WHAT EXPERTS SAY
What is ketosis?
A METABOLIC STATE
The ketosis
Ketosis is a metabolic state in which the body obtains energy from burning fat. It is therefore relevant for nutritionists, as well as for anyone who wants to improve their health and/or lose weight. But how exactly does ketosis work? What are the associated benefits and risks, and how is it possible to achieve this metabolic state? Read on to find the answers.
How does ketosis work?
Our metabolism is mainly fuelled by carbohydrates, or more precisely, glucose molecules. The body stores excess glucose that is not immediately required in the liver and muscle tissue. If these so-called glycogen stores are exhausted – e.g. due to prolonged periods without food, a ketogenic diet or intensive training – and are not replenished in the form of a carbohydrate-rich meal, the body gets the energy it needs in other ways and is forced to mobilise its fat reserves. The fat cells release the stored fatty acids into the bloodstream, which in turn distributes them to the body’s cells. In short, if the body is no longer supplied with glucose, it uses fat stored in the body.
What sounds like a practical and simple solution is actually a complex process. Because while most body tissue (such as the skeletal muscles, heart muscle, kidneys and liver) can also convert non-water-soluble fatty acids into energy, certain other tissues, in particular the brain, cannot. To supply these cells with nutrients, the liver converts fatty acids into smaller molecules, called “ketone bodies”. The most important of these are beta-hydroxybutyrate (BHB), acetonic acid and acetoacetate. Unlike fatty acids, ketone bodies can pass through the blood-brain barrier.
This metabolic state with an increased concentration of ketone bodies in the blood and in the intercellular space is called ketosis. The more ketone bodies there are in the blood, the more will also pass through the cell walls to the organs. However, around 5 percent get “lost” and are excreted in the urine, which is why ketone test strips can be used to measure whether you are in ketosis or not.
Gradually, the cells “learn” to convert ketone bodies into energy with the help of enzymes: The metabolism has switched from burning sugar to burning fat. This is also known as a “metabolic switch”.
Ketosis allows sparing muscles
A common myth suggests that fasting can be dangerous because the body breaks down muscle proteins for energy, leading to muscle loss. This belief arises from a misunderstanding of how the body uses different energy sources during fasting. In the first two days of fasting, only a minimal amount of body protein is used for glucose production. However, fat becomes the primary fuel for energy production during fasting, which explains why both animals and humans experience no significant reduction in muscle performance while fasting.
Methods to enter ketosis
One way to achieve and maintain this “metabolic switch” that has been popular in weight loss and fitness forums for some years now is a so-called ketogenic diet or “keto diet”. Basically, this is a radical version of a low-carb diet that has been around for some time now, with an even fewer carbohydrates and more fats and proteins. Originally developed to treat epilepsy, this form of nutrition is often combined with intermittent fasting according to the 16:8 principle, in which you leave out breakfast, for example, to enter ketosis even faster.
A classical ketogenic diet comprises 80 to 85 percent fat, 10 to 15 percent protein and around 5 percent carbohydrates. Sweeteners and cereals, pulses, starchy vegetables such as potatoes, sweet potatoes and corn, as well as fruit that is high in sugar (such as bananas, pears, mangoes, grapes, pineapple and sweet cherries), snacks, sweetened dairy products and drinks are prohibited. This form of nutrition is not a problem as a short-term measure for healthy adults, for example as an introduction to a healthier, lower-carbohydrate diet. However, apart from reducing weight and body fat, the health benefits of a longer-term ketogenic diet are debated.
Since a ketogenic diet requires considerable knowledge, is time-consuming and generally difficult to maintain in a social context with family and friends, it is hardly surprising that an increasing number of more or less reputable suppliers of nutritional supplements are cropping up, particularly on the internet, that supposedly help you to achieve a state of ketosis without the restrictions and disadvantages mentioned above. However, it has not yet been convincingly proven that these supplements, called exogenous ketones, which are popular in competitive sports, have the same positive effects as the (endogenous) ketone bodies produced by the body itself and that they are as effective and safe to use as the suppliers claim. It is not uncommon for these powders or “ketone drinks” to also contain other, often dubious ingredients and additives, which is why consumer protection organizations currently advise against buying and consuming such products.
A method to achieve ketosis that is demonstrably healthy, safe and highly effective is fasting – either in the form of classic therapeutic fasting in a clinical setting, or with the newer at-home fasting programme Buchinger Wilhelmi Fasting Box that allows a slightly higher calorie intake of around 600 kcal per day compared to conventional fasting, but with a strictly limited amount of carbohydrates in favour of vegetable protein and healthy fats. Other diets called fasting-mimicking diets are designed to mimic the effects of fasting while still allowing for solid food intake, providing around 800 calories per day.
