Updated: Mar 19
We take a look at what it means to follow a ketogenic diet. What is it, how would you go about it and can you expect performance or health benefits? If you haven’t yet read our article Fasted Training or ‘Training Low’ you might want to do so, either before or after reading this. In the Fasted Training article we discussed the differences between high and low carbohydrate diets and the timing of carbohydrate ingestion from the perspective of maximising physical performance. We concluded that in order to get the most from one’s physiology, it’s necessary to embrace a concept called ‘metabolic flexibility’ – essentially training the body to burn both fat and carbohydrate more effectively. The focus of this article is different, because it discusses a unique dietary practice whereby carbohydrate intake is kept to an absolute minimum on an ongoing basis and the calories consumed are derived almost entirely from fat and protein sources. This leads to a pronounced adaptation to the way that the human body utilises energy and is called a ‘Ketogenic Diet.’ In this article we’re going to examine this diet, how it came into circulation and whether there are any performance and health benefits.
What is a Ketogenic Diet (KD)? According to Ma & Suzuki (2018), a KD is a nutritional intervention which consists of a high fat, moderate protein, but critically low carbohydrate consumption. Carbohydrate consumption from a KD is typically accepted at 5% of the total calorie intake. Putting this into perspective, a daily diet consisting of 2000kcals, would see only 100kcals coming from carbohydrate sources, equivalent to 25g per day.
The purpose of a KD is to utilise evolutionary adaptation abilities so that the body becomes less reliant on fuel sources from carbohydrate and becomes almost solely reliant on fuel sources from fats. In principle, this adaptation could prove quite useful, because the human body has a vast supply of fat for energy, whereas it can only store around 2,000 carbohydrate calories. This means that athletes who depend on carbohydrate for energy will need to fuel regularly with carbohydrate sources in order to maintain their performance. Let’s face it, it’s for this reason that TORQ has a business, if there wasn’t a need for energy drinks, gels, bars and chews, we simply wouldn’t need to exist. The KD seeks to remove the need for traditional fuelling and instead builds a case for changing the way the body metabolises its fuel sources.
By limiting intake of carbohydrate to such a significant extent, a KD encourages fats to be converted via the liver into compounds called ketone bodies – a process that under normal circumstances would only take place during periods of starvation to ensure human survival. Once these ketones bodies are produced, they enter a different molecular pathway and are used to produce energy. According to Pinckaers et al (2017), to successfully induce nutritional ketosis, a diet critically low is carbohydrate would need to be adhered to for around 4 days. These researchers also suggest that although the focus of fat-based fuelling strategies has been to enhance the capacity of better utilising fat as a fuel during exercise, extreme carbohydrate restriction also increases the production of ketone bodies, which may provide an additional energy substrate for both the brain and the working muscles. So, there are essentially 2 benefits to a KD, utilisation of fat as a fuel is enhanced and ketone bodies are produced to provide a secondary fuel source.
How did a KD materialise? Again Ma & Suzuki (2018) explain that a KD was born from a clinical setting to support patients diagnosed with obesity related problems, pain and inflammation relief and in some serious cases, a KD diet was advised alongside patients suffering from specific cancers. However, in more recent years a KD has been implemented within a sport nutritional context with an effort to try to enhance endurance performance within trained individuals as a means to prevent exercise exhaustion from depleted carbohydrate (glycogen) stores.
From a clinical perspective, the research into the role a KD might play is interesting. Palmblad and colleagues (1991) suggest that fasting or restricting carbohydrate can reduce inflammation, not the kind of inflammation one would get from an injury as such, but more so at a cellular level. After exercising, the body experiences inflammation, as it does when it’s attached by a viral infection or other disease. A KD appears to host a less inflammatory internal environment, so could be useful in specific circumstances. In a similar vein, Gasior et al (2006) made similar assertions and suggested that a KD could be beneficial especially for children suffering with epilepsy and Henderson (2001) proposed that a KD could enhance memory and perhaps slow down or have a modifying effect in patients suffering from Alzheimer’s disease.
