Burn the Fat for better Endurance & Health

by Mark Wolff


Sunday morning 7:30am my alarm goes off and that signals my time for a long training run. Today’s goal is around 2.5hrs which should give me around 33-34km’s at a comfortable pace. An easy no complicated morning preparation involving a nice hot cup of green tea, running shoes on and off I go. Around 11am my session is complete a comfortable 33km run and feeling good. Only now is it time for my first meal of the day.

“Wait a minute” I get asked. “How do you get up so late, don’t eat anything at all then run that distance at that pace comfortably without any need for fuelling before or during???” My short answer is that I am fat adapted. I am predominantly in a fat burn mode, meaning I can go a lot further on less. Whether it’s a 42km training run or a 180km training ride, at the right pace one can go for hours on his natural fat stores if properly trained. If you think about it in terms of motor vehicles, some vehicles require huge amounts of fuel to power them over distance while others are so fuel efficient they pretty much reach the same destination at the same time just on much less.

Over the past 20 years a huge legacy of massive carbohydrate fuelling has been entrenched in the latest generation of performance athletes. However more and more this is being shown to be less of an importance to making the body more fat efficient to be able to maximize the use of natural fat stores for fuel and rely less on carbohydrate intake in order to gain a massive performance benefit in a long endurance event. I often use the Kenyan or Ethiopian marathon runner as an example of this. A predominantly high carbohydrate diet, topped up glycogen stores and a 20km/h average speed for a marathon is all in order, for a 2hr performance that is.
Then we take a look at something like a Two Oceans Ultra Marathon where course record money is up for grabs and the Kenyan & Ethiopian runners appear with force to match their speeds against the Lesotho, Zimbabwean and South African ultra-runners. They just don’t stand a chance at least for now. The ultra-distance runners are so much more adapted to running at a higher pace on less. Yes, far more fat efficient athletes who spare glycogen on fat fuelling and go further on less.

As performance requirements demand more time so does your energy system need to be completely adapted to that time. Topped up glycogen stores are completely limited even if slightly spared with carbohydrate intake so yes smashing out a very high pace for a short space of time is perfect when it comes to carbohydrate fuelling. However the longer the event the fact is the more the fat efficient athlete will have an advantage. Let me just clarify that this doesn’t mean no fuelling on carbohydrates, by all means yes you should be, the brain will function far better on carbohydrate fuelling when the body is under stress and this will make a huge difference in performance however being fat efficient means you will require less than the average carbohydrate dependent Joe.

The Comrades Marathon which is a 90km Ultra run each year in South Africa has incredible winning times of around 5h30 roughly a 3:40min/km pace for this time over a course with huge elevation changes and lots of climbing. I have had the pleasure of working with some of the gold medalists (top 10) in nutrition advisory and on route seconding them. All race fuel is ready and prepped in various forms from liquid feed to food solids, gels and protein. Each year I measure intake of athletes on route in the form of carbohydrates, protein and fat as its being consumed along the route. What is quite amazing to see is that the elite runners actually consume anywhere between 20-40grams of carbs per an hour yet they still perform at an incredible pace. Most people I speak to are convinced these runners are consuming anywhere from 60-90grams of carbs per an hour, however this couldn’t be further from the truth. These runners run on their own natural fat stores and they are so fat adapted they are able to perform at a fairly high intensity with fat being their primary fuel source.

The next question is how do you become a fat burning machine of an athlete?
There are quite a few steps that need to be taken however most importantly is that it doesn’t happen overnight it takes time to become fat efficient and it takes effort and commitment but in the end you will reap the rewards.

Before we go into how to become an athlete that burns more fat for energy, let’s understand what it actually means. There are various physiological structures in the human body which can be “trained” to increase the amount of fat that is utilized for energy. Lipolysis is the process of breaking down subcutaneous fat and converting it into triglycerides which will ultimately be converted to energy and used by the muscles. This process takes time and there are other areas of fat which are more quickly accessible.  Upregulating Beta Oxidation, so that you can convert as much fat as possible and at the highest intensity as possible into Acetyl-CoA which of course is introduced into the Krebs cycle to allow for ATP production and fuelling of the muscles is one way. Also by increasing the amount of fat available to the body, to be utilized for energy not just in the form of ketones but in the form of intramuscular triglycerides is another way. In actual fact athletes can derive around 20% of energy from IMTG (intramuscular triaglycerol) depending on diet of course. Women generally have a higher IMTG than men and utilize more during exercise which begs the question are women generally more fat efficient athletes than men? Based on my experiences with female athletes I would tend to favor that opinion.

Increasing ketone levels is another way of providing internal fat fuel sources. However instead of worrying about being in a state of ketosis to make yourself a “fuel efficient” athlete, more steps should be taken to train the mitochondria to utilize more fat as fuel and this can be done in a non-ketogenic state. The focus should be training the body to convert fat to glucose to be used as energy internally without relying too much on external glucose sources. Many athletes try to shift into the LCHF (Low Carb High Fat) dieting phase to try to become fat adapted, however I don’t firmly believe this is where to begin. It’s a very difficult place to start if you are an athlete that suddenly wants to make this switch. I also get many people insisting on going into a state of ketosis without actually really understanding their own body’s requirements before doing such a thing and in many cases it’s not required.

