Wednesday, 8 July 2015

The importance of fat metabolism in ultra running

Never has a topic, not just in ultramarathon running but in the nutritional world in general been subjected to a generalised pseudoscientific analysis as that of diet.

It is of course very natural for every athlete to contemplate and analyse every aspect of their training in order to improve performance and that includes diet. The chemicals that you put into your mouth ultimately translate into performance and it is natural to analyse what is the optimum combination of these chemicals that lead to a best performance in an event. But diet is not just about optimum performance; it is about generalised optimum health as well. The two are closely related as without optimised health there can of course not be optimised performance.

I will argue a case that a diet for optimised health is indeed a diet for optimised performance but that the diet during that optimised performance is actually radically different from the diet that lead to that optimised performance.

In the introductory sentence I mentioned that the subject of diet is one that has been subjected to more pseudoscientific (bad science) analysis than any other, not just in the world of ultra-running but in the dietary world in general. Body biochemistry is hideously complex with interplay of literally thousands of biochemical pathways, a symbiosis of which is a long way from being fully understood. It would be fair to say that at best we only partially understand these mechanisms and at worst completely misunderstanding them leading to practices that not only do not lead to optimum performance but that actually harm it and our general health in the process. I am not saying that these authors set out deliberately to mislead but when there is such a large interplay of a ridiculous number of parameters it is frighteningly easy to arrive at incorrect conclusions.

Bad Science
In writing this piece I will draw attention to the fact that I have a Ph. D. in science (Physical Chemistry). I do so, not to boast about my academic credentials but to draw attention to the fact that I am trained in the scientific method and more importantly I am trained in spotting bad science. Diet is certainly not my academic specialism but as an ultra-endurance athlete it is one that I have a great deal of interest in and one that I have studied extensively. Perhaps the most important thing I have discovered from my research on the topic is in spite of huge amounts of data that actually exist there is a huge lack of what I would describe as hard understanding on the topic and the subsequent substitution with what is otherwise known as bad science. And for those of you that prefer a bit of straight talking; that’s “Bullshit” in American English or “Bollocks” in British English by the way.

The term “Bad science” which has been popularised in Ben Goldacre’s excellent book with just that name “Bad Science”. ( It does not mean for one minute that these conclusions are actually wrong. What it means is that the conclusions have been derived on incomplete data. But before analysing what we mean by bad science, let’s look at some “good, hard science” and then make a candid comparison. Newton’s laws on motion can be described as good, hard science. Newton, about 300 years ago formulated a set of very simple equations that were able to describe the whole of the then known physical word. These laws and his equations, whilst not only being very simple were extremely powerful. They had a predictive nature about them that is fundamental to the concept of good science.

Describing what we know about diet and ultra-running performance can indeed be described as bad science. This is not at all surprising as it is a hideously complex topic and isolating parameters that can be studied in order to determine their precise effect on performance to the degree of accuracy that Newton was able to describe the effect that mass has on acceleration and on the applied force when he formulated his second law is close to near impossible. Wouldn’t it be wonderful to be able to describe a sports diet in such a way as to say that increasing your intake of x% of y ingredient will lead to a z% increase in performance; Alas it is not so. Not only does the diet effect performance but also a host of other environmental factors that over a prolonged period of time simply cannot be controlled. In studies of this nature there is a generalised absence of what would be the control group, for no other reason than nobody really knows what the control group should actually be. At best we have “best attempts” to isolate factors and study them but in spite of tremendous efforts on the part of the researchers they remain in the realm of bad science simply because of the impossible nature of isolating the parameter that is being studied or of simply establishing a valid control group, exempt from being corrupted by other factors. This doesn’t mean their findings are incorrect, only that they are flawed as a scientific endeavour. It also doesn’t mean that we haven’t discovered anything; on the contrary, there has been a major advancement in our knowledge on the topic. But wading our way through the myriad of scientific complexity is a daunting task, especially when so much research tends to be contradictory. Translating all of this science into a practical diet, that is easy to follow and that leads to a genuine optimum performance for a particular individual is near impossible, especially when we include the different genotypes of all of the athletes that may be interested in this material.