The scientific team at our clinic has since carried out several studies on this subject that prove the effectiveness and the many positive health benefits of fasting. For example, an extensive study on the role of ketone bodies in long-term fasting published in the renowned scientific journal Nutrients showed that most of the 1,610 participants, who fasted for 4 to 21 days in accordance with the Buchinger Wilhelmi fasting programme, reached ketosis as early as the second day of fasting and benefited from the health effects of this metabolic state.
Another study, the results of which will soon be published, investigated fasting with the Buchinger Wilhelmi FASTING BOX, a five-day modified fasting programme which can be done at home. Again, all participants achieved ketosis.
Health effects of ketosis
Many people who fast not only visibly lose weight, but also see a decrease in visceral fat. This is the abdominal fat that surrounds the internal organs, especially the digestive organs. It produces, among other things, harmful fatty acids and inflammatory messenger substances that increase the risk of type 2 diabetes, non-alcoholic fatty liver disease and cardiovascular disease. One of the many positive effects of ketosis is to activate autophagy, in which damaged cell components are broken down and recycled to generate energy. The underlying mechanism was first described in the 1960s, and Yoshinori Ohsumi was awarded for his work on it with the Nobel Prize in Physiology or Medicine in 2016.
The term autophagy is derived from the Greek autóphagos – “self-devouring” – and refers to a kind of endogenous waste disposal system: The waste that accumulates over time in the cells is separated and then broken down into its components by enzymes. The part that can be reused is recycled and the rest excreted. Ketosis or autophagy therefore play a key role in maintaining good health. By breaking down junk in the cells, they ensure that these can continue to fulfil their task properly. And as viruses, bacteria and other microorganisms are also filtered out during autophagy, they play an important role for the immune system.
Ketosis could also be relevant in the prevention and treatment of neurodegenerative diseases such as Parkinson’s disease, Multiple Sclerosis and Alzheimer’s, as increased autophagy inhibits the destruction of nerve cells in laboratory animals. A ketogenic diet (under strict medical supervision) is now recognized worldwide as a treatment for drug-resistant epilepsy in children and adolescents, but adults also appear to benefit from it. Scientists assume that ketosis boosts the generation of energy in the brain and stimulates the formation of an inhibitory neurotransmitter (GABA).
Many people who fast also describe having more energy, greater mental clarity and better concentration. The reason for this seems to be an improved energy balance in the brain caused by ketosis: the ketone bodies modulates the function of the nerve cells and this could be hypothesized to explain the improve mental capacity during fasting.
Risks and side effects of ketosis
The metabolic change to fat burning can lead to temporary side effects which are known as “Keto flu”. This refers to a collection of flu-like symptoms — such as headaches, fatigue, irritability, dizziness, nausea, and muscle cramps — that some people experience when starting a ketogenic diet, as the body transitions from using carbohydrates for energy to burning fat, leading to temporary electrolyte imbalances and dehydration.
The long-term sides effects of a ketogenic diet can be more serious if this is causing nutritional deficiencies. For example, nutritionists criticize the high content of animal protein and, in some cases, saturated fats and point to the risk of nutrient and fibre deficiencies due to the unbalanced diet. In the worst case this can even lead to kidney damage. Therefore, if you want to follow a longer-term ketogenic diet, you should do so under medical supervision and guidance.
In addition, especially people who suffer from type 1 diabetes run the risk of so-called ketoacidosis, an excessive acidity of the blood due to the accumulation of ketone bodies, which can lead to diabetic coma if left untreated. However, let’s not counfound nutritional ketosis with ketoacidosis. Although the level of ketone bodies in the blood can be comparable in both cases, nutritional ketosis during fasting is self-controlled and does not cause any of the side effects seen in the uncontrolled ketoacidosis which is a pathological condition.
In our study we compared measuring with ketone test strips with the more invasive blood test and determined that the results were highly consistent. Whatever the method, it is important to measure for ketosis at roughly the same time each day.
The results of the measurement of ketosis in urine can be interpreted as follows:
- 5 mg/dL: minimal ketosis
- 15 mg/dL : slight ketosis
- 40 mg/dL : moderate ketosis
- 80-160 mg/dL : high ketosis
Tips for fasting successfully
Fasting usually lasts between 7 and 21 days at our clinics (plus digestive rest days and days in which you gradually reintroduce food after fasting). To prepare your body for the metabolic switch and prevent headaches, you should start reducing your consumption of addictive substances such as alcohol, coffee and/or nicotine and refined sugar around a week before starting the programme. Digestive rest days are also very important as a transition to help you adjust. On max. two days, eat light meals with small portions (e.g. steamed vegetables, fruit or yoghurt). Avoid alcohol and nicotine from now on. If you want to save yourself the trouble of lengthy planning, we recommend the Buchinger Wilhelmi FASTING BOX – a five-day reset programme to do at home that quickly gets you into ketosis and is ideally adapted to the body’s needs.