The Future of Fat-Burning

By February 5, 2016 November 11th, 2016 Fat-Burning Journal, Nutrition

Scientific support for low-carb/nutritional ketosis rises at the inaugural Metabolic Therapeutics Conference.

My recent participation in the first-ever Metabolic Therapeutics Conference was a refreshing and hopeful look into the future of nutrition and fat-burning, but it also brought to light the many challenges ahead.

It’s now being widely accepted that the ultimate fat-burning metabolism is created by eating certain foods while avoiding others. As carbohydrates are reduced and fats increased, the metabolism kicks in to burn more stored body fat for energy, both at rest and during physical activity. Fatigue, pain, hunger and many other abnormal signs and symptoms that can reduce quality of life can suddenly disappear.

Taking it a step further, a very low-carbohydrate eating plan increases fat-burning even more, and also raises ketone production. Ketones are another source of energy, especially for the brain but also the heart and other body parts. Benefits include reduced reliance on sugar for fuel, which can reduce tumor growth, and much more.

Ketones are not only used for energy in the heart, brain and other tissues, but the state of nutritional ketosis may be the ideal approach to prevent most of the common chronic diseases from Alzheimer’s to cancer, and diabetes to heart disease. This healthy nutritional state, which medicine has used for more than 100 years to treat epilepsy, is also thought to successfully treat many types of brain injuries, including Alzheimer’s, along with obesity, Type 1 and 2 diabetes, brain tumors and other cancers.

One of my earliest experiences with ketosis was while fasting 43 years ago. We now know that fasting is not necessary to get the body to increase fat-burning significantly — you can do this simply by eating the right delicious foods.

Humans evolved eating unprocessed, low-carbohydrate, high-fat foods, and this was a key stimulus to how the human brain has evolved. High fat-burning played a key role, and ketones were part of this metabolism, a state that was the result of both foods consumed and, during times of low food availability, fasting. Add to this the most common physical activities that included long-distance walking and jogging with the occasional sprint.

Fast forward to Jan. 28-30, 2016, and the first Conference on Nutritional Ketosis and Metabolic Therapeutics in Tampa, Florida, held in conjunction with the launch of the new scientific journal by the same name. Most of the important researchers who have been publishing their work on low- and very-low carbohydrate eating, including nutritional ketosis, over the past 20 years, especially in the last five years, were presenting their work.

This conference was encouraging from the standpoint of the low-carb lifestyle and nutritional ketosis coming of age without any dramatic changes to the knowledge base formed over several decades; however, it also highlighted just how much work still needs to be done before this concept becomes accepted among the scientific community and general public.

Many of the studies presented, from the treatment of brain tumors and autism to resolving obesity and eliminating meds in diabetics, were published in mainstream medical journals. It was powerful data no one could ignore and everyone can use, if they choose. While the scientific stamp of approval has now been made, it must be noted the scientific studies showing effectiveness are new.

Unfortunately most practitioners will not suddenly recommend a ketogenic diet. Yes, small numbers of clinicians already do, but most don’t and won’t make it a standard of care any time soon. Most still think it’s crazy after all these years.

One problem is that eating healthy and natural food is not a profitable venture. The fact that it might eliminate your need for medication, make you feel — and be — younger, drastically reduce your risk for chronic disease, fix your brain, and other benefits too numerous to list here — and does all this without side-effects — makes it a difficult sell.

Backing this up, governments from around the world — including the U.S., New Zealand and Australia — frown upon it. Many health practitioners, including those who have a main focus on food, are not up-to-date on it, often confusing it with keto-acidosis (a serious condition sometimes encountered by diabetics).

Another problem is competition. Surgical procedures and medications are huge businesses that don’t like to compete. The result is too few clinical cases are treated with better eating, despite it being a safe, simple, successful and inexpensive remedy.

Furthermore, this approach is viewed as just another “diet” in the mainstream, mixed in and diluted with the many other, mostly unhealthy, diets consumers routinely choose to try, including many popular low-carb plans. Following a diet, of course, is not the same as finding the best eating plan for your particular needs, whether that puts you into a state of ketosis or just high fat-burning. You can’t go wrong.

And so, the traditional medical model is alive and well — wait until you have one or more of many medical diagnoses, then, and only then, can you treat it with a ketogenic “diet.” Why not start now with the best food plan?

Also disappointing but not a surprise were the many sponsor companies on hand promoting new keto dietary supplements and so-called super-foods. I prefer my fat-burning coffee with real food such as a whole egg, heavy cream and coconut oil, rather than processed powders in a pill or scoop.