What we are left with is a philosophy, a set of general rules that certainly have a lot of valid use, but are by no means a detailed recipe for success. Many authors have tried to do just this and as would be very natural for a topic of this nature they have evoked the theory of evolution and justified diets on what our bodies had adapted over millions of years of evolution to eat. Whilst I believe that this approach can successfully lead to identifying the major trends in an optimum diet, I do not believe that it can lead to optimum performance in a race. Our ancestors generally had access to poor quality foods and developed highly efficient systems for extracting energy from these foods. By injecting high quality, energy rich foods into this system we can give it an extra boost leading to even greater performance.

So then, on to the bad science. It is unfortunate, especially after the introductory paragraphs but the nature of the topic is such that it is all we have. What I will express is of course is simply an opinion. I consider it to be a valid opinion though as it is at least coherent with what I know intellectually and what has worked well for me in running ultra-marathons. I will argue a case, based on evidence but much in the way that a lawyer would argue a case in court. I will be coherent in what I say and I will back up with as much data as I have available. However, it will remain an opinion albeit an informed one; based on my own academic research as well as my own experience in running ultramarathons. Ultimately it will be another piece of bad science, although I will argue there is a lot of truth in what I am offering.

This lack of hard data has been summarised in Mark Hine’s excellent book “Our natural diet” ( where Hines draws attention to these very problems and offers an interesting synopsis of what may well indeed be our natural diet. But is our natural diet the same as an optimised diet for ultra-endurance running. It is an interesting question.

The diet for an ultra-endurance athlete has to allow the athlete to achieve the following goals. First and foremost has to be the ability to maintain a prolonged effort over a prolonged period of time. Following that the diet has to provide enough energy for adequate training, allowing the athlete to achieve his or her goals. Coupled in has to be the aspect of good health. A sudden burst of energy for training purposed does not necessarily constitute optimum diet if we are considering our long term health.

Back to the bad science then. In the void of any hard reliable data upon which to make any hard scientific conclusions the developed world in general came to the conclusion in the 1980s ( that fat was bad. As athletes, weight is one of the most important aspects that have an effect on performance. Carrying a couple of extra kilos has a huge effect and slows you down so there is immense interest in keeping that weight off, or losing it if we carry too much of it. So when the general opinion in the field was that eating fat made you fat, we all diligently followed our low fat diets, convinced that this was the only way forwards to optimum performance. The problem is that this mind set has recently been shown to be complete nonsense. ( Noakes is in my opinion one of the very best sport’s scientist ever in the field. Not only because he has written a host of literature based on actual research but because he is willing to change his opinion and recognise that he was wrong with previous conclusions that he had made. His book “The Lore of running” is the staple reference point for any runner that is seriously considering a fuller understanding of the science behind the sport.

So then, back to the fat. Our bodies are tremendously adaptable and we are capable of adaptations in our diet that allows us to extract the necessary nutrients from our food so that we may go about our business. When we reduce or even eliminate fat in our diets, in an attempt to lose weight our bodies adapt to this regime. If the major source of calories is then carbohydrates our bodies become adapted to processing carbohydrates, and that includes converting the carbohydrate into fat to make up for the very lack of fat. The very biochemistry of our bodies changes in order to extract what is needed. And fat is needed. It is not only needed for fuel but also it plays an important role in cell protection and hence reduction in the risk for cancer. (

A host of studies analysing glycogen (Carbohydrate) stores and performance arrived at the conclusion that at least up until the marathon distance that the primary fuel for performance was glycogen. In other words stored carbohydrate and athletes went to great ends to optimise these stores. These included the low fat high carb diets as well as the famed carbo loading regimes that athletes undertook the days previous to a race. Carbo stores in the body can typically last for 2-3 hours which is just the right amount for a marathon. When the carbs run out, the athletes experience the wall effect with the subsequent dramatic decrease in work rate.

Studies on triathletes, particularly for the Iron man distance ( clearly demonstrated that the top athletes could not be burning carbohydrates as the major energy source for the duration of the event. They were winning races in about 8 hours, a supposed full 5 hours over the point when their bodies ran out of glycogen. Not only that, but at the work rates involved, whatever mechanism was producing the energy it was just as efficient as the carbohydrate burning mechanism of the marathon runners and lasted a lot, lot longer. It is this precisely this latter mechanism that we are interested in in ultra-running if we are to truly unleash our potential.

