Thursday, May 29, 2008

Improving Fat Oxidation

Part 1: What Science Says....

The pic above is of yours truly following the completion of the Triple T triathlon in Ohio this past week. The photo was taken on the last day, after about 5K of swim racing, 190K of bike racing and 43K of run racing. I was a little depleted to say the least (G can attest to that by the way that I was walking after the race :-)

My strategy for the race was (I thought) a pretty conservative one: Hit the prologue pretty hard (about 90% of max effort), take the second day, 2 olympic distance races, as a regroup day by racing steady (150 heart rate cap) then try and race day 3 at mod-hard, which is just a notch below where I would race a fresh half (mod-hard to hard). I discussed G’s race plan with him in the car. He wanted to shoot for the lead early in the prologue and first oly. So, basically, his plan was to go hard from the gun. As it turns out, he had to continue to go hard pretty much until the last run in order to ensure the W. When I say hard, I mean hard in every sense of the word. Physiologically, if he were to go any harder he would be limited by lactate accumulation in the same way that an 800m runner is. G was racing very close to his max all weekend long. So, how did my conservative strategy play out? Great, until the second lap of the bike on Day 3 when I dropped from holding 280W to less than 200W in one fell swoop. Bonktown, population…me! Fortunately, my stupidity was transient. I went into damage control pretty quickly when I saw the writing on the wall. The second lap of the bike was very easy (13 minutes slower than the first) and by the time the run came around, I had a little bit of steady back to play around with. Yet again, the gap between G’s performance and mine became Grand Canyonesque as the race duration increased. I was forced to race so far below my max in order to just survive the weekend, while G was able to push his max day after day. Why? My arch enemy, Captain Fat Oxidation rears his ugly head again.

This post is going to be a little different to my previous posts on fat oxidation. Hopefully by now, you’re as convinced as I am that the ability to utilize fat as a substrate is an important, distinguishing factor between those who excel at Ironman and those who, despite impressive short course results, are unable to put it together for ‘the big one’. Hopefully, you’ve already contacted Matty Stein and booked a testing slot at our Endurance Corner lab in Boulder to determine whether fat oxidation is limiting for you. No, this post isn’t for the fence sitters waiting for academia to catch up before making a decision as to whether to devote their time toward improving this physiological variable. Nope. This post is for those athletes who have gone through the testing, identified that fat oxidation is a limiter and who are ready to roll up their sleeves and get to work on turning yourself into a fat burning machine.

So, this first post is going to give you a little background reading on what science says about means and methods to improve your ability to utilize fat as a fuel. My next post will be entitled “Fat Oxidation….What Big A says” and will profile some of the improvements that I have seen in my own athletes and the training and nutritional methods that we have used to achieve them.

But first….

You know how most folks have a favourite actor or actress? An actor that, if they come out with a new movie, you just have to see it? Well, in the same way that you may be a huge fan of your favourite movie star, I am a huge fan of a sports scientist by the name of Julia Goedecke. Julia’s chosen ‘genre’ is the influence of fat oxidation on long distance racing performance.

Julia and her colleagues at the Sports Science Institute of South Africa conducted a study in 2000 that looked at individual differences in fat oxidation across a variety of exercise intensities (rest, 25%, 50% and 70% VO2max). She came to a number of conclusions that have practical implications for ultra-endurance athletes:

#1. There is a wide variation in the amount of fat that is oxidized at rest.

Some of the athletes were deriving almost 100% of their resting energy from fat, while others were only deriving 25%. This has HUGE implications on athletes who struggle with body composition. By increasing your rate of fat oxidation at rest, you could potentially lose body fat 4x faster than you currently are!!! Not to mention preserving your precious glycogen stores for your next training session.

#2. Those subjects who burned more fat at rest also burned more fat at ALL EXERCISE INTENSITIES (see chart)

Even at 70% VO2max, some of the subjects who were 100% fat burners at rest were still deriving 40% of their energy from fat (think G), while in the athletes who were poor fat burners at rest, fat burning had completely shut down (think me, or you??)