The conference also highlighted studies of athletes who were in a very high state of fat-burning. Nothing new, but something to behold when published studies show that those in ketosis can perform better, and healthier too, with fewer “side-effects” of training, such as trauma-related inflammation, poor recovery and injuries.

My poster presentation was a case report of an Ironman athlete, which you can see here. I also was co-author of a poster presentation with Dr. Cathy Dudick, a trauma surgeon and triathlete from New Jersey. Read our abstract here.

Dr. Mark Cucuzzella also contributed by presenting ideas that would have been heresy not long ago. He teaches his West Virginia University medical students about nutrition, real food (he even teaches them to make Phil’s Bars), and how to get patients healthy and off meds. This is one small wonderful step for the future of healthcare.

Ultimately the conference reinforced what we have known for 40 years — eating in a way that promotes the body’s natural and powerful fat-burning metabolism leads to better health and human performance on all levels. And it’s usually quite simple: Eat real food, find your level of carbohydrate needs to create the healthiest brain and body right now. For athletes, including those in nutritional ketosis, burning more fat can also improve performance while building health.


  • Ryan Spearman says:

    Hi Ivan,

    I have been hflc for a couple of years and doing half marathons, training predominantly at my MAF rate.
    I have toyed with being in ketosis quite a few times and enjoyed the results, but also allow my self less stricter periods meaning I’m not in full ketosis, although I believe I am still relatively fat adapted.
    My question is- is there a definitive guide for how many ketones are in the blood stream on the ketosis spectrum? Is there a number when you’re definitely in, or one when you are simply burning more fat than the average?
    I’d like to buy a ketosis meter and really understand how my diet affects the fat burning properties of my body


    • Hi Ryan –

      There is no definitive guide.

      Ketosis and “fat-burning” shouldn’t be treated analogously. Ketosis is best understood as the body’s “fifth gear” while fat-burning is the body’s “4th gear.” In other words, where fat-burning matters the most to ketosis is that you have to go through fat-burning to get to ketosis. To cite just one difference, you can be in ketosis but burning a much lower volume of fat than usual, simply because you are at rest. Similarly, fat adaptation has little to do with how much fat you are burning at any given time, but rather by how easily and readily you can go from sugar-burning (when you are working out anaerobically) to fat-burning (when you are working out anaerobically). Many phenomenally fat-adapted athletes rarely if ever go into highly ketogenic states.

  • fiona catto says:

    Hi there, I am wondering if you can give me some advice. A couple of times, I have neared the end of the two week period of going high fat, high protein. However, both times I encountered leg cramps about one week in. Each time, it’s deterred me from continuing. Can you tell me why I might be getting cramps? is it perhaps that my body is self-regulating and trying to become accustomed to the ketogenic diet? I guess I’m wondeting if i need push past them and with time my body will adjust, or not?!

    • Hello, Fiona,

      Yes, it takes some getting used to. If the cramps are due to exercise, take it as an indication that you need to exercise at a lower intensity (and usually also for a shorter period of time) throughout the adaptation period.

      There’s really a lot of changes that happen when you go low-carb. Let me give you an example: carbs are stored using a lot of water, which means that when you burn them, a lot of water is released into the bloodstream for use by the body. But when you start to burn more fats (which aren’t stored using water) the body suddenly stops having this additional water supply that it used to count on. So burning fats is not just a matter of getting better at burning fat, but also changing parameters of water utilization (and many other different changes up and down the body).

      It takes getting used to all of them, and it’s better to reduce the demand on your body until you do.

  • Wolfgang says:

    Hello from Austria,
    I am an ultrarunner, I incorporated MAF training already back in 2009. I am 45 years old which leaves me with a MAF heartrate of 140. ( 180 – 45 + 5 )
    I switched to a ketogenic diet 2 months ago, while I am feeling much better overall I did not progress with my MAF times. Generally I got the feeling I could add a few heartbeats since I must burn predominantely fat on a ketogenic diet, does that make sense or should I better stay with my original number?
    Many thanks!
    Best wishes

  • Mel says:

    PS (Mel again):
    the oatmeal I used to eat is kind of raw oat-flakes with no additionals.
    I combined it yoghurt with banana, nuts, rasins, and honey. Then I just added a bit of cold water (no cooking) and ate it straight away.
    Lots of sugars, so maybe add the oat-flakes to my more vegetable and fat based breakfast to keep the metabolism going and prevent cramp during running?

