Ketones – More endurance & a clearly optimised fat metabolism through ketone drinks?! Studies, effects & background

87 hours, 20 minutes and 5 seconds – for 3470 kilometres. In 21 days. These are the data of the winner of the most important cycling race in the world in 2020. The data of Tadej Pogacar. The then 21-year-old Slovenian won the overall classification of the Tour de France by 59 seconds. Less than a minute – after 3470 kilometres. This shows that during a cycling race one thing counts above all: every second counts. Every small improvement, every “marginal gain” can be a step towards success – in training, in regeneration, aerodynamics, weight, material, nutrition. The latter has been influenced for some years by a new development and the question of the effects of the body’s own substances on performance: What are ketones and what do they bring? There is much to be said for positive effects on certain areas of performance. Fact is: ketone drinks are becoming more and more widespread in the professional peloton. “Ketones are food supplements. The substance is not on the banned list. Several teams are known to use them,” says Jumbo Visma team manager Richard Plugge. “You can take them like vitamins.” Still, for some experts – because of their potentially performance-enhancing effect – they are on the borderline of doping. In 2018, Italian professional rider Vittoria Bussi broke the world hour record. She completed 48.007 kilometres in 60 minutes after consuming ketone drinks throughout her preparation. The desired effects of ketone bodies have already been proven in small studies: optimised fat burning, sparing of carbohydrate reserves during exercise – as well as increasing insulin sensitivity and the ability to regenerate.

Ketones are substances produced naturally in the body during the breakdown of fatty acids in the liver. They are energy carriers that are formed from fat in the liver under starvation conditions – when no more carbohydrates are available – and metabolised for energy production. The body also makes use of ketones during birth and in the first few months afterwards to enable the brain to grow quickly. “Ketones” is a term for all chemical compounds with a specific molecular arrangement of oxygen and carbon. Strictly speaking, in the context of human metabolism, we should speak of “ketone bodies”. The term ketone bodies includes both ketones and a chemically slightly modified form of them. Three ketone bodies are formed in the body: acetone, acetoacetate and beta-hydroxybutyrate. The first two are ketones by definition, the third has a slightly modified molecular structure. This is the most potent ketone body for providing energy and is most abundant in the body. Acetone cannot be utilised by the body and is excreted through the urine or breath. The organism, the human “engine”, can obtain its energy from three fuels: Carbohydrate, fat – and ketone bodies. The glucose energy supply is quickly available, but severely limited. Trained athletes can store a maximum of up to 600 grams of sugar. The fat supply, on the other hand, is almost “unlimited”, even in lean people. Energy production from body fat has two disadvantages: Firstly, the conversion takes longer, and secondly, the brain “runs” on carbohydrates. Fatty acids cannot penetrate the blood-brain barrier – with one exception: the so-called MCTs, medium chain triglycerides. If the glucose stores are empty, a process can occur that athletes in particular want to avoid: gluconeogenesis, the formation of new glucose, among other things through the breakdown of muscle protein. In addition, during such a state of hunger, the body starts producing ketone bodies from fat. These supply the brain with energy and are also available to the other body cells as a quick-acting source of energy. These ketone bodies produced by the body are called “endogenous ketones”. Those supplied from outside are called “exogenous ketones”.

Exogenous ketones have been used for decades. In the beginning, their production was extremely expensive. Initially, the use of exogenous ketones was limited to sectors such as space travel and the military. In medicine, they have been used for years, especially to treat epilepsy or mental disorders. Taking ketones can lead to positive metabolic changes: for example, improved mitochondrial function and anti-inflammatory processes. Animal studies also showed a reduction in blood sugar. Initial pilot studies on humans delivered positive effects with regard to combating obesity as well as against a lack of energy in the brain in dementia diseases. So far, only the so-called beta-hydroxybutyrate, BHB, has been used as a food supplement. These exogenous ketones are only indirectly effective. The body produces only dextrorotatory BHB in the liver, while levorotatory BHB is often found in food supplements. However, the body needs dextrorotatory BHB for rapid energy production. Dextrorotatory BHB is either converted into the dextrorotatory form in the organism or excreted completely because it cannot be utilised. Long before there were exogenous ketones, people tried to stimulate the body to produce ketone bodies. The means to do this was: the ketogenic diet. During certain phases, carbohydrates were largely avoided. The aim was to get the body to produce ketone bodies. The ketogenic diet is not the same as modern low-carb diets. With these, the body is not usually “forced” to produce ketone bodies. However, if carbohydrates are limited to an unavoidable minimum, ketone bodies are formed in the liver. The maximum amount of carbohydrates consumed varies from person to person, between 20 and 50 grams per day. If increased levels of ketone bodies are detected in the blood, this is called a state of ketosis. In a normal state, this concentration is between 0.05 and 0.1 millimoles per litre of blood. In the state of ketosis, the values are between 0.5 and five millimoles. Caution: At the beginning of a ketogenic diet, the organism may have problems producing sufficient ketone bodies. If this is the case, one temporarily suffers from the consequences of food deprivation. The technical term for this is: “keto flu”. Exogenous ketones are now also used to bridge this condition.