Becoming a fat adapted athlete does require a key focus on nutrition. This is critical to any athletes performance however to make yourself a fat adapted athlete you need to start with your diet. There are some key points when selecting appropriate food types to make you more fat adapted and these are:

To Burn Fat you need to Eat Fat
This is a very important point. The general population fear eating fat, but in actual fact by eliminating fat from your diet you are limiting your body’s ability to be a fat burning machine. Introducing healthy natural fats into your diet is important to become more fat adapted. You don’t have to make huge changes overnight, but definitely have no fear of eating fat as it is critical to fuelling a fat adapted engine. Introduce a higher amount of fats into your diet in order to benefit from them. Medium Chain Triglycerides (MCT’s) are an excellent example of quickly accessible fuel in the form of fat which can be immediately utilized by the mitochondria as an energy source.

Carbohydrate intake needs to be Monitored
Fat adaption doesn’t mean cutting carbs it means being selective of the carbohydrates you take in. Dropping carbohydrates to under 50grams a day for most individuals will be an extremely difficult thing to do. I would suggest selecting carbs from more fibrous, low GI and vegetable based options as opposed to grains, breads and starches. It’s all about insulin management and by keeping insulin response very low you can be assured your ability to burn fat will be a lot higher.

Train the Brain
One of the biggest issue with carbohydrate limitation is that most people have a sweet tooth and are sugar dependent or tweaked to crave sugary foods. That’s one of the reasons why I am against “natural” forms of sweet such as honey. Yes, honey is natural however it is completely sugar and breaks down into glucose and fructose which means your brain is still trained to crave sweet and you are still playing with insulin. The same with sweeteners in coffee or tea or diet cold drinks, they might be low calorie but they are training the brain to stick with sweet.

Carbohydrate Timing
The timing and volume of carbohydrate intake is critical. If you wake up in the mornings and take in a higher carbohydrate meal, and then go and train you have completely mitigated your ability to maximize fat burn as you have already raised the blood glucose in your system which will be utilized as a source of energy before the body resorts to fat utilization. If the higher percentage of your daily carbohydrate intake is taken post exercise after a long or hard session due to the low insulin response you will again maximize your body’s ability to remain in a fat burn zone.

Over and above nutrition requirements there are other considerations that you should take into account when it comes to being a more fat adapted athlete.

Fasted Training
Training in a fasted state as mentioned earlier will definitely engage your body to utilize more fat as a source of fuel. By not providing any external sources of fuel, the body will have to adapt to relying on its internal sources primarily being glycogen and fat. Many people I deal with fear going on a session without an energy drink but if the session is 2hrs or under you will manage perfectly on water. If you are still very nervous to attempt it then take a sports drink with you and delay the consumption of it for the first hour in order to kick start the burn in that fasted state. The other option is to take a sports drink which does not cause a big rise in blood glucose so that you can still derive benefit for fat burn.

Training Intensity & Time
Something I need to stress is that training at an extremely high intensity can mitigate fat burn due to the fact that oxygen is required to convert fat ultimately for use as energy. In this case glycogen will mainly be depleted. However, training at a high intensity in a fasted state with shorter workouts and slowly building up will help train the body to utilize a higher percentage of fat at higher intensities and this has been shown in many fat adapted elite athletes. If you can talk while training then no need for high calorie drinks, sufficient oxygen is getting into your system to burn fat assuming you haven’t spiked your blood sugar. If you cannot talk at all during training and are puffing and panting then this is more your glycogen depletion state and these workouts should be kept to under 90min in a fasted stated and you can slowly build on them with time.

So with all this in mind what about racing? Yes we do race on carbohydrates, we definitely feel a great benefit from carbohydrate consumption even in lower amounts than the average person who is completely carbohydrate dependent. If our glycogen stores do deplete at some point in a long endurance event, for us fat efficient athletes it’s a transparent transition from glycogen to fat usage where no major pain or slowing is felt just a gear adjustment needed and the game goes on.

I could go on and on about the benefits of becoming a fat adapted athlete, it really doesn’t take much major effort just some healthy lifestyle, nutrition and training modifications and the benefits will be rewarded long term.

You may also like


Jonhurwi April 7, 2015 - 1:02 pm

MCTs for the win!
When I did my first full marathon I remember the countless ‘advice’ people gave me with regards to nutrition and carbo loading. The truth is keep it simple and clean. Your body doesn’t need extreme levels of carbs or sugar to perform.

Really awesome and informative article 🙂

Bob de la Motte April 7, 2015 - 1:53 pm

Fat is not all it is made out to be for the public at large. I ran consecutive Comrades Down runs of 5:30 and 5:26 on nothing but carbs. Caroline Worstman ate a potato en route to her 2014 Comrades Gold medal and won the Two Oceans 56km last weekend against a Russian pro. I eat protein, I eat meat and I eat all forms of carbs, fruit included. Moderation and listening to your body is the secret. For this reason when I have raced 250km single day alpine events (Dolomites) and competed in multi-day MTB races 8-9 days and ironMan, those events cannot be done on carbs alone. Protein comes into play. So in my book it is horses for courses and I can roll out endurance champion after champion who never touched fat en route to victory.