  • Mel says:

    Thanks Ivan.
    I run (ultra) marathons and cross train regularly. I’ve been eating high fat low carbs for a long time, and last year I had my VO2max measured and it was at elite level.
    Since a few months I follow Phil’s advice to skip oatmeal and bananas as well, and I only train on my MAF HR rate.
    Now I still eat little or nothing before a run but I eat things like eggs, avocado, vegetables, fish, meat (prepared in coconut oil), nuts, tahin for breakfast, lunch and dinner and sometimes apples, grapefruit, French/Greek cow/sheep cheese and Greek- or sheep yoghurt.
    I drink water (with lemon in the morning), herbal tea and coffee (sometimes with coconut oil).
    But since then I experience lots of cramp and stomach issues during running.

    I never had those issues before, when I did my morning runs mostly on an empty stomach but ate yoghurt with banana, nuts, rasins, oatmeal and honey after the training. During the rest of the day I ate then similar like described above, but less fat and more grapefruit and yoghurt.

    During races this new stomach discomfort costs me a lot of time since I have to visit the bathroom regularly.
    How to run painless again while eating and training healthy?

  • Mel says:

    You say “We now know that fasting is not necessary to get the body to increase fat-burning significantly — you can do this simply by eating the right delicious foods.”

    Could fasting be good if you want to detox your body after some less healthy days/weeks, even if you’re already a fat burner?
    Or would you say that eating the right foods is better than fasting?

  • Nicole says:

    Hi Ivan, I’v been doing MAF training for 5 months and it’s going well albeit slowly. I train at MAF around 7 hours per week. I also did the 2 week test early on and since then I’ve cut back drastically on the carbs and try and eat more fat and protein. Before changing to the LCHF diet lifestyle, my weight fluctuated around normal to slightly underweight. Now however I am definitely underweight and just cannot put any weight on. I know you might say it is a question of calories but I just don’t feel like eating much more. I try and eat a lot of cheese, almonds, walnuts, (not Phil’s coffee as that is too rich for me), fatty meat. What can I eat that will help me gain back some weight? Should I take in more carbs?

    • Nicole:

      How do you know that you are underweight? Do you have low energy, low blood pressure? is your digestion OK? Are you experiencing symptoms of depression?

      • Nicole says:

        Hi Ivan, blood pressure and everything else OK (had recent blood tests too) but I am below the norms when you look at weight charts. What I have noticed is that this week we have had house guests and so LCHF diet has gone out the window and I’ve been eating more carbs than usual. I have done a few runs too over this past week and I found that my MAF pace increased significantly. So now I am thinking that I need to eat more carbs. It kind of makes me nervous as I am worried that maybe my fat burning ability will suffer. How do i know if I am fat burning without doing a lab test?

        • The best way to know you’re fat burning is that you don’t get very many mood swings, don’t get tired, and seem to have energy even after very long runs.

          Whenever someone’s performance dramatically increases when they eat carbs is because their fat-burning systems haven’t developed. So while it’s likely that a high percentage of your energy is being provided by fats (when you’re LCHF), this also means that you aren’t fueling the powerful (sugar-burning engine). This means that overall, you aren’t producing that much energy.

          Essentially, when the body is healthy and fit, you should see your submax speed sustain itself easily. For example, my MAF pace at 20 miles is about 8:10 min/mi, whereas my MAF pace at 5 miles is 7:50 min/mi. Since my body is fueling itself primarily with fats, it doesn’t really run out of fuel.

          To answer your question specifically, even if your fat-burning were low, eating more carbs could not solve that problem. And the best way to know whether you’re burning fats is (1) if your MAF test continues to get faster, and (2) if the speed differential between your first and last mile continues to drop with time. Otherwise, you can get RER (respiratory exchange ratio) tests done at rest and various speeds.

  • Vance McNulty says:

    Having done both ketogenic and ultra high carb diets I can say, for myself, that higher carb is far better. I remember getting terrible cramps on the ketogenic diet with massive carb cravings that rarely went away. My wife and I both used the diets and she enjoyed the ketogenic diet quite a bit and never had the problems I did. My best advice is you must spend at least 12 weeks following the ketogenic diet with NO CHEATING. You’ll learn A TON in those 12 weeks about your body and whether you have the physiology to follow it successfully.

    • Vance:

      You may have hidden issues that may make it difficult for you to follow a ketogenic diet. What I mean by this is that the ketogenic diet works well with a certain kind of physiology: a human physiology. Because of how carbohydrates work in the body, your physiology would have to be different on a fundamental level for a high carb diet to be truly healthy (read:healthier than following a low-carb diet) for you. That kind of fundamental difference is unlikely enough that I’d expect you should already the subject of several groundbreaking case studies, if a high-carb diet is “far better” for you in the sense of “making you healthier.” A much more likely scenario is that there is some hidden factor that is causing a negative physiological response (read: cramping).