There is also of course a logical application of a KD for people with Type 1 diabetes where controlling and maintaining lower blood glucose levels has a distinct advantage. If you have diabetes and would like to explore the pros and cons of a KD further, please speak to your doctor. Further information is also available here at diabetes.co.uk. At the same time however, there is research to suggest that a KD could in fact be a causal factor in Type 2 diabetes. One of the researchers from the Grandle et al (2018) study said: ‘Although ketogenic diets are known to be healthy, our findings indicate that there may be an increased risk of insulin resistance with this type of diet that may lead to type 2 diabetes.’ A summary of the findings can be found here at healthline.com. The original study is available here. In the interests of a balanced discussion however, it’s impossible to ignore the role that excessive carbohydrate intake plays in the development of Type 2 diabetes. There is substantial evidence (just one example being a study in 2010 by Sluijs and colleagues) supporting the notion that a sedentary lifestyle, coupled with over consumption of calories in general can put the body into the position where carbohydrate becomes actually becomes toxic. The key words here though are ‘excessive consumption’ and as we’ll discuss a little further on, it’s not the % of carbohydrate in the diet, it’s the amount (called gycaemic load), coupled with your overall energy output and physical fitness level. We would put the case across that both a KD and over consumption of carbohydrate are both distortions of what would typically be called a healthy balanced diet.
What types of foods are generally consumed within a ketogenic diet? According to Urbain et al (2017), a typical ketogenic diet pyramid chart would consist of 75% of the daily calories gained from fats, 20% derived from protein and a microscopic 5% gained from carbohydrate.
Achieving this high fat low carbohydrate target certainly isn’t for the faint hearted and would require some serious focus. Although some would question whether this diet could be healthy at all, there are certainly healthier ways to pursue a KD than others. For example, when choosing sources of fat, an individual may wish to opt for foods such as avocado, nuts, eggs, oily fish such as salmon, coconut, and 85%+ dark chocolate rather than consuming an excess of red or processed meat, fried chicken and battered fish from the local chippy. A KD should still aim to source quality nutrients from the food choices available and even as far back as 1966, researchers Green & Tzagoloff distilled the benefits of consuming fats rich in Omega 3 and 6 and the fat-soluble vitamins A, D, E and K.
At 20% of daily calories, the protein demands of a KD don’t differ too much from that of a typical athlete’s high carbohydrate diet. Protein plays an important role within human biological regulation as it is responsible for the development and maintenance of lean muscle mass, cellular development and enzymatic control and regulation (enzymes are biological catalysts that speed up chemical reactions within the body). However, complete proteins are made up of individual components called amino acids, some of which the human body can produce itself (non-essential amino acids) and ones which it can’t produce (essential amino acids). To ensure that we ingest enough of the essential amino acids, we must hunt for protein sources which contain them. If you’re a meat eater or even a vegetarian this is not too challenging a task, because meat, fish and dairy all contain the essential amino acids. If you’re following a plant-based diet it’s more complex, because in the most part you will need to mix pulses and grains to get the amino acids you need – and try doing that on a KD where you’re not allowed carbohydrate! We’ll cover this in more detail a little further on, because although it is possible to follow a vegan KD, it certainly isn’t easy and you could easily end up being deficient in certain nutrients.
Does a KD have an impact on sports performance? From the discussion so far, it would appear that in theory, if a KD could boost fat metabolism and generate a unique fuel source via ketone bodies, whilst eradicating the need to fuel on carbohydrate sources during long endurance efforts, this could indeed be the breakthrough that Sports Scientists and athletes alike have been looking for. There are certainly numerous anecdotal reports from those who have pursued a KD and have taken to the internet in a rather evangelistic manner to proclaim the benefits. When we published our Fasted Training or ‘Training Low’ article a couple of years back, we engaged many people on social media with a fascinating debate on the subject and this was in a large part why we have decided to produce this piece as a follow up. We too were fascinated by the commitment to the cause. People have strong views on a variety of topics, we’ve learned that from Brexit, but now more than ever, these discussions need to be evidence-based and that’s what we’ve always been very careful to do here at TORQ. Just because someone thinks it’s a good idea or have convinced themselves that it’s the right thing to do, doesn’t mean that the research supports it. The problem is that if we’re looking for scientific evidence to support the virtues of a KD, many researchers traditionally seem to be firmly in 2 camps, both in their own echo chambers, but as we eluded to a few of years ago in our Fasted Training piece, there are those willing to consider compromise and look at a more nuanced approach. The problem is, a KD is not nuanced, it’s very definite and very extreme in its rules and structure. On balance, there is no one that could argue that the research supporting a high carbohydrate diet doesn’t eclipse that supporting a KD, but that’s not to say that we shouldn’t work through the arguments for and against in a logical fashion and that’s what we’re doing here.