So, in the low fat, high carb diet the body is being constantly trained for precisely that combination and never really learns to burn fat. The body becomes adapted to carbs as the primary fuel source, so when the carbs run out, the body subsequently crashes. But it doesn’t crash because it has run out of fuel, it actually crashes because it doesn’t know how to burn the huge reserves of fat fuel that it still has. It is little wonder that whilst on this diet, study after study has demonstrated that it was the amount of stored glycogen that affected endurance performance and every possible trick was used to get more carbs into the body. (  Once the carbs ran out, the athlete hit the wall. The problem was though, that this still didn’t explain the top performances of the top triathletes as they were able to keep up work rates comparable to the top marathon runners but clearly they were not hitting the wall at 3 hours. They weren’t even hitting it 3 hours later. What was happening? And then came the revelation that shocked the sports science community: These athletes were not actually following a low fat diet after all and they were compensating with significant calories from fat. Not only that but the athletes actually confessed to “cheating” on their trainers prescribed diet and were eating considerable fat as well. The conclusion being of course that these athletes were fat adapted. They were not actually using carbs as their major energy supply but fats; stored body fats. Their bodies were so efficient at burning fats that they were capable of comparable work rates to the top marathoners of the day who were burning carbs. So instead of focusing on improving our ability to store glycogen we should be training our bodies to burn fats.

So the low fat diet recommended by so many sports nutritionists would not only appear to be highly mistaken for an ultra-runner but it would also appear to be a major hindrance in achieving optimum performance. By eating a low fat, high carb diet, the body becomes adapted to metabolising carbs, and more importantly it becomes very poor at metabolising fats. What we need to do is move to a high fat low carb diet in order to train our bodies to burn fat. When all we have is fat to burn, the body adapts to burning fat, and when the body is properly fat adapted it can run and run and run for a very long time. And this is precisely what we are trying to achieve in our ultra-running.

So the high fat diet has suddenly become fashionable and there is a growing trend in the sport towards it. With the same mistaken evangelism that promoted the low fat diet, we now seem to be becoming obsessed with the low carb diet. Carbs, at least to some extent have become demonised and a dietary backlash against carbs is now being observed. But going completely the other way isn’t the answer either. Those elite triathletes that were sneaking fats into their diets and doing the top times in Ironmans weren’t just only eating fats. They were eating considerable carbohydrates too. More specifically; carbohydrates were the official staple of their diets but, and it is an important but; they were eating considerable fat too. In other words, and this is where we come full circle; they were eating a balanced diet! This of course actually makes good common sense. Extremes in general are bad and often the best way is somewhere in the middle.

The “high fat - low carb” paradigm is equally misleading as the “low fat - high carb” one. Both terms are inherently mistaken and both lead to considerable imbalances for what can be considered as being optimum performance in ultra-endurance athletics. What we should be talking about is simple shifts in the percentages of these nutrients, and subtle shifts at that. Barry Spears “The zone diet” ( does just this and whilst anyone trying to follow this diet will require a degree in biochemistry to understand what he is going on about, the message can be neatly summarised as eating a bit more proteins and fats and a bit less carbs. Instead of eating 60% carbs, Spears recommends approximately 40% carbs with 30% fat and 30% protein. This can hardly be called a low carb diet as carbs still make up the greatest proportion of the macro nutrients but it is never the less an important shift from the more established traditional marathon runners diet. More to the point, the USA national swimming team that Spears coached whilst on his diet ran riot in the in 1980s and took pretty much all the medals that were worth having in the USA. Clearly he was on to something.

Training the fat metabolism.
The first stage in training our bodies to metabolise fat is clearly to increase the fat in our diet. ( This doesn’t mean eating massive amounts of fat like the famed Atkins diet but simply shifting the emphasis of the diet towards fats. Remember, we are adjusting the percentages without making major jumps. 30% of total calories from fat, on a day to day basis can be considered as a healthy “high fat” diet. ( But also an important aspect of training fat metabolism is to train when the body is depleted in carbs. This can best be achieved first thing in the morning and training before having anything to eat. Whilst the body will not be completely depleted as the glycogen reserves will not be empty, they will be significantly depleted and as all food from the previous evening will be digested it will at least force the body to access the reserves and this includes the fat reserves. It is important not to force the body too hard straight after waking up, especially as we get older and lose the elasticity in our arteries but by all accounts, a lower work rate leads to a higher percentage fat consumption, although total amount of fat burned increases with exercise intensity. ( 

Personally I train religiously every day before work for about an hour. I take a coffee to get me going and then hit the road no matter what. Consistency and the formation of the habit are absolutely crucial in provoking the fat adaptation to take place. It is a slow process and not something that happens quickly. If you chose this route to ultramarathon success you have to be prepared to forsake short term gains for the long term ones. Training for ultra-marathons is even more arduous than the races themselves.