      Negative responses don’t mean that a low-carb diet is bad for you—for example, when coming off alcohol addiction (alcohol is metabolized in a semi-similar fashion to carbs) people can also get a series of potentially damaging side-effects during the detox period. This, of course, does NOT mean that some people have a physiology that “just tolerates” alcohol: their physiology would have to be fundamentally different to the physiology of just about every other person (but strikingly similar to the high-carb healthy physiology) for that to be the case.

  • Jerry S says:

    Does anyone know when the next conference will be and where?

  • Matt K says:

    I’m particularly worried about adopting a low-carb, high-fat diet because according to some notable doctors like Caldwell Esselstyn and Michael Gregor, fats (especially from oils) and animal protein are harmful to one’s cardiovascular system and can contribute to heart disease. In addition, I’ve read about insulin sensitivity being impaired by fat consumption.

  • Chrissi says:

    I successfully achieved ketosis for over a year while I was training for an Ironman. I did enjoy the results.

    Now that I am post IM my interests have shifted slightly. I am interested in putting on some muscle. Insulin is anabolic. If you maintain constant low levels of insulin via ketosis, then how can muscle be gained?

    • Chrissi:

      To a large degree, you won’t be able to. Simply stated, while I believe that it’s quite important to be able to reliably achieve ketogenic states for health and endurance purposes, I don’t believe it’s necessary to perpetually exist in one, for either health or endurance performance. What I do in order to train more hybrid athletic abilities is to emphasize the relevant fuel macronutrient (fats for low-intensity and low-glycemic carbs for high intensity) the two meals prior to the workout (meaning over the prior 18-24 hours).

  • Geoff says:

    In Phil’s eg above the triathlete increased the fat portion of there diet to 70% (or there abouts), can you give some meal tips, foods that you would consider ‘fat’ or even better could you give some meal plans for 7 days that show the afore mentioned ratio of fat/carbs/protein. Thanks

  • César says:

    Wow, ¿De dónde sacas tiempo para responder tantas preguntas y tan bien explicado?
    Quiero tu método.

    • César:

      Yo soy el encargado de contestar preguntas para el Dr. Maffetone. Soy su editor de investigación y también soy uno de los entrenadores fundadores de MAF. ¿Qué preguntas tienes acerca del método? Si quieres te puedo apuntar a algunas fuentes principales de información acerca del método MAF. ¿Preferirías artículos o libros?

      • César says:

        Gracias, Mi comentario anterior era de mucha admiración hacia usted.
        Me gustaría saber como continuar entrenando después de las Dos Semanas, para seguir usando la grasa como combustible aunque ya haya empezado a agregar otros alimentos, uno por día, como las legumbres y las frutas.
        ¿Sigo con 180-edad?
        El 20 de Marzo tengo una carrera por montaña, ¿qué pasa si supero mis ppm solo por ese día?
        ¿Qué proporción de nuevos alimentos incorporo? ¿20% de carbohidratos? ¿voy a seguir quemando grasa?
        Muchas gracias desde Argentina.
        Thank you, my previous comment was a lot of admiration for you.
        I would like to know how to continue training after two weeks to continue to use fat as fuel but has already started adding other foods, one per day, such as legumes and fruits.
        I continue running a 180-age?
        March 20 I have a running trail, what happens if I exceed my bpm only for that day?
        What proportion of new foods incorporate? 20% carbohydrates? I’ll keep burning fat?
        Thank you very much from Argentina.

        • César:

          Siga con 180-edad (ajustando conforme a su salud, como dicen las instrucciones).

          El ritmo cardiaco MAF es un ritmo cardiaco de entrenamiento, que no necesariamente aplica a las carreras. Lo mejor es encontrar un ritmo al que usted puede correr una carrera rápida pero sustentable. Muchas veces, este ritmo es mayor a MAF.

          Después de las 2 semanas, lo mejor es ir lentamente incorporando carbohidratos, escuchando al cuerpo para ver si vuelven los síntomas de intolerancia a los carbohidratos. Siempre y cuando no vuelvan los síntomas, usted continúa comiendo una cantidad saludable de carbohidratos. Seguirá quemando grasa, particularmente si continúa entrenando bastante al ritmo cardiaco MAF.

  • Santi Soliveres says:

    What are the best foods in terms of fat for an athlete. I know avocados are pretty good, but would like to know some more to include them in my daily meals.

    You do a great job!! Thanks!!

    • Santi:

      You’re welcome. I’d say that the very very best fat is coconut and its assorted products (cream, milk, oil, flour). Coconut oil is excellent to cook with. Other good veggie fats are tree nuts, particularly macadamia nuts, almonds. etc. If you eat meat, organic free-range steak also has a large amount of fats, for example.

