok to perform the same number of reps and sets for such a long period of time? I remember in one of your posts you said there are times when you perform lighter weights and heavier weights and also that your rep range can range from 3 to 10. Thanks for your patience with all my questions and long posts

Chris - www.fitnessfail.com April 7, 2009 at 3:48 pm

John –

The effectiveness of morning cardio on an empty stomach continues to be debated. The evidence is pretty conflicting here, and I’m not going to touch that issue. Advocates of this approach are almost always arguing for lower intensity steady state cardio – since this is the range that can directly oxidize fat as a fuel. However, this approach to dropping fat has really fallen out of favor lately.

It’s irrelevant though – HIIT does NOT burn fat as a substrate. The intensity levels are too high. Sprints and the like by necessity rely on anaerobic metabolism and stored muscle glucose. What they DO do is have a myraid of benefits to the cardiovascular system, evoke a favorable hormonal response, and burn (some) calories.

I’ll quote Lyle McDonald here:

” And the logic is 100% sound right up until the last part of it
“…thus lose more fat.” A fundamental mistake that’s been held by researchers, physiologists, trainers and coaches for decades is that ‘burning fat during activity = fat loss’. You find the same argument in the ‘do low intensity activity because you burn a greater percentage of fat’ folks; their logic that burning more fat during activity = more fat loss.

The problem (well, there are many problems) is that they are focusing only on what’s happening during the exercise bout. That is, they are worried only about what’s being burned during the 30 minutes of activity. That’s problem #1: what about the other 23.5 hours of the day? Most (but not all) studies have shown that, when you look at total fat use over 24 hours in response to activity, the body will figure it out. For example, if you burn more fat during exercise, you tend to burn less fat the rest of the day; if you burn more glycogen during exercise, you burn more fat the rest of the day. Over 24 hours, it balances.”

Trygve April 7, 2009 at 6:43 pm

to achieve maximum weight loss, is it a must to have depleted glycogen stores? so u have to feel bad to loose fat? im so confused since ive been like yo-yo dieting for quite some time and never been able to get to my weight goal and fat % goal. What type of eating do you guys with 6-8% and you rusty use? i want to be able to play soccer well also and dont run around with depleted glycogen stores and not been able to

Yash April 7, 2009 at 10:50 pm

Chris,
HIIT is indeed fueled by glycogen and carbs, but part of the effectiveness of HIIT comes from the way it releases fatty acids into the bloodstream during high intensity. This is why a good morning HIIT session followed by lower intensity cardio can be so effective. Not only are you burning what you just released when you do the lower level cardio/activity, but you have primed yourself by making sure you are naturally in a lowered carb state. Also, caffeine not only gives a low calories energy bump, but it has been linked to increased fatty acid release. most of that is from research and studies I’ve found. [meaning the rest of this, I’m speaking with a little less scientific backup]
Now, going along with the point you just made, even if you forgo the low level activity after HIIT, fatty acid release and a metabolic pump will help you burn more fat through the day. One of my own random musings has always been that, I know HIIT increases your metabolism. I feel like when I do it later in the day, it is slightly wasted, because when you sleep you metabolism naturally slows. I don’t know if it’s true of not, but I’d imagine that if your HIIT was in the morning, you’d have a full day’s boosted metabolism, rather than just that period before bed.

On a side note, I don’t know if you caught my response to one of your comments a few posts back, but I enjoy your comments. It gives me a chance to flex my nerd muscles, which don’t get used as often as my physical ones.

Chris - www.fitnessfail.com April 8, 2009 at 8:34 am

Yash – I must have missed your comment if I didn’t respond I missed you comment. Glad someone enjoys my rambling though, I don’t want to come off as an overly argumentative exercise phis. geek 🙂

To respond to your post:
I do like the caffeine boost, though I drink more than I should.

I’m not sure on the post exercise burn from HIIT. I believe you’re referring to EPOC? Most of the science I’ve seen doesn’t support this effect being significant, but I personally always felt like there was some lasting effect after a workout. Anectdotally, if I start the day with some kind of cardio workout I feel more energized the entire day.