So, what were the distinguishing factors between the ‘corvette’ athletes and the ‘prius’ athletes? Interestingly the factors changed somewhat with increasing exercise intensity.

a) The concentration of Free Fatty Acids within the blood

This is THE pre-requisite for fat burning at rest and all exercise intensities. In other words, if your blood is full of glucose as opposed to FFA’s, you will not be providing the muscles with any stimulus to ‘learn’ to use fat as a fuel. High FFA levels (and low-moderate blood glucose levels) are a pre-requisite for fat burning. This has LARGE nutritional implications. If you keep your blood sugar levels perpetually elevated, you will never become a fat burner. Period.

b) The concentration of fat-burning enzymes within the muscle.

While short chain and medium chain FFA’s can diffuse into the mitochondria freely, long chain FFA’s must ‘hitch a ride’ with the enzyme carnitine palmitoyl-transferase in order to make it to the mitochondria. A shortage of this enzyme will mean that even if you have sufficient FFA’s within the blood, the long chain ones will be left by the side of the road with their thumb in the air waiting to hitch a ride. This enzyme is inhibited in the post absorptive state when blood glucose is elevated.

c) Mitochondrial content within the muscle.

Of course, in order for FFA’s to be ‘burned’ and used for fuel we need a sufficient number of ‘engines’ to burn them. In this sense, the number of mitochondria within the muscle can ultimately limit the rates of fat oxidation. This is a function of aerobic fitness, which in turn is a function of the number of contractions performed by each muscle fiber, or put another way, as my buddy Chuckie V is fond of saying, miles make champions.

So, there you have it – 2 simple ways to turn yourself into a fat-burning machine:

1. Cut sugar from your diet (and moderate total CHO intake)

2. Train MORE in your aerobic zones (cut out the hard stuff until you’re ready for it).

Not exactly earth-shattering revelations, but based on what we are seeing in the lab these 2 principles are not being applied by most athletes. You can beat a large portion of the field by making these simple (though not easy) changes.

I’ll get down to more specifics in the next post.

Train smart.


Benzing asks:

“I have been tested and my suspicions confirmed that I am about as inefficient as possible. Is there any data on how long it takes a 44 old female body to retrain itself when practicing the prescribed training and change in diet?”

There has been a good amount of research on the physiological effects of low and moderate carbohydrate diets (e.g. Ravussin et al, 1985, Weinsier et al, 1992). Generally speaking, individuals who adopt a low-moderate CHO diet can expect a change in their resting RQ of ~.05 within 12-16 weeks. This translates to an increase in resting fat oxidation of ~20%.

The extent to which this carries over to performance during exercise is dependent on your overall fitness, or how many ‘engines’ you have to process your new found fuel line. This is the reason that studies looking at the impact of training on fat oxidation have returned mixed results. Keep in mind however, that even for the relatively unfit, burning more fat at rest is still a good thing!!

The vice versa argument also applies, as we found while driving the Sportsmobile back across the country from the Triple T. You can have the largest capacity tanks and the biggest engine around, but until you pay the lady at the gas station and she turns the fuel pumps on, the number of miles that you’re going to be able to drive is severely inhibited. :-)


firepotter said...

excellent post!

ckotte said...

Alan - once again...great post....if I ever get to Denver...I will make sure I get my fat tested!

Also - it was nice to meet you at the TTT (I was Chuckie's athlete)..

See ya around.


Alan Couzens said...

Thanks Chris.

It was good to meet you too.

Hope recovery is going well.


Paul Fleuren said...


Thanks so much for this. This is exactly what I have been wating for.

I feel like I'm swamped with information on the 'why we need to..... blah,blah' but the resources that are available on the actual 'How to.... blah, blah' is limited.

This is gold and it clearly explains how to.

Alan Couzens said...

Thanks Man.

Must say I'm guilty of that. Much more a "why" guy than a "how" guy.

I guess there comes a point that you've just got to roll up the sleeves and get into the nitty gritty.

Thanks for the kind words.


Unknown said...

Alan, Thanks for the post. I second Paul’s post. There is lots of info on the why side not so much on the how to/practical side. I have been tested and my suspicions confirmed that I am about as inefficient as possible. Is there any data on how long it takes a 44 old female body to retrain itself when practicing the prescribed training and change in diet?

A said...


Great to see you at the TTT. I never got the chance to introduce myself--although I was the one screaming for hot chocolate to you guys on Saturday night after the prologue. I was darn cold after that race.