  • andy says:

    Hello Phil and Ivan,
    thanks for all the great info in your blog.
    The case study of the female Ironman athlete is very interesting.

    Maybe you could explain a little bit more in detail why you think it is so important to maximize the ability to use fat as energy source for endurance events.
    Lets evaluate the following scenario:

    If we take a typical male age group athlete (70 kg, 180 cm) who manages to average an energy expenditure of about 800 kcal/h during an Ironman event that would bring him to the finish line in approximately 9,5 hours (1:00 swim – 5:00 flat bike course – 3:30 Marathon).
    That gives an overall demand of 800 *9,5= 7.600 kcal. Approx. 2.000 kcal of carbs are stored in the muscles etc..
    That leaves 7.600 – 2.000 = 5.600 kcal. If we assume that these 5.600 kcal will be produced from 50% fat and 50% carbohydrate the athlete would need 5.600/2=2.800 kcal external carbs in 9,5 hours which is equivalent to 2.800/8,5=330 kcal/h. (I divided by 8,5 as the athlete will not consume any carbs during the swim).
    The 330 kcal/h can be consumed by bars, gels and iso drinks provided at aid stations on course. If you train your digestions accordingly and the effort in relation to the VO2max is not too high I think 330 kcal/h is not an unrealistic goal and can be handled.

    What is the advantage for this athlete if he could produce not only 50 % of the energy by fat but e.g. 80 %?
    Do you think the athlete could in this case go faster?
    What would be the theoretical final limiter for an age group athlete with a moderate VO2max?

    Thanks for reading – would be great to hear your opinion

    • Andy:

      Your example is great. Indeed, 330 kcal/h sounds like a pretty good goal.

      I agree that an athlete who could produce 80% of energy from fat rather than 50 at that same speed would have several advantages. Let’s look at the body from a design perspective. Type II muscle fibers, which primarily burn sugar, are quickly fatiguing. This means 2 things: (1) they quickly run out of fuel, and (2) the machinery that burns that fuel wears down quickly.

      Type I muscle fibers, which primarily burn fats, are built to run nigh-indefinitely. So you start to see a symmetry: the muscle fibers that burn the quickly-depleting fuel break down quickly, and the muscle fibers that burn the slowly-depleting fuel break down slowly. (There is evidence supporting the notion that DOMS—muscle soreness—and muscle wear and tear occurs in much greater measure in Type II muscle fibers than in Type I muscle fibers). To use a car example, the more sugar you consume during an endurance race, the more it looks like you’re fueling a roadtrip with nitrous oxide: you’re essentially using a high-intensity, short-duration mechanism for low-intensity, long-duration. You’re going to break it.

      That said, 50% fats, 50% sugars is quite reasonable. It’s not nearly as good as 80-20, but you’re doing better than just about everyone who runs a marathon.

      But there’s a few complexities that I would like to add. This goes to your mention of VO2 Max.

      1) There is evidence that the upper limit of an athlete’s VO2 Max is decided (for the most part) by the ratio of aerobic:anaerobic muscle fibers. The greater the ratio, the higher the VO2 Max.

      2) For an athlete with a huge VO2 Max, Fat max (the maximum rate of fat-burning) occurs at a higher percentage of VO2 max. (This is because of the change in muscle fiber ratio. If there had been no change in ratio, and only a greater ability to burn fats with the same amount of muscle fibers, we would expect the athlete to have a higher VO2 Max and a higher fat-burning ability, but Fat max would still correspond to the same percentage of VO2 Max.)

      3) In the comments, someone challenged me on a statement I made, citing (I believe) Zach Bitter’s biometrics (who has a huge VO2 max). The point they were making is that for Bitter, Fat Max occurs at a very low RQ/RER, meaning that while you and I hit Fat Max when we’re burning 50% fats, 50% carbs (say), Bitter hits Fat max when he is burning something like 87% fats. This is derived from the insane ratio of muscle fibers that produces his huge VO2 Max. We’d expect that other aerobic monsters like Mark Allen, Krissy Moehl, Kilian Jornet, Scott Jurek are in a very similar situation.

      4) To recap my points: If you change the ratio of muscle fibers, you change the ratio of fat to sugar burning at which you hit Fat Max, and you increase VO2 Max. (This is also why you find greater VO2 Max the further into the endurance fields you go).