Mel April 8, 2009 at 5:29 pm

Rusty,

Been meaning to ask you this for a while but hadn’t mustered up the courage until now to speak it. I’ve been exercising pretty rigorously for the past year or so, doing lots of HIIT calisthenics + heavy lifting – often times 5-6 times a week. In the process, I’ve also tended to cut down on my food portions and have yielded to healthier options as well. The problem, since around this past fall, has been my lowered libido (I’m early 20’s) and I can’t pinpoint the exact reason for it, I have some of my suggestions and listed following are some of them: lower body fat %, over-training, not enough calories or the cold weather and how I feel incessantly cold nowadays – probably due to lower body fat).

Have you experience anything like this? It is kind of depressing. Thanks

admin April 8, 2009 at 6:19 pm

Adam,

Nice post on explaining MetCon.

rugby,

You will have to adapt to your circumstances. I have seen people get incredibly fit regardless of their injuries or conditions.

BurritoKid,

I like to do quick intense exercise at the end of fasting, but will add in Steady State if I still feel a bit carbed up.

britkan,

You should do HIIT followed by steady state cardio and see how that works first, click the “low body fat” link at the bottom of my site. I also have an example of a body weight circuit I used to stay lean without going to the gym. Click the “Body Weight Training for Fat Loss Link” at the top of the site. That will be a good start.

Scott,

Sounds like a good plan. Bascially anything that can quickly get you back into fat burning mode is what you are aiming for.

Jeremiah,

Funny that you should mention eating a lot of calories before running a marathon. Although I am not an expert at all when it comes to running a marathon, I think those men and women do eat crazy amounts of calories leading up to the big race.

Yash,

Try rugby practice in a fasted state and adjust from there. It is tough to give you an exact answer because there are a lot of variables involved. As far as feeling carb depleted…I can tell when the muscle look a little bit flat…you basically look a little smaller than normal (not in a bad way). What I like about this is that it really allows you to see how much fat you have to lose. People that are carb loaded all the time, get an unrealistic idea of their body composition. If you can look good carb depleted, you will look outstanding when it comes time to hit the beach, or go on vacation.

Andrew,

You will experience great fat loss results over time if you stick tih this approach.

alex,

I follow this rule…a head cold I will do low intensity workouts (maybe just strenght training without cardio or limited cardio). If it is a chest cold…avoid working out alltogether.

Dave,

There are some poeple that stay lean without cardio, but typically there is some “type” of interval activity involved (like circuit training, which to me is like doing cardio with weights). Sticking with a really rigid diet can do the job, but who wants to do that? I like the ocassional beer and pizza too much 🙂

Dave – Best Ways to Lose Fat

Great blog you have started….Thanks for mentioning this post. I subscribed to your RSS feed.

Mike,

Thanks…Just another tip to implement if it fits in with your strategy.

Bryan,

A simple explanation…the carbs just make you hold more water weight for the most part. Good deal with your wife working out now as well. As far as recommending a workout…It depends upon her weight and condition. The biggest thing is to get her in the gym and teach her some really basic easy-to-remember lifts for each body part. Have her do things she is comfortable with. The biggest problem I see with many personal trainers is that they take people WAY outside of their comfort zone. Remember, since she is a beginner, almost any lift that she does is going to produce results. So a basic 2 day split routine followed by 20 minutes of cardio to begin with…4 days per week in the gym total. After a month you can introduce HIIT (walking followed by fast walking at first…she can jog when she feels comfortable). A good diet and slowly improving without quitting is what is going to ultimately work for her.

MrBunny,

You are bad (but right)!

Chris,

Good points. When I’m talking about marathon cardio…I am suggesting an intensity that is higher than the low intensity fat burning cardio that 99% of the people in the gym do exlusively. I like to do HIIT in a depleted state to release fatty acids into the blood stream. True that the body can’t burn fat at that high intensity, but that is why I tell people to followup with low intensity steady state cardio to utilize the fat that is released from the higher intensity training.

Partick,

Perfect advice. I haven’t hit the jump rope for a while. I may begin to do that routine I outlined again to prepare my body for volleyball this summer.

