A keto diet is the term used to describe all diets that manage without carbohydrates to the extent that a so-called “ketosis” is generated. When this metabolic state occurs, the body covers most of its energy needs from fats. Find out what happens in the body during ketosis and how healthy a ketogenic diet is for you!
A ketogenic diet is a diet in which few carbohydrates (“low carb”) to very few carbohydrates (“no carb”) are consumed. This means that the daily diet consists mainly of fish, meat, seafood, dairy products, nuts, kernels, legumes and low-sugar fruits and vegetables. On the other hand, foods with a high concentration of carbon hydrate, such as cereal products or potatoes, are avoided.
The aim of a ketogenic diet is to put the body into a special metabolic state called “ketosis”. This condition occurs when very few carbohydrates are added to the body (less than 50 g per day) and it has used up its glycogen stores (takes about 2 to 3 days).
If a ketogenic diet is also accompanied by a calorie deficit, then it is a diet that will inevitably lead to weight loss. The ketogenic diet can also be implemented with a balanced or positive calorie balance (see anabolic diet). In this case, the focus is not on fat loss, but on other goals such as the treatment of certain neurological and metabolic diseases or muscle building.
Since the available amount of carbohydrates is the only decisive factor for the onset of ketosis, the terms “ketogenic diet”, “low carb” or “no carb diet” and sometimes “paleo diet” are often used synonymously. Well-known diet forms of the keto diet are, for example, the “Atkins Diet”, the “New York Diet” or the “South Beach Diet”.
In short, the assumption of all ketosis diets is that it is the carbohydrates that make us fat, because they lead to a more or less high level of insulin and, among other things, insulin ensures that body fat is formed. On the other hand, a low insulin level creates a hormonal environment in which body fat can be broken down.
What is ketosis?
Ketosis is a special metabolic state that enables the body to cover its energy mainly by breaking down fatty acids. Normally this is not possible because “fats burn in the fire of carbohydrates”, as it is called in the professional world. Why?
To generate energy, carbohydrates are first broken down into glucose (grape sugar) and then further into pyruvic acid (pyruvate). This in turn is converted into activated acetic acid (acetyl-coenzyme A), with oxaloacetic acid (oxaloacetate) being produced as a by-product. Fatty and ketogenic amino acids are also broken down into acetyl-coenzyme A for the purpose of energy production, but without the formation of oxaloacetate.
Acetyl-coenzyme A can only take part in the further energy metabolism process (citric acid cycle and respiratory chain) if sufficient oxaloacetic acid is available. If this is not the case, precisely because no carbohydrates but only fatty and ketogenic amino acids have been broken down, access to the citric acid cycle is, so to speak, blocked for the acetyl coenzyme A.
The body reacts and redirects acetyl coenzyme A to the liver, where it is broken down into the three ketone bodies acetoacetate, beta-hydroxybutyrate and acetone. The latter no longer plays a role in the further metabolism and is excreted through the kidneys or urine or exhaled through breathing (smellable).
Acetoacetate and beta-hydroxybutyrate, on the other hand, are energy carriers, whereby the energy cannot be released in the liver itself. Therefore, these two ketone bodies are transported to other organs via the blood. At the destination, the ketone bodies are converted back into acetyl-coenzyme A and then fed into the citric acid cycle.
Via the detour of ketosis, the body can use fatty acids and ketogenic amino acids effectively to generate energy without carbohydrates or oxaloacetic acid. Organs like the brain, which, unlike muscle cells, for example, normally get their energy exclusively from glucose and not alternatively from fat, benefit from this.
Ketosis can be demonstrated by the characteristic acetone odor of the breath and in the laboratory: test strips can be used to detect ketone bodies in the blood and urine (ketonuria) (nitroprusside method).
This is how you get into ketosis
While some organs such as muscles can get their energy from both fat and carbohydrates, other organs such as the brain are normally dependent on energy from carbohydrates in the form of glucose. The minimum daily glucose requirement of an adult is therefore around 200 g.
If the food does not provide this amount of glucose, the body first uses its own glycogen, i.e. carbohydrate stores. When these are empty, it begins to produce glucose in the liver and kidney cortex itself (gluconeogenesis), mainly from amino acids (protein) that come from food and muscle breakdown. Part of the required glucose can also be synthesized from glycerine (fat). The body can produce as much glucose as it absolutely needs to survive, around 200 g per day.
If the carbohydrate deficiency continues, however, he gets a problem, after all, he is constantly breaking down muscles in order to turn them into glucose. And he needs muscles to survive too. The organism reacts by switching its metabolism to ketosis, because with the ketone bodies it can supply the central nervous system with energy that does not come from glucose. So the muscles (protein stores) are spared. The operation of the muscles can also be covered with body fat without ketosis – at least if the loads are not very intense.
So you get into ketosis when you hardly consume any carbohydrates and wait for your glycogen stores to empty. The longer you maintain this state, the more your metabolism changes: If the body itself produces around 150 g of glucose per day at the beginning of a carbohydrate-free period, it is only around 25 g after 5-6 weeks.
How much fat do you eat?
If you want to have a functioning ketogenic diet, you not only have to reduce the carbohydrates to below 50 g per day, but also keep the protein consumption moderate, because the body can produce glucose from protein, which prevents the onset of ketosis.