      All this discussion brings us to a rather philosophical point, that is painful to consider. While just about every human (particularly every well-conditioned human) is good for some 4 hours of moderate-intensity endurance exercise, far fewer people are built for 8 or 24 hours of moderate-intensity endurance. Don’t get me wrong: it doesn’t mean most people aren’t capable of it, particularly when pushed. But the wear and tear that 24 hours of endurance activity represents on the body of someone with a VO2 max of 50 dwarfs the wear and tear that someone with a VO2 max of 80 experiences. The primary reason isn’t because they are “fitter,” but because one is disproportionately equipped with long-duration machinery, and both are running a long-duration event.

      It’s very hard to say what the theoretical final limiter for someone with a moderate VO2 max is. For example, we know that any stressor makes you burn more sugars and less fats at the same heart rate (because stress hormones up sugar metabolism, which clamps down on fat metabolism). So, if you give someone with a moderate VO2 max every advantage, you might put their Fat Max off the charts. Who knows.

      Hope this helps.

      • Iacob Gheorghita says:

        Even you change the fiber type, you still have a problemm. When the energy expediture exceed 3 kcal/min, the body will swich from fat to glucose. The fat burning issue works only up to one third of the maximum effort a person is able to perform.

        • The switch from fat to glucose is actually not a switch. As you go from rest to activity, energy use increases and percentage of fat-burning starts to drop. But this still means that peak fat-burning occurs for most individuals at 40-50% of maximum energy expenditure, and for extremely fit endurance athletes at 75-85% maximum energy expenditure. In essence, you may see individuals burning 15 fat calories per minute in the leading packs of ultramarathons.

          • Grant says:

            This study might help demonstrate how much fat can actually be oxidised during exercise and at what intensity:

            You will note that the low carb / high fat / ketogenic group was burning 1.54g/min on average during peak fat oxidation and this was occurring on average at 70.3% of their VO2 Max.

            So yes as Ivan pointed it is very possible to burn that level of fat calories per minute as the the average of the 10 low carb / high fat / ketogenic ultrarunners in this study reached levels of 13.6 fat calories per minute.

            Compare this to the high carb group where it was noted that peak fat oxidation was on average only 0.67g/min and this was occurring on average at 54.9% of their VO2 Max.

          • Cheers, Grant. Thanks for the source!

          • Iacob Gheorghita says:

            You are perfect right, it is not a swich, it is a shut down of fat burning.
            What somebody might be confused is that, no matter what you will do, it is not the muscle who will use more fat for energy. The muscle will continue to use an equivalent of glucose which are ketones.
            It is important to notice that the organ which will provide the fuel is the liver. The liver will enter a high metabolic state. Therefore, it will be more exposed to any toxic agression, for instance 1 g of acetaminophen when you got a flue.
            Personally, I had to use low glicemic index / ketosis diet both to increase my sport performance and to decrease the body fat.
            Such a diet is perfect but the things must be set in wright perspective.

      • andy says:

        Thanks for the quick answer which is again full of very interesting points.

        I assume you cannot arbitrarily change the ration of muscle fibers and therefore improvements of VO2max are also limited. But I understand the advantages of having many slowtwitch fibers. Especially the wear and tear and the related DOMS you mentioned seem to be a limiter for many athletes. Maybe this is the same effect that is also called “muscular endurance”?
        You see it all the time at the awards parties: Obviously the wear and tear also of pro athletes finishing on the podium is very different. Some can hardly walk and others jump around as if nothing has happened at all.


        • Andy:

          Essentially, what crossfitters refer to as “muscular endurance” is transitioning from using more Type II fibers to more Type I fibers at a certain power or intensity. Where DOMS plays a role here is that it really only happens in a big way to Type II Fibers. So, the more Type I fibers you can use, the less wear-and-tear you’ll have, and the more muscular endurance you’ll possess.

          Because of this, the freshest athletes at the end of a race will generally be the ones with the longer careers.

    • Iacob Gheorghita says:

      “The nodular adrenal gland. One or more adrenal cortical nodules can be encountered in patients without clinical or laboratory evidence of hypercotisolism (1) (fig. 19-1). The incidence of cortical nodules increases with age and is associated with hypertension and diabetes melitus. (2-4).” … “Some nodules have been shown to take up a radionuclide precursor in steroid biosynthesis and are hence nonhyperfunctional rather than nonfunctional. (7)”

      Ernest E. Lack, Jaqueline Wieneke, 2013, Chapter 19. Tumors of the adrenal gland in Dr. Christopher Fletcher’s Diagnostic Histopathology of Tumors, 4th Edition, p 1294

      Steroids are more prone to insulin resistance than the sympathetic – parasympathetic system.