David,

I agree that the tough intense cardio is much more time efficient. I also believe that this marathon cardio is more of a way to “put the body back on target” to burn fat…basically to get the body to respond better to the intense cardio (which is where the real fat loss results happen).

fitness-siren,

Just another way of looking at cardio. Something to pull out of your “bag of tricks” if fat loss comes to a halt and you want to get a bit leaner.

Helder,

Thanks buddy…every post I do is typically a tip that someone can try if they are stuck. Out of the hundreds of tips on the site, people can test and tweak until the come up with the perfect routine for their circumstances and goals. There are so many variables at play that it would be impossible for me to come up with a one-size-fits-all routine.

John,

You should still start a fitness site! If you do, make sure and contact me…I’d love to help you get started. There are a lot of people interested in this topic and not enough quality sites to cater to these people. My goal when I started was to improve the internet a bit and the more helpful websites that get launched, the better.

Arya,

Your routine looks good. What I would recommend is to keep doing this exact routine until you fail to make progress. At that point, drop one exercise per body part. So now you are just doing 2 exercises per body part. Do 5 sets 3 reps of each exercise once you are down to just 2 exercises. This will lower your volume but allow you to focus and increase the tension more (which will put you back in strength gain mode). As far as lifting lighter. I do it on those days when I’m not “feeling it”. Some days you go into the gym and the bar “feels heavy” in your hands. On those days, do the exact rep range with MUCH less weight. So if you could normally do 5 sets of 3 reps on the bench with 225 pounds…do 5 sets of 3 with 150-185 pounds. Make sure you lift at the exact same tempo as when you are lifting 225. This is a way to train your nervous system for maximum output while giving your tendons a break.

Trygve,

You can lose fat up to a point without depleted glycogen stores, but it you want to get exceptionally lean…this is what is going to help get you there. No need to go overboard…if you are playing soccer you are naturally going to burn up a bunch of glycogen in the muscles aprt way through the game and then be in good condition the remainder of the game without feeling bad. Just aim for a balance.

Yash,

I love the “nerd talk”…both you and Chris do an excellent job of explaining your points. I always look forward to reading the communication in the comment section. It is better than the posts a lot of the time!

Chris,

As a Seattle guy, I don’t believe there is a thing as too much caffeine (kidding)…I am a fan though!

Mel,

You may want to dial it down a notch (4 times per week and shorter workouts). A lower libido is a big sign of over-training. Also, you should increase your calories a bit. You should feel an increase in libido and your body should feel “warmer” than normal. You are paying too high of a price to get in shape (I did a similar thing when I was starting out). You have a lifetime of working out ahead of you, so don’t push so hard in the beginning. Stay somewhat lean and consistent and over time you will get in better and better shape.

Good comments!

Rusty

Anthony April 8, 2009 at 11:24 pm

Great post Rusty! Thought provoking as always. I like the Google friends thing you have now as well.

I was just wondering, for a dude like myself who wants to get a little bigger but cut up (obviously following the common aesthetic of this site: Hollywood and not body builderish), would I also have to watch my carbs, like, all the time? I usually remain pretty lean just because of how my body is, and I exercise regularly, but I definitely know about the pump you’re referring to. I’m Italian so I eat a good amount of bread, pizza, and pasta, not to mention regular cereal intake. I stay away from junk food most of the time, and I eat healthy and well-balanced meals.

I can usually do cardio exercise for long periods of time, so I can’t say that I am depleted in terms of diet. Just today I played basketball for 3 and half hours, but I definitely like your opinions and viewpoint as I respect your knowledge and focus on the same physical type that you advocate.

Side note: those crazy 8 body circuits literally turned my legs to jelly on Monday. I couldn’t move after 2 sets.

Thanks in advance man and keep it up!

John April 9, 2009 at 12:02 am

Chris – let’s take sprinting as an example.

A sprinter will rely on fast twitch fibers primarily and these are anaerobic. So in theory, I agree with your statement: “It’s irrelevant though – HIIT does NOT burn fat as a substrate. The intensity levels are too high. Sprints and the like by necessity rely on anaerobic metabolism and stored muscle glucose.”