What appears to be clear is that a KD does in fact alter the way that the human body processes energy, there’s no doubt that this is the case. If you follow a KD, you will improve your ability to burn fat, you will burn ketone bodies and you will lose your dependence on carbohydrate as an energy source. This could have potentially positive implications for self-supported ultra-endurance events. For instance, Venebles et al (2005) suggest that: ‘It’s exceptionally well documented that when carbohydrate availability is restricted, especially over sustained periods of time (weeks) skeletal muscle will adapt to metabolise greater quantities of fat at the same exercise intensity. This may have implications for certain ultra-endurance events that are self-supported at relatively low intensity. Having the capacity to regulate a consistent workload hour upon hour could prove beneficial against those having to fuel regularly in order to maintain even a light to moderate workload as glycogen supports fat metabolism with the demand for aerobic fuel production.’
In essence, even back in 2005, researchers recognised the human body’s ability to adapt to burning fat more efficiently in the absence of carbohydrate, so a KD certainly holds some appeal should you be planning on taking part in an event like the Tour Divide for instance, where the traditional route of fuelling regularly with carbohydrate sources could be somewhat impractical. Essentially, a KD has legs if the endurance performance is extremely long and sustained and foods/drinks containing carbohydrate can not be easily accessed or relied upon. This could however lead to digestive problems or ‘rejection of carbohydrate’ if the athlete has no option to consume carbohydrate foods at times, which suggests that a more metabolically flexible approach might be more useful. In better known mainstream ultra-endurance events like IronMan Triathlon or the Tour De France the argument to follow a KD is far less convincing. In these events, carbohydrate fuelling products like the ones we produce at TORQ are readily available and are widely used by World Class athletes. There’s no argument against the notion that a KD adapts one’s body to utilise energy in a ‘different way’ but there is no evidence that this produces better endurance performances than those performed by someone on a high carbohydrate diet providing they have access to fuelling products. Furthermore, and this is the clincher, a KD downgrades the metabolic pathways responsible for carbohydrate metabolism on the basis that carbohydrate has been completely removed from the diet. This is the age-old biological principle of stimulus-response or ‘use it or lose it’ in layperson’s terms. If you remove carbohydrate from the diet, the absorption and processing pathways have no reason to exist, so they ‘wither on the vine’ so to speak. If the human body can’t process carbohydrate, then it will have no anaerobic energy system and with no anaerobic system, there is no top-end power or sprint. Since practically every event is won or lost from a sustained burst of power or sprint finish, there really is no compelling argument for following a dietary regimen that allows someone to ‘almost win.’ A KD might get you close to the finish line in touch with the leaders, but then you simply won’t be able to respond to the change in pace necessary to get you across the line first. An example of the importance of the anaerobic energy system plays in winning races was evident in this year’s Giro D’Italia, which finished literally 2 days ago at the time of writing this, where the winner Geoghegan Hart, took advantage of the final Time Trial to claim victory. The high sustained power output required to win the 15.7km time trial simply wouldn’t have been possible without a highly-tuned carbohydrate-burning anaerobic system.