  • Iacob Gheorghita says:

    From a phisiologic point of view ketosis means there is a glucose scarcity. If I am right, this means the brain will signalling the adrenal to help gluconeogenesis, meaning more cortisol which is equal nutritional stress. I am wrong?

    • Iacob:

      The body doesn’t use the adrenal (sympathetic) pathways to help gluconeogenesis. Using that pathway would increase insulin and reduce glucagon, which would reduce gluconeogenesis.

      • Iacob Gheorghita says:

        According to the Guiton’s 11th edition, page 838, regulation of gluconeogenesis, the regulation is done mainly due to direct effect of hipoglycemia but in addition, the hormone cortisol is especially important in this regulation.
        Cortisol is produced by direct stimulation af the adrenal (adrenal cortex) by the hypophysis.
        This is the reason why after quitting a cetonic regimen, individuals became obese, even faster and even more severe than before.
        What is untold regarding insuline intolerance is that slight increase in cortisol levels as a consequence of chronic stress, is the reason for.

        • I see, you are referring to fasted states. Chronic elevated levels of cortisol are indeed damaging (they lead to muscle wasting). However, it’s misleading to characterize a state of ketosis as “nutritional stress,” particularly when done correctly. For example, cortisol is also highly implicated in waking from sleep. This does not mean that being awake is “a stressful state.”

          (In particular, elevated cortisol is necessary but not sufficient to be damaging in the ways you refer. Testosterone must also be suppressed.) This comes about when the levels of chronic stress cross a critical threshold and you create an imbalance between the Sympathetic and Parasympathetic nervous systems. As long as these two systems remain at play and in balance, cortisol has not exceeded this threshold. It is perfectly possible (but not always the case) that a state of ketosis co-exists with this sympathetic-parasympathetic balance (and often does in experienced, healthy endurance athletes).

          Can you send me the case study you are referring to?

  • ROSS says:

    Here in the UK the BBC radio4 did some stuff on MAF and fat burning. the presenter was doing the 2 week test.

  • Mars Ward says:

    Great article written in a way that anyone can understand. Well done.
    Thank you.

  • ketorunner says:

    Phil, thanks for the post.

    My personal experience with a low carb/nutrional ketosis way of eating has been just amazing. And the reason I think this has worked for me is simple. It is not a diet. It is real food, and it’s the way we were meant to eat. It just went horribly wrong about a hundred years ago.

    I started this adventure back in April of 2015. I was researching to see if there was a way of not “hitting the wall” when running the marathon. I found so much information that I read and watched lectures for several weeks. I couldn’t believe that all I had been taught about running and diet was now up in the air. So I finally decided to give it a shot.

    Giving up grains and sugar was more difficult than I expected and I experienced about a week of what I can only describe as withdrawal symptoms. I am a decent runner, but I never ran so slow in my life. Plus, I couldn’t go more than a mile without hurting and feeling tired. As I had read, I expected this to happen. Slowly, I began to run farther and faster. To make a long story short, I decided I was going to do a marathon in October of 2015. I would be 59 years old. I did my first marathon in New York in 1992. I was 36 years old. My time was 3:42. I did the Baltimore marathon last October. My time was 3:34. I did not “hit the wall”. No gels, no sports drinks. My meal the night before the race was a rib eye steak and asparagus and a glass of red wine.

    I would like to finish by saying thank you to all of the people that spent so much of their time making this information available to everyone. I have never felt better. Everything has changed…for the better.


  • Rich Cook says:

    A very interesting article that I’ll be sharing with my Mom, who is challenged with my Dad’s diet needs, as well as mine (I join them for dinner most evenings). He’s gluten intolerant, high cholesterol, just had his gall bladder removed. I’m T2 diabetic (never over weight until after diagnosis) with blood glucose running high these days despite meds & walking 3-5 mi most days. The ketogenic diet looks similar to how I eat (although I’m eating too many carbs still so more change required). In any case I’ll have to read more on what you’ve said and the ketogenic diet.

    Can you point me to where any of the papers presented at the conference are posted? I’d be especially interested in reading your report.

    Any other resources you recommend?


  • Frank says:

    I can run as much as I like. I’m just starting to burn fat and my endurance has improved drastically. Will keep you posted, but I’m really convinced.

  • Frank says:

    I am an ex-sprinter who ran 13″48 on 110 meter hurdles in 1996. I has to stop my career in 1999 due to a fracture in my foot (talus). The fracture healed but the bone parts didn’t grow together well. Since then running is not easy for me since my foot inflames when I run too much. Since a few years I started trailrunning and it hurts less because it’s on a soft surface. But it remains borderline.