The major component of any ultra-distance athlete’s training programme has to be the weekly long run. Out of racing season this will typically be anything between 4 to 6 hours with the occasional 10 hour run for me. On these runs you have to eat whilst you run and although I have no scientific evidence or research to back up some of the following statements, I can say that my own personal experience more than justifies what I am recommending. We are interested in burning fats, but to burn fats we also need to burn carbohydrates ( A useful analogy is that of the pilot light and the major flame in a furnace. Without the pilot light of the carb flame burning, it is impossible to ignite the major fat flame. To this end it is important to consume carbohydrate during the long runs as without them, the fat flame does not burn. But the trick and it is a difficult trick to master is to consume just enough to keep the pilot burning, thus forcing the major fat flame to keep burning. Too little carbs and the flame goes out, too much carbs and the body takes the easy way out and burns them, at the expense of the fat flame.

So just how much carbs should you eat on you long training runs? There really is only one answer to that as far as fat adaption goes and that is as little as possible. When you feel your energy beginning to dip then that is definitely NOT the moment to take the carbs. This of course flies directly in the face of traditional advice which recommends taking carbs on a regular basis precisely to avoid this dip. Only when you are starting to feel light headed and that there is a considerable loss in performance should you eat them. And they should be relatively difficult carbs to extract as well such as fruit. Personally I go for the dried fruit as it is energy dense relative to the weight you have to carry. Gels are absolute no no’s as far as training runs are concerned. You will take just enough to lift you out of the downer, and absolutely no more if you are genuinely interested in adapting your body for fat burning. I am a great fan of dried fruit and nuts. The dried fruit contains the carbs and the nuts contain lots of fat and proteins. At this point I need to point out that this is what seems to work for me. This is definitely not a statement based on a literature research.

In taking this strategy it is very easy to get it wrong. In a carbohydrate depleted environment you are essentially starving yourself. We have seen that carbs are important in the fat metabolising process and the complete absence of them in the body can be catastrophic. Indeed, the body will simply not allow a complete absence of them in the body and it has been show ( that in the absence of glucose in the blood, the body manufactures glucose by catabolising proteins. The brain mostly functions on glucose so the very survival of the organism depends on carbs being present in the system and will not allow zero point to be reached and starts to manufacture them internally. In lay terms that is tantamount to the body eating its own muscles and that is clearly counterproductive to any sports performance.

Clearly though, the purpose of all this is to promote fat adaptation and must not be confused with other aspects of training. This requires some considerable discipline and self-knowledge as this will almost certainly equate to slower times in the training runs compared to fuelling them with a carbohydrate rich foods. Indeed, on a typical 50 km training run that I often do, I will deliberately set out without eating breakfast. On a day with breakfast this will often take me 4:40 at a reasonable training pace. Without breakfast it always takes more than 5 hours, sometimes even longer. A casual observer will immediately point out that you can’t train properly without having eaten breakfast as you are clearly not working as hard and that the difference in times proves the point. However, the whole point of training whilst in a fasted state is not speed per se but is all about developing the fat adaption. Continuous races that take place over several days are not won on speed. They are won on endurance, and endurance is all about development of the fat metabolism mechanism in ultra events.

Other legitimate aims of any training session such as increasing your aerobic capacity and the development of speed clearly cannot be achieved by taking this strategy and more carbs should be consumed. Indeed, when I want to practice race pace, or develop speed I will always eat breakfast. For speed the body needs to be well fuelled. However, I would argue that the major purpose of the weekly long run for an ultra-distance athlete is to promote endurance and fat adaptation. Improvements in aerobic capacity and pace are the realm of shorter distance higher intensity workouts. The fact that the training run takes longer should not be the issue here, you are training for performance on race day and that will require shorter term sacrifices. But little by little, especially if you start to keep accurate records of your own training you will notice improvements in speed and endurance as the fat metabolism starts to become more efficient in your body.