In support of this, Pinckaers et al (2017) reported that: “Road race cycling also includes repeated sprints and periods of increased workload that exceed an athlete’s maximal aerobic power. These periods of increased exercise intensity often determine the eventual race outcome. Under such conditions, a reduction in glycolytic capacity* may compromise an athlete’s specific energy needs during competition.” *Glycolytic capacity, essentially means the same thing as anaerobic capacity. As previously stated, there is a mountain of research data supporting the vital role carbohydrate plays in the anaerobic energy system – too many studies to mention here. Is a KD practical? We are an incredibly adaptive species. Just as our metabolisms can adapt to cater for different fuel sources, emotionally we can adapt to unusual circumstances, especially if we’re motivated to do so. With a little research, most people should be able to make the necessary dietary changes to ‘go keto’ but gone will be the days that you can eat a little bit of everything or go to a restaurant and order whatever you fancy off the menu. You’re certainly not going to be treating yourself to a hot chocolate fudge cake for dessert! If you’re vegan or follow a plant-based diet (we will refer to this as PD from this point onwards), you will have already adapted to your unique set of circumstances, so can you adapt further and go PD KD – it might be a tall order? Let’s be clear about this, a KD isn’t practical. Of course it can be done, but a pragmatist would always ask the question why? If there is no evidence of a performance advantage from adopting a KD and there is clear evidence that it’s going to stop you winning races, why would you put yourself through it? It then becomes a question of an individual’s motivations and perhaps their refusal or inability to accept the evidence. Is a KD healthy? At the start of this article we listed a number of clinical applications for a KD and it would be wrong to ignore the prescriptive benefit of this kind of diet to specific populations in particular circumstances, but it would be a sweeping generalisation to suggest that the diet is on the whole healthy. We also discussed earlier how there can be different interpretations as to which foods should be consumed on a KD. Protein/fat sources such as chicken, salmon, tuna, nuts and seeds and pure fat sources such as avocado and olive oil sit more comfortably under the ‘healthy umbrella’ than foods such as bacon, sausages, red meat, cheese and butter – foods that not so long ago we were told would block our arteries and kill us! Let’s look again at the PD. We have conceded that, with some effort, someone following a PD could also follow a KD, but this really would represent the exception to the rule. Most PD’s are by definition very high in carbohydrate and low in fat and this assertion is supported by Tuso et al (2013) who suggest that: ‘Typically, plant-based diets tend to be higher in complex carbohydrates, and lower in saturated fats due to the nature of the food sources.’ Singh and colleagues (2003) also suggested, after reviewing 87 published studies, that vegan or vegetarian diets have been proven to be very effective for weight loss and reducing heart disease, high blood pressure and diabetes. Studies in this review also linked red meat consumption to increased cardiovascular mortality. One can’t even begin to imagine the debate that would kick off if a group of evangelistic KDs were placed in the same room as a similarly committed bunch of PDs! If you’re following a PD you won’t necessarily be following a ‘healthy diet’ either, because without special attention, you could certainly be deficient in certain nutrients. Vitamin B12 and Omega 3 essential oils being the 2 most prominent according to research by Davis & Kris-Etherson (2003). And of course, as we mentioned earlier, care needs to be taken to ensure adequate protein intake and to include the full array of essential amino acids. So what is healthy? To truly define health, surely the best marker of this is longevity – how long do people live for on different diets and fortunately there is clear evidence available. There are regions around the globe which have been defined as Blue Zones and these represent areas where people have the longest life expectancy in the world. The Blue Zone regions’ diet provides a distinct contrast to a KD and originates from 5 countries located longitudinally, positioned within the middle of the globe covering; Loma Linda USA, Nicoya Costa Rica, Sardinia Italy, Ikaria Greece, Okinawa Japan. Typically, a blue zone diet consists of 95% plant-based foods, with only 5% coming from animal-based foods. However, an important rule is that animal proteins from meat are generally considered as a “no go” area and should not be consumed more than twice per week. However, animal proteins in the form of dairy and eggs are acceptable, but should be limited. From this diet, we see a large % of foods coming from carbohydrate (65%), fats (20%) and protein (15%), which clearly contradicts that of a KD.