    Since 1 month I dropped the carbs and to my surprise, the pain is gone. I c

  • Grant says:

    Interesting case study. Did this macronutrient breakdown result in constant nutritional ketosis as this represents around 84 grams of carbs (2700kcal / 12%) usually too much to remain above 0.5mmol/l. Or was this quite cyclic? Were the carbs strategically implemented pre / post long workouts as to not throw her out of nutritional ketosis. Would be interested in how you managed timing of carbs.

    “Humans evolved eating unprocessed, low-carbohydrate, high-fat foods, and this was a key stimulus to how the human brain has evolved. High fat-burning played a key role, and ketones were part of this metabolism, a state that was the result of both foods consumed and, during times of low food availability, fasting.”

    Would this suggest that cyclic ketosis is more of the natural human state. That is I still struggle mentally removing unprocessed, natural foods such as pumpkin, banana, stone fruits and perhaps more modern items such as oats and rice which would take you out of ketosis quite easily when these were consumed. Would fruits of been less likely to be found / grown than nuts for a past ancestor? Would root vegetables / legumes have been rare and green vegetables (zucchini, spinach, asparagus etc) been abundant. It is so easy to overshoot the general 50grams of carbs to remain in nutritional ketosis just easting unprocessed, natural, real foods.

    Also when 2700kcal is required for a day, 12% carb, 13% protein, 75% fat. At what point must somebody actually ingest the 75% fat as dietary fat opposed to using stored body fat to contribute towards the fat kcal requirement. Maintenance vs weight loss. For example without doing a DEXA scan I am unable to determine % body fat, but believe I still have more to burn, and would like to decrease fat to increase power to weight ratio. How much of that 75% fat requirement can you leave to body fat stores, any thoughts here.


    • Grant says:

      I guess what I am trying to understand better is this. Your brain requires around 150 grams of carbs to feed the brain with glucose per day. So if you are not in ketosis then ketones are not kicking in towards this energy requirement hence you need carbs to meet this energy requirement. If you are sitting around 80-120g of carbs per day you are sitting in the grey area. As Jeff Volek and Steve Phinney put it ‘your brains fuel supply becomes pretty tenuous’.

      So what happens here when you eat 84g carbs? Is it a case of the body becoming fat adapted that it can quite happily break down glycerol and protein into glucose more efficiently via glucogenesis and meets the shortfall this way, or is it that the consumption of these carbs was strategically eaten around workouts to not throw the athlete out of ketosis. Or was the carbs coming from Superstarch?

      I know from my own experience I can perform well and feel great off 100-120grams carbs per day (still low carb) but likely above the threshold that I am making ketones for fuel. Hence it would appear I have a glucose shortfall for my brain that day…

      What is happening here?


      • Grant:

        I agree with Volek and Phinney (two friends of Dr. Maffetone, by the way). But the body doesn’t switch gears from ketosis and back in the sense that a car does. Furthermore, it’s a very complex system. Since the brain is at the reins, it’s not going to just sit there and maybe get enough glucose and maybe not get enough. It’ll either increase ketosis and liver gluconeogenesis or it’ll reduce muscle metabolism (or alternately, increase fat-burning through leptin) and open up glucose availability for itself. In other words, there are many avenues it can use to find fuel for itself.

        In this vein, there’s no “off and on” switch for ketosis. If you eat a few carbs, your body might decide to reduce ketosis and reduce activity levels in order to keep the brain out of the red. But if you increase activity levels even slightly, the body will allot some of those carbs as fuel, increasing the need for fat-burning and starting a domino effect that concludes in ketosis. You don’t have to be in a “primarily ketogenic state” to be burning ketones. Just like at any given time you can have a small amount of anaerobic function and still be burning fats, it’s quite possible for your body to be fueling your body with sugar, fat, and ketones at any given time because it knows it needs to.

        Look at it from this perspective: evolutionarily, the human animal’s only strategy for eating is “eat whenever you find food or run it down.” That animal’s brain has to have a very complex and extensive set of tools at its disposal to maintain its energy. The body isn’t a muscle car that for which you actively have to manage the carburetor and air filter. It’s a 5th generation fighter jet with highly redundant avionics. If the brain feels like it has to, it’ll force the body to stop all athletic activity in order to ensure its survival.

        So, the glucose “shortfall” is likely made up by a strategic reduction in total movements that day: how less likely were you to get up from your desk to the copy machine that day? How many chores that you could have done were left for the next day? My point is that your brain is actively managing all of these activities in relation to its energy needs. My point is that also, you don’t have to answer these questions for your brain. The abovementioned, exceedingly complex avionics built into your brain were built into it explicitly so that it can manage them itself and you don’t have to.

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