But . . . in the real world . . . the sprinter will be recruiting both fast and slow twitch fibers . . . if not during the actual “sprint” then at the start and end of the sprint, the warmup, walking on the track, recovery and so on. In fact, he’ll use some slow twitch fibers even while he sprints.

So in practical terms a HIIT session will burn fat . . . even though in a lab we might show that the anaerobic effort of fast twitch fibers is relying on glucose.

But there is a second aspect to this discussion which is very important and that is whether the trainee is in ketosis and thus using fat for fuel.

In ketosis, if you were to sprint in the morning, then fast all day, you would still be able to sprint in the afternoon . . . though perhaps at a somewhat reduced level of intensity. This is because the muscles have adapted to burning ketone bodies for fuel.

Lyle McDonald has written what I think is some of the “cleanest” articles on the subject of ketone bodies fueling HITT so I will defer to his explanations.

Kash April 9, 2009 at 1:51 am

a Very interesting and helpful post. ironically after all the carb-related articles i have read recently i just had to go on a 2 day carb binge earlier this week…. another thing i find VERY good about the idea of doing a long strenuous cardio session, is i find eating “low carb” or atleast reduceing your carb intake is like a steam roller…. you start out slow and take awhiel to get going, but once you have your momentum in the right direction, its easy to keep going, nothing will stop you! but at first, you always have those “carb” or “junk” craveings. Another thing i adapted was having one junkfood or carb day a week. this allows me to not feel like a fanatic, and reward myself for all my hard work… At the same time guilting me in to working hard physically and dietarily all week!

Chris - www.fitnessfail.com April 9, 2009 at 10:29 am

John – I’ll have to look those up. I really like Lyle’s stuff, since I think he’s pretty good at checking his sources and not buying into psuedoscience.

I’ve had issues with ananerobic work during low carb diets before, but they were not full on ketogenic diets. I’m not aware of any studies (even informal ones) about anaerobic work while ketone adapted. I’d be really interested in seeing this, since I think it’s something that isn’t addressed in the mainstream exercise science literature.

The focus of the mainstream stuff is really on either o-lifters of endurance runners… which is something I’d like to change.

BurritoKid April 9, 2009 at 11:54 am

I think this is Craig’s whole approach now though, he is mentioning to forget about the whole “fat burning” zone approach and is going for burning carbs through resistance and intervals. This is turn will burn more fat later.

I found it kinda weird in the wording because everyone is advocating burning fat with workouts, even he at times. Now he is going about it this way. I think his main point is the myth of the “fat burning” zone though.

James April 9, 2009 at 2:24 pm

BurritoKid,

I think your spot on. Intervals and weight training will deplete glycogen, theoretically enhancing fat oxidation thereafter. However, none of this matters if one is not in a caloric deficit.

The caloric deficit is the key to weight loss. Macronutrient composition has the potential to alter the %’s of what’s lost (fat or muscle), but that’s even speculative with few, if any, studies indicating one diet if optimal over another (assuming fat loss is the goal and caloric content is identical – then again, higher protein diets should MARGINALLY improve calorie burning from thethermodynamic benefits of digesting the food and also potentially improve muscle retention).

John April 9, 2009 at 9:27 pm

Chris – About your comment: “I’m not aware of any studies (even informal ones) about anaerobic work while ketone adapted. I’d be really interested in seeing this, since I think it’s something that isn’t addressed in the mainstream exercise science literature.”

I can vouch for the fact that after about 2-3 weeks, you will experience pretty good energy levels that will allow you to set new records. I do low-carb diets (50 grams or less of carbs for 5-10 days) while using EDT (Escalating Density Training) and am able to increase reps.

I would caution anyone, however, that the first 2-3 weeks are no joke and you would be best served using lighter weights for more reps. When I first start a low carb phase (like I did last February, for example) I just rowed, alternated with Heavy Hands and kettlebells. Hitting a heavy bag and body weight exercises are also good.

