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