In a classic ketogenic diet, the daily calories are roughly distributed among the individual macronutrients: 90% fat, 8% protein and 2% carbohydrates.
Can You Lose Weight Fast On A Keto Diet?
You can often read that you can lose weight particularly quickly through ketogenic diets and the resulting ketosis. Practice seems to confirm this – at least if you only go on a diet for a few weeks: the pounds drop faster than with low fat diets.
However, if you look at longer periods of time, the picture changes. The differences between the diets are barely noticeable: ketogenic diets such as low carb and the previously more popular low fat diet lead to similar weight losses and similar yo-yo effects.
But why does the ketogenic diet work especially at the beginning?
Water loss at the beginning of the ketosis diet
The main reason for the relatively high weight loss early in the ketogenic diet is the depletion of glycogen stores in the body. All carbohydrates are first broken down by the body into glucose (grape sugar) and then either consumed or stored as glycogen in muscles and liver.
This glycogen in the body, which adds up to 200-400 g in total, binds another 600-1200 g of water. When the storage tanks are empty, the bound water is also excreted. There is a corresponding weight loss. If you eat carbohydrates again, the glycogen stores fill up again and water is bound again. The weight goes high.
The calorie deficit is decisive
Some descriptions of the ketogenic diet give the impression that ketosis is crucial for the loss of body fat. But that is not correct: If carbohydrates are missing as energy suppliers, the organism burns more fatty and amino acids, but these can just as well come from food as from its cells.
If the energy balance is balanced or positive, i.e. if enough or excessive calories are ingested through the consumption of fat and protein, the body does not need to tap into the fat cells in order to maintain its operation – ketosis or not. How much fat you burn on ketogenic diets is mainly decided by the calorie deficit.
What can I eat on the keto diet?
There are no “ketogenic foods” in the strict sense, because it is your body in which ketosis occurs. However, in a certain way one can speak of “ketogenic foods”. One then means all foods that do not stand in the way of ketosis, i.e. foods without carbohydrates or those that contain only a few.
What are the risks of the ketogenic diet?
The ketogenic diet is very specific and controversial. Experts sometimes classify it as “malnutrition” because not enough fruit and vegetables are consumed to cover the need for vitamins and nutrients. A sufficient supply of dietary fiber is also not guaranteed without further ado. For this reason, some institutions explicitly advise against “extremely low-carbohydrate and one-sided diets”.
From a medical point of view, the following risks and side effects of ketogenic diets are discussed or assumed:
- Increase in cholesterol
- Kidney damage
- Increased risk of cancer (breast and colon)
- Bone damage
- Heart disease
- Bad breath
- Yo-yo effect
Assess the risks
A “diet without carbohydrates” – that sounds not only extreme, it is too: You put your body in a state of emergency through ketosis and calorie deficit, which actually only brings it to long periods of hunger. This tires him out, which sooner or later will probably also make itself felt mentally.
What’s on the plus side for that? We think: not much. You may lose weight a little faster than with other diets, with water excretion in particular causing the high weight loss at the beginning. You will have those pounds back on as soon as you stop the keto diet. In addition, you will certainly lose some muscle mass – because the more extreme a diet is, the more muscles you lose in the process, after all, muscles are a thankful supplier of replacement energy when carbohydrates are missing.
A disadvantage of ketogenic diets is also the stress that will not be absent if you largely avoid carbohydrates – the fastest and most effective source of energy: the body constantly signals lack of energy and temptations lurk everywhere. Depending on what kind of type you are, this stress can change your hormonal milieu to such an extent that you only slowly or not at all lose weight or even gain weight. Sleep and concentration disorders can also occur.
And with that, the possible problems are not ticked off: Avoiding carbohydrates also means: Less fiber, which increases the chances of constipation. To do this, the ketone body acetone is excreted through the breath, in other words: Bad breath is also to be expected.
Finally, the risk of a yo-yo effect is also very high, among other things because the ketogenic diet differs very far from the average diet in this country. Returning to a “normal” diet is likely to put your weight back up quickly. If, on the other hand, you stick to a ketogenic diet permanently and thus avoid the yo-yo effect, you may increase the risk of serious health problems.
Who can do a ketogenic diet?
Because of the many unanswered questions about the health risks, we think that a ketogenic diet is only something for perfectly healthy, psychologically very resilient people with a very good body image and a lot of basic knowledge about nutrition.
Because you don’t just have to stick to this diet and feel whether it is good for you or not; you also need to know how to get enough vitamins, minerals and fiber despite the restrictions. In addition, you need to know how to continue to eat properly after the diet in order to avoid a yo-yo effect.
Alternatives: Ketogenic Diet?
You can still benefit from a low-carb diet without ketosis. Aim for a daily calorie deficit of 500 kcal and a daily amount of carbohydrates of 100 to 150 g. Make sure that these carbs come with as much fiber (see the “Slow Carb” concept) as possible. In addition, eat 1 to 1.5 g of protein per kg of body weight. The rest of the calories come from fats.
With a diet put together in this way, you can largely bypass the short-term disadvantages of a ketogenic diet and still keep your blood sugar level low. If you want to eat a high-fat diet over the long term and not just on a temporary diet, talk to a doctor about it. He can tell you whether such a diet is suitable for you and what to look out for with regard to fats.