Two things I would like to point out. First, the openness of your dialogue and data is appreciated. Open source/free source info is wonderful. Second, I feel that you're making your mark as one of the sport's premier scientist. Keep it up. Finally, I look forward to the day when you have enough data to write a book. Blogs are great, but eventually you will have enough gold to put out a solid book.

Matthew Amman

todd luther said...

What a concept! Scientific data for the masses to absorb.

This is hands down in the top 10 useful writings I have ever read.

Great stuff. Thanks Alan

Ward said...

Great post. Really found it interesting of the large range of fat oxidation during rest. Have you found scientific publications finding similar results - if not you should think of forming a collaboration with someone to get this data published.

Alan Couzens said...

Thanks Matthew.

I think we could have made a lot of dough selling hot chocoloate that night. :-) It was brisk!!

The book idea is definitely on the horizon. There seem to be a lot of good single sport books out there, but, with a couple of exceptions, not a lot of good scientific books out there on triathlon training.

I really appreciate the encouragement.

All the best,


Alan Couzens said...

Hey Benzing,

Very good qu.

I updated the main post with some thoughts.

Best regards,


runtilyoudrop said...

Thanks Alan, A good paper on fat zones and enough to get me thinking on my diet. Looks like I am gonna have to give up the sugar, which my dentist will like.

Whay about energy drinks on long rides? Or should it just be water?

David McCullough said...


I get the importance of training in the correct aerobic zones, and have personally seen the benefit of Mafetone's philosophy? The thing that I am unsure of is the nutrition component. It seems that you need a large number of carbs each day, 60%, to maintain the level of training necessary for endurance workouts? Am I missing the point when you say we need to limit carbs in our diet in order to use fat for fuel, even at rest? Or is it simply a matter of eating quality carbs, mainly fruits and vegetables.

Thank you for the great information and insight.


Chuckie V said...

As you state Alan: there's no earth-shattering news here but you put it in a way that appeals to us simple folk: Cut sugars, slow down a little (when the time is called for) and listen to your body.

To these, I'd add: warm-up thoroughly, add volume where appropriate (and it's almost always appropriate!) and expect that any desired results will take a long time to develop and display themselves.

All the world-class athletes I know (quite a few, actually) took a long time to get good, and almost all of them did it by way of this simple "approach". Others might simply claim that it was "talent" that got them there, when in reality it was WORK. It takes work to be patient and eat right. Talent lies.

Alan Couzens said...


First of all, congrats on Lanzarote. Despite your disappointment, 6hrs on that bike course is pretty quick and (more importantly) it looks like you put together a solid run after.

Yep, you need sugar during long training sessions and immediately after but that's it. No other time! The rest of the day, it's caveman all the way.



Alan Couzens said...


The macronutrient composition (%) of the diet is highly variable. The 60% that has been touted in most sports nutrition texts may be applicable for fairly elite/high volume athletes during their race prep phase.

I would recommend starting with ~150g/hr in the base phase. For an athlete training 2hrs per day. This is 300g/day. On a 3000kcal/day diet, this would amount to 40%CHO. For a 3hr/day athlete 450g/day would probably yield closer to 50%CHO/day.

Hope this helps.


Alan Couzens said...

Hey Chuckie,

Agreed. It's a bit of a paradox that in order to truly discover your 'talent' you're going to have to put in 10000hrs of work in order to do so :-)

After doing this coaching (and athlete thing) for a relatively long period of time, I have a firm belief that, while their is a small range of inter-athlete variability, fundamentally, you get what you deserve. Right now, I am a 17hr/wk athlete and I am getting what I deserve. I am confident that when I graduate to a 30hr/week athlete, in the years to come, the trend will continue.

A sport where you get out of it what you put into it? Gotta love that!


Unknown said...

In the blog you say:
"Some of the athletes were deriving 100% of their resting energy from fat, while others were only deriving 25%."

But the paper you quote says:

"The relative rate of fat oxidation at rest ranged from 23 to

So maybe you could correct your text.

The full-paper can be found here

Ward said...

Jasmine, thinks for the link to the reference. I was scouting for the article.

looking forward to the next in your series on fat burning.

tacxuser said...

Very interesting post.
But how one knows how much fat is one oxidating during an effort?