Ketogenic nutrition largely dispenses with carbohydrates and energy is provided mainly by the two other macronutrients fat and protein. But what is behind this hype? It is believed that the ketogenic diet (in the following text also called "keto diet“) supports weight loss, inhibits inflammation, improves energy levels and inhibits the growth of cancer cells. The reduced insulin secretion also has a positive influence on stable blood sugar levels and can reduce the risk of type 2 diabetes.
What is the ketogenic diet?
This diet consumes very few carbohydrates. With few exceptions, foods in the ketogenic diet should not have more than 10g of carbohydrates per 100g. Sugar is completely taboo. Exactly which foods belong to this diet and which do not, will be described in more detail below. Mainly cereals, sweets and starchy foods like potatoes are omitted.
No more than 30-40g net carbohydrates should be consumed per day. These result primarily from vegetables or berries. For this, sufficient protein should be consumed and fat serves as the main source of energy. Thus, 75-85% of the daily calorie intake comes from fatty acids1.
What happens in metabolism when we eat carbohydrates?
When we eat carbohydrates, they are broken down in the intestines into monosaccharides, because this is the only way they can be absorbed into the bloodstream. Of course, our intestinal mucosa also absorbs sugars, which can be found in sweets or lemonades, for example. In this liquid form, absorption takes place most quickly, while the slowest absorption occurs with more complex carbohydrates, for example from whole grain rice and vegetables. When the sugar enters the bloodstream, it supplies the cells with energy. The excess sugar is storaged in our muscle and liver cells.The signal for this storage process is given by the hormone insulin. Here you will find more detailed explanations about blood sugar.
However, the carbohydrate or sugar storages in our body are limited and when they are already full, the excess sugar is converted into fat by our liver and storaged in the cells. In contrast to the sugar storages, the fat storages can be expanded almost indefinitely.
How does ketosis occur?
If no or almost no carbohydrates are taken in with food, after a while the body begins to break down the carbohydrate storages from the liver and use them as a source of energy for nerve cells and the brain or for the muscles. The glycogen storages in the muscles are then also slowly emptied. This ensures that there is always a certain level of sugar in the bloodstream in order to guarantee the energy supply3.
However, since these sugar storages are used up without being reabsorbed through food, the liver first begins to convert amino acids (the split form of protein) into carbohydrates3. However, only a third of the amino acids in the body are actually available for this. The rest is needed for other processes. storaged fat, however, is available in eleven times the amount of calories. In people with a higher body fat percentage, these storages are even higher.
So it only makes sense that the body now uses these fatty acids as carbohydrate substitutes.
With the ketosis now occurring, the liver converts the fats into so-called ketones or ketone bodies. Although they cannot be transformed into the sugar that is actually needed, they perform the same functions in energy metabolism. They are therefore virtually a substitute product for carbohydrates. So our energy system works like a hybrid car: when the electric storage tank is empty, it switches to petrol, our electricity would be the carbohydrates and the petrol would be the ketone bodies4.
This ketogenic state is not dangerous or unhealthy. The process is completely natural and was a survival mechanism in primeval times, because back then there were no filled shelves in the supermarket. At times, people often had hardly any carbohydrates available and simply had to get by without them. It is possible, however, that short-term side effects may occur in the first few days of the changeover:
Headaches, tiredness and the urge to eat sugar are typical signs that the body is in the changeover phase. However, these signs disappear after a few days and are usually due to sugar withdrawal.
- Animal protein: fish, meat, eggs, e.g. salmon, mackerel, tuna, seafood, gilthead, ground beef, boiled meat, chicken, turkey, bresaola, bacon, game, collagen, whey protein, bone stock, gelatine, etc.
- Natural fat: butter, ghee, coconut oil, MCT oil, virgin olive oil, virgin sunflower oil, linseed oil, 100% nut and kernel puree, avocado, etc.
- Grains and nuts (also belong to fats): Sesame seeds, linseeds, chia seeds, walnuts, hazelnuts, pumpkin seeds, sunflower seeds, pecan nuts, almonds, coconut, etc.
- Dairy products: Cheese, yogurt, kefir, butter, milk, cream, sour cream, buttermilk, curd, granular cream cheese etc.
- Low sugar drinks: coffee, Bulletproof Coffee (with butter, MCT oil and collagen), infused water, unsweetened tea, sugar-free amino acids and protein shakes etc.
- Low-carbohydrate vegetables: lettuce, cucumber, spinach, asparagus, courgette, broccoli, cauliflower, green beans, artichoke, eggplant, onion, spring onion, leek, mushrooms, peppers, Brussels sprouts, olives, chilies, etc.
- Fruit with low sugar content: berries, e.g. blueberry, blackberry, raspberry, strawberry, currant, cassis, lemon, lime etc.
- Flour alternatives for cooking and baking: Almond flour, carob gum, linseed flour, coconut flour, walnut flour etc.
- Sugar alternatives/ natural sweeteners: stevia, erythritol, xylitol etc.
Donts: These products and foods are not on the keto diet
Since it is mainly about avoiding carbohydrates, it is important to avoid cereals, sugar, potatoes, sweet drinks, juice, most fruits and also vegetables that are too rich in carbohydrates in the keto diet. The following examples are in no case on the keto diet:
- Grain products: Noodles, rice, bread, wheat, rye, spelt, barley, corn, potato, sweet potato, chips, rice wafers, crackers, muesli, cornflakes, oatmeal, pizza, etc.
- Pulses: chickpeas, peanuts, lentils, beans, soya etc.
- Sugary foods: chocolate, desserts, sweetened dairy products such as fruit yoghurt, jam, maple syrup, honey, household sugar, fructose (agave), coconut blossom nectar, ready-made products containing sugar, pancakes, cakes etc.
- Vegetables with high carbohydrate content: pumpkin, carrot and other tuber vegetables
- Beverages with high sugar content: fruit juices, fruit smoothies, sweet drinks e.g. cola, fanta, sprite, energy drinks etc.
- Fruit with high sugar content: banana, apple, melon, cherry, peach, nectarine, pear, date, mango, apricot, pineapple, orange, tangerine, papaya etc.
Differentiation from the Paleo diet
The last article was about the Paleo diet, which has some parallels to the keto diet: The Paleo diet also consumes few carbohydrates, cereals are taboo and protein and fat are in focus. However, no dairy products are allowed in the Paleo diet, but various sugary fruits, little honey and some starchy foods like sweet potatoes are in a grey area. In the ketogenic diet, some tuber vegetables such as carrots are avoided because they contain more carbohydrates, this is not the case in the Stone Age or prehistoric diet.
What are the advantages of the ketogenic diet?
Primarily it keeps the blood sugar low and stable – which has many healthy and aesthetic benefits:
Less insulin is secreted, allowing the pancreas to recover and reducing the risk of type 2 diabetes. The constant blood sugar level results in fewer ravenous attacks, which means less excess energy is storaged in the fat cells. This makes the keto Diet a way to lose weight without starving or counting calories. The more stable blood sugar also improves energy levels and concentration5.
Because many potential allergens such as gluten and soy are automatically