Image from bluezones.com The Blue Zone diet came into the public spotlight back in 2005 when the National Geographic Magazine published an article called “Secrets To A Long Life”, which discussed how the number of people living beyond 100 years old consumed this high carbohydrate yet vegetable-based, Mediterranean-style diet across this regional Blue Zone belt. When breaking down the composition of the Blue Zone diet, it highlights a very rounded and balanced diet which would include a vast array of vitamins and minerals from the selection of beans, pulses, legumes, fruits, oats and nuts which will also help to deliver the desired amount of fats, carbohydrates and proteins/amino acids. Although animal proteins from meat are typically ‘no go’, the phrase ‘fish is fine’ is well accepted within a blue zone diet. The assumption for this, after examining the remainder of the Blue Zone diet is likely due to the lean source of protein, whilst still containing adequate essential fatty acids required for cellular communication, brain development and management of blood cholesterol from omega-based unsaturated fatty acids. It’s fair to say that the lifestyle habits of the populations consuming a Blue Zone diet is very different to millions of people living within stressful, first world environments and so we cannot solely attribute a population’s health and longevity to the food consumed, but the evidence certainly doesn’t support a KD and its fair to say that independently we all need to take a look at how we live our lives, not just at our diets.
Is a KD ethical? We really don’t want to dwell on this subject, because we really do appreciate an individual’s right to make his or her own choices. At TORQ, we are educators in human performance and health, we’re not politicians. We consider ourselves an ethical company and the reason many of our products are certified organic by the Soil Association is because we believe in the quality and sustainability of organic produce. We also believe that we all need to make decisions that support each other and the environment we live in. One area that we need to address as a global population is the amount of meat we consume. We’re not suggesting that everyone needs to become vegan or vegetarian, but if everyone ate less meat, the planet will thank us for it and it would help us to move towards vital biodiversity and sustainability. To this end, it does seem that a significant amount of focus would be required to ensure that a KD met these criteria. It’s certainly not impossible, but a lazy attempt at a KD could easily compromise this ethical consideration.
Conclusions According to research, a KD, if properly adhered to, will induce ketosis within 4 days. This has been proven to change the metabolic pathways within the body, encouraging the utilisation of fat as a fuel and produces ketone bodies, which can also be used for energy. There can be no doubt that these transformations take place. From a clinical perspective, it appears that a KD may be useful in certain specific situations to reduce cellular inflammation during periods of illness and there is also evidence to support the role of a KD in the treatment of epilepsy and Alzheimer’s disease as well as potentially helping with the management of Type 1 diabetes. From a sports performance perspective, the most relevant application of the KD would be towards unsupported ultra-endurance type events where sources of carbohydrate fuel may be scarce or unreliable. With regard to mainstream endurance events/activities, whilst a KD could provide ‘another way’ of fuelling one’s performance, there is no evidence to suggest that it offers any performance benefits over a regular high carbohydrate diet, providing the athlete is able to access carbohydrate based energy products. In fact, it’s clear that races are either won or lost due to a surge in anaerobic power, particularly in the closing stages of a race, so an athlete fuelled on carbohydrate has this distinct and essential advantage. From a health perspective, other than for specific clinical conditions, it is hard to justify a KD as being ‘healthy’ as such. There are certainly healthier choices that can be made within a KD, but the evidence supporting much higher carbohydrate diets in the Blue Zones around the world is difficult to ignore. At TORQ, we have gone on the record on many occasions to make our opinions clear and that is that we believe in organic produce where possible from a health and ethical perspective. We also believe that everyone should eat less meat and should consume plenty of fibrous fresh fruit and vegetables. From a performance perspective, we do believe in dietary manipulation and a nuanced approach to encouraging fat burning, whilst maintaining the ability to burn carbohydrate via a highly functional anaerobic system – called ‘metabolic flexibility’ and consuming ‘fuel for the work required.’
We’ve said it before and we’ll say it again, keep moving, stay fit and the statement ‘fuel for the work required’ really says it all – enjoy a mixed balanced healthy diet and consume the calories your body needs based around the amount of physical activity you’re doing. If you found this article interesting and would like to learn more about how to get the most out of all your body’s energy systems, please read Fasted Training or ‘Training Low’. If you have any further questions about this article or any others, please do not hesitate in contacting us on 0344 332 0852 or email firstname.lastname@example.org
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