Chris - fitnessfail.com April 13, 2009 at 11:12 am

John –

Heavy lifting is (mostly) ATP/PC based – that’s probably fine in ketosis if you allow adequate recovery between sets. I’m referring to circuits involving constant work (some heavy lifting, some body weight) for around an hour. My HR is generally > 150 most of the time, and I’ll be pulling loads anywhere from “really light” to around 85% of 1RM.

They generally consume around 6-800 calories.

When my carb intake is low, I can’t make it through more than about a 35 minutes on one of these without having a serious bonk.
But I also don’t eat REALLY low carb, they’re usually around 20-30% of calories for me, I just sometime have a low day.

If there IS an adaptation that would support this kind of workload I’d be really interested.

admin April 13, 2009 at 4:09 pm

Anthony,

Feel free to eat carbs and Italian food, etc. You have to live life. Just try to time the carbs in a strategic way at least part of the time. Google Friend connect is kind of in “beta” right now and I believe it will be much larger than Facebook. I have seen some behind the scenes things not released to the general public.

John,

Great point about fat loss. I love it when you guys “dig deep” into these subjects.

Kash,

I agree with you point about going low-carb. It becomes easier the longer you do it.

Burritokid,

Burning calories is where the majority of results happen, Craig is right. I just like to hit fat from every angle possible. Over time, this makes a big difference.

James,

Yeah…calorie deficit is a given if someone wants to lose body fat. Completely agree.

Good stuff guys,

Rusty

myra April 14, 2009 at 4:34 am

Hi Rusty

Hey im doing that already! Trust me guys and girls this really does work. I also, like you said Rusty, have a longer and more intense cardio session after pizza etc, combining HIIT and lower state cardio. I tell myself after ive “splurged”, i need to work hard to burn it off. if i dont do the cardio thing the next day i actualy feel sluggish and that bit heavier which as you know to a gymmer, is crap!!!
Well done Rusty, you hit the nail on the head yet again. good to know im in the right direction. take care.

Tyler April 20, 2009 at 1:28 pm

Rusty,
What amount of carbs in a diet would create a carb depleted state? John’s last post said that he consumed 50 grams or less of carbs for 5-10 days. In this style, is the small amount of carbs referring to complex carbs (breads, pasta) alone, or complex carbs and fruits? Thank you for your help.

Andrea May 6, 2009 at 12:45 pm

I completely agree! Although for more practical reasons, I kickbox and it never feels good to spar with that “heavy” feeling your body gets with carbs!

John July 28, 2009 at 11:09 am

Doctor-supervised hormone injection weight loss program: $2500

Six months of Nutri-System: $2000

The latest crappy exercise equipment sold by infomercial: $500

Adjusting cardio to diet: PRICELESS!

Me March 22, 2010 at 5:27 pm

Hi!

I have a question about the best muscle (!) burning exercises. I’m 1,75m, 82kg, 22 (woman), but I’m not fat as one might think although my weight should be around 60-65kg. I don’t know what I’m doing wrong but although by long term jogging in the morning I feel slimmer and I’m getting rid of fat, I can’t get my weight down. Is it because I eat a lot of proteins or maybe I need another type of exercise? I don’t eat more than I burn! How could I lose overall body mass?

Thanks,
Me

Niko - noeXcusefitness January 15, 2012 at 8:15 pm

Great review of the different types of cardio and when they should be used. Like you say there is no one size fits all when it comes to cardio for fat loss. Personally I have been trying a combination of HIIT, Crossfit and Weight Training to attain a 9% bodyfat percentage. I have been posting all my workouts here noexcusefitness.com.au…training for those that are interested.

Hillary Coates August 14, 2012 at 4:10 pm

Rusty,
This is awesome info. Thanks. I just pigged out on toast and oatmeal because I had too many carbs yesterday. I know I’m carb depleted because my carb cravings are completely gone. Now i know I can get back on track quickly without days of agony.
One question for you:
How frequent should one perform HIIT? I do it 6 days a week for 10 min and either follow it up with my 1 hour of weights or 40-45 min of steady state cardio. Any more than this and I get really crazy grumpy.

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