The ketogenic diet is controversial – among other things because it can cause a possible increase in the “bad” LDL cholesterol. This is suspected of causing cardiovascular diseases. Type 1 diabetics are a special case. Since their pancreas cannot produce insulin and the body cells usually cannot absorb glucose independently of insulin, a lack of energy in the cells leads to the production of ketone bodies. In a diabetic, the regulatory mechanisms through insulin are missing and too many ketone bodies can be produced, which causes the pH value of the blood to drop and can lead to hyperacidity. In extreme cases, this can be life-threatening. Therefore, diabetics should measure their ketone levels from time to time.A remedy that more and more amateur and hobby athletes are also using to optimise their fat metabolism is called: fasting training. You train in the morning before breakfast for 60 to 90 minutes in the basic range. The effect: due to the lack of carbohydrates, the body produces ketones. However, the extent of this production is – in relation to a fasting diet or a ketogenic diet – much lower. The use of ketones in sports can serve different purposes. On the one hand, they can potentially support the weight loss process. This is because during a significant weight loss phase, energy deficiencies and drops in performance can occur. Among other things, ketones can curb the feeling of hunger by reducing hunger hormones such as gherlin. In addition, they can be used to supply the brain with energy during training without the need for carbohydrate intake. Consuming glucose causes a noticeable rise in insulin, which slows down or can even “shut down” fat burning. With ketones, fat burning continues and is even “boosted”. Muscle breakdown during fasting workouts can also be prevented because ketones stop gluconeogenesis. When taking exogenous ketones during a competition or training, the body primarily resorts to these substances for energy production. In this way, the carbohydrate stores are spared. At the same time, fat oxidation can be increased, which in turn reduces the proportion of sugar in energy production. Several studies – for example, those of the University of Leuven – showed that ketone intake during intense exercise leads to a significant decrease in lactate concentration.

This study shows that ketone intake after a training session is associated with an increase in glycogen synthesis. A fact that can contribute to improved recovery. Dr. Brianna Stubbs from Oxford University and other scientists note in their study that muscle tone is lowered and blood vessel formation is stimulated after ketone ingestion. Biomarkers associated with cardiovascular stress and heart failure are reduced. Studies – such as those by Peter Hespel and others – also showed that the risk of overtraining can be reduced by intensive or extensive sessions. In competitions, not only the physical but also the mental demands are high. A study by the University of Madrid showed that ketone intake can also support this – in the form of an improved energy supply to the brain. The researchers found increased concentration and improved mental focus in their test subjects. But: Ketones are not a miracle cure. The picture regarding potential performance enhancements is mixed. For example, it has not been proven that taking ketones has an effect on performance during short periods of high-intensity exercise – despite a frequently observed reduced lactate concentration in the blood of the test persons. A large-scale study by the two researchers Brendan Egan and Dominic D’Agostino, which appeared in the scientific journal “Cell Metabolism”, is dedicated to the use of exogenous ketones in high-performance sports. The result: An average performance improvement of two percent was found during a simulated time trial on the cycle ergometer. An extreme increase in average performance of 15 percent during a 30-minute exercise after taking ketones was also shown in the study by the University of Leuven. As a possible side effect of taking exogenous ketones, gastrointestinal complaints have been reported so far. The complaints that occurred, such as nausea, flatulence or diarrhoea, were above all also dependent on the type of preparation used and also occurred in carbohydrate drinks tested in parallel. A 28-day study by researchers at Oxford University, in which the test persons took ketones three times a day, showed no change in physiological parameters or changes in the tested blood and urine values. Long-term studies on the topic of “ketones in sport” are still lacking. Initial study results show potentially positive effects such as: reduced lactate formation, increased fat oxidation, sparing of glycogen stores and improved regeneration. However, the findings regarding performance improvements are inconsistent.

Interview: Dr Philipp Wagner, sports physician

Mr Wagner, more and more WorldTour teams have been using them for a few years. Are ketones just a “trend” – or more than that?

From my point of view, ketones belong to a group of substances that deserves high attention in the sports and medical field for future investigations. Basically, we always move outside the natural range as soon as we need supplements for sport. It doesn’t matter whether the supplements are called ketones or sugar. Ketones are exciting because they lower blood sugar compared to sugar-only supplements. Endurance athletes also endanger their health in the long run by sugar excesses – before, during or after exercise. Even if performance increases as a result.

How much research has been done on the effects of ketones?

It is only at the beginning. I have found numerous studies, but the significance of each is limited. Large studies with several thousand test persons over several years would be necessary to filter out real class effects. So far, it is more a matter of approaches, ideas and observations. Ketones are supposed to reduce oxidative stress, improve blood sugar levels and mitochondrial and brain function. But there are also quite contradictory results on this.

What potential does the ketogenic diet have for athletes?

I see the ketogenic diet as a great opportunity and an important building block in the treatment of metabolic diseases such as type 2 diabetes, high blood pressure, obesity with corresponding joint problems – and as an interesting option for brain diseases. The frequently reported negative effect of increasing blood lipids can be observed easily and very cheaply at the doctor’s office. However, people with hereditary high cholesterol levels have to be very careful. Regular exercise, especially in the low-intensity range, burns the blood fats and can solve this problem to a large extent.


This article is an excerpt from the original article published in the RennRad 05/2021 issue of the German RennRad magazine. The issue can be ordered here.*

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