Race day.
On race day we are all looking for a maximum performance. An ultra-marathon race for me can be easily divided into two sub categories as far as nutrition is concerned. The first are the 100 k races on tarmac or good trails. They are fast races and typically take less than 12 hours. My last 100 k clocked in at 8:49 which is not too shoddy a performance for a 51 year old. More importantly, my pace was extremely uniform and at no time during the race did I run out of energy or hit the wall. In this last race I didn’t eat breakfast. Not because it was part of the race plan but because I simply wasn’t hungry. Hunger is a good indicator to if we actually need food or not and for an ultra-run, I am not in favour of forcing the issue. I had a good fatty meal of sausages, ham and eggs the night before with just a few chips so I knew my reserves were full. I was also less worried about the absence of breakfast as I know that my fat burning metabolism is good. During the race, as soon as I noticed even a slight drop in speed I would drink an energy drink, or take a gel. The purpose of race day is to perform. Race day is when you get back what you put in and then, and only then is when you fuel your body for maximum performance and that means carbs. The train low, compete high strategy has indeed gainded popularity amongst many elite athletes. (

When you have trained properly in a carb depleted environment you have developed your fat metabolism to the full and when you finally inject considerable carbs into your body whilst running it is like igniting it with rocket fuel. The high consumption of carbs during the race not only keeps the pilot light burning brighter but also allows this very pilot light to ignite even more fats as though they were being burned in a blast furnace. What you are doing on race day by taking in high quantities of concentrated carbohydrate is actually providing an optimised environment for the burning of fats. And that leads to optimum performance. It is easy to understand the origins of the mistaken carbohydrate paradigm for optimum sports performance in ultra-distance athletics; the true function being that carbs facilitate fat burning. However, the underlying point, and it is one that cannot be stressed with sufficient force is that this only works in fat adapted athletes. During training it is a low carb diet; in a race it is high carbs still.

For any race that takes over 12 hours we require a different strategy. My own experience on relying on carbs and my internal fat store alone simply does not seem to cut it. Races over the 100k distance can take anything between 24 and 72 hours; at least for the kind of races that I like to do and the fuelling strategy returns to what could only be described as a typical balanced diet, at least in terms of the macronutrients. I will go for concentrated foods as in fibre depleted but certainly the combination of macronutrients resembles a typical food pyramid. After 12 hours I can only imagine that my fat reserves start to fail too. I clearly have much more fat to metabolise, I can see it; but after 12 hours it certainly appears that all of the readily available fat seems to have been burned and that accessing that second store of fat requires a bit more work.

The pace that the longer runs are run at is quite a bit slower than a typical 100k and that means that eating solid food is not only feasible but is actually quite pleasant as well. The intake of solid food early on in the race, and by that I mean a good combination of carbs, fats and proteins seems to keep me going for a very long time indeed.

A particular revelation in my own experience took place when I was running the Badwater ultra marathon in the States. About the half way point I switched to eating sandwiches that were soaked in olive oil and that seemed to pick me up and give me a massive boost of sustainable energy, far above the energy levels that I was experiencing by eating carbs alone. The combination of the carbs, and I strongly suspect the oil, provided a huge amount of fuel that went straight into the furnace. So, is it possible that we run out of available fat reserves too? And by replenishing these with readily digestible fats like olive oil we substitute the readily available fats in our bodies? The fat burning mechanisms in our body are already fully activated and all they need are the fats to burn. This would indeed be a great topic for a scientific study but in the absence of which I will simply try to perfect the method empirically on my own experience. Eating fats after 12 hours into the race it would certainly appear; equates to optimum endurance performance in the longer events.

Summarising then, fat is the major energy provider during an ultra-endurance event and as such athletes should be training in such a way as to promote this biochemical pathway in the body and this means training in a carb depleted state, typically fasted and before breakfast.

As a general rule, an ultra-endurance athlete should be eating a balanced healthy diet but one that is subtly shifted towards fats, with no radical exclusion of carbs. Carbs are still very important.

During a race the athlete needs to consume more carbohydrates than in training in order to reach optimum performance and the longer the race, the more important are the fats and these have to be consumed to maintain performance.

And finally, before I get slated for the “bad science” this is just a synopsis of my experience and stuff I have read. I’ll leave it up to the actual sports scientists to collect the data and verify the hypothesis.