Mark Wolff April 7, 2015 - 1:58 pm

Bob I did say carb should be consumed during events and I do advocate protein but a fat efficient athlete has a big advantage and you most likely are a fat efficient athlete naturally being able to tap into your fat stores as required. Carbs in many people impact them differently from others you might be perfectly fine that way :-). I deal with all walks of athletes amateur to elite athletes and even though some of my athletes do take in a higher carb portion than some others they are still very fat efficient because of the way they train and the timing and volumes of their meals. The problem is that this isn’t the norm in today’s junk food ridden world where sugar has finally formed the foundation of the stable diet. So I guess it’s a N=1 each needs to didn what works for them. Boiled Potatoes are excellent for during the run dont spoke book sugar like a gel and would surely be an excellent source of natural food, I of course do advocate during an event I am a low carb eater but there is no way I would run a comrades or do and ironman on biltong :-).

Zama April 7, 2015 - 8:10 pm

I’ve been trying to be fat adapted , through LCHF since beginning Feb but its very hard for me, I have a weakness for fruit. Im not an experienced runner but Ive done a few half marathons and am training to do my first marathon later this year. I generally dont consume a lot of carbs, i dont use sugar at all . I eat eggs, fish, meat & veggies. Before my runs I drink coffee with butter & coconut oil & during the runs just water. The races Ive done I do end up drinking coke though. For the first time this past weekend I had my longest training run, 21km with just the usual coffee and water, 2.5hrs I know its slow but it was the first time I ran that long without coke. Didnt feel like I needed anything else. A few things Im wondering about. Im losing a lot of weight and Im worried because I dont want to, is there anything I can change in my diet to slow this down. I dont wanna end up looking like a skeleton . Im starting to wonder if Ive cut out too much carbs. I used to eat potatoes, sweet potatoes & fruit but have cut it out because I thought I need to be in ketosis to be fat adapted. As you can see I dont fully understand the concept but I spent a whole yr in 2013 reducing carbs & cutting sugar to lose weight so I dont want to go back to it. Basically Im looking for an alternative to carbo loading 🙈

Jonhurwi April 8, 2015 - 7:19 pm

Check this out by Dr Peter Attia, very relevant and even though its long, its well worth the watch 🙂

Blake Wilkins August 12, 2017 - 8:05 pm

Here’s my question on 12 August 2017: as a 70 year old athlete who still runs competitively (podiums in 10km and cross country but times at best reasonable) will it help at this stage to attemptto change now from carbo intensive to fat burning. Back in the day I was a 2:50 marathoner, 7;40 Comrades etc. nowadays, 10km in 47/48 minutes.
Blake Wilkins
Cape Town

Mark Wolff August 12, 2017 - 8:14 pm

Hi Blake very impressive resume 🙂 and the fact u are still going is very inspiring. I can just say this that as we age our bodies requirements change. We don’t produce testosterone like we used to when younger and carbohydrates as well as dairy actually become less tolerable. I would exoerienent with the nutrition to see what works best. Absolutely I would highly reccomend cholesterol foods such as eggs which aid testosterone production and if that was increased as well as protein then one would have to look at toning down their carbohydrate intake to prevent any infllamtion. Hope that helps.

Zama September 23, 2017 - 6:12 am

How do you know if you are fat adapted? I’m in no way an elite athlete but I’m an endurance runner. I try to monitor my carb intake but don’t really measure how much carbs I take it so not 100% strict. I always train fasted , never get hungry. Ran 2Oceans in water & 32gi endure only, never battled with hunger or energy…& I take almost the full 7hrs to finish 😂. I just did CTM , same thing. I didn’t struggle at all with energy, had water & 32gi endure. I’ve been told I could do so much better if I ate before or during a run (but I don’t want to mess with what’s working, besides, I’m not running for podium so an hr improvement really won’t do much) . If I “race” I usually do it on shorter distances but I warm up for around 15-20mins. I’ve always wondered if I’m really fat adapted because I doubt I’m in ketosis . I’m just a bit fussy about what a eat , just not all the time.

Tony Silva November 19, 2017 - 1:58 pm

Thanks for the Article Mark!
What is your opinion/thought on The toxins associated with very high protein and fat diets.
it’s effects on the health and performance of the athlete, i.e. Cholestrol etc. Though it’s been documented that high fats and protein diet is not the cause of Cholestrol, but rather the inability of someone to metabolise carbohydrates and that in this case carbohydrates is the cause of cholestrol. The fact of the matter is that in almost all cases where individuals are diagnosed with high levels of cholesterol and after 2 months of low fat diet their cholestrol levels do eventually drop to normal acceptable levels.
I personally stick to a balanced diet on a plate with approx. 30% protein, 10% fat and 60% Carbs with majority of it being vegetables and low glycimic index carbs. and low on starch. two to three portions of fruit daily and constant water hydration throughout the day.
Thanks for your blogs, i find them very interesting and thought provoking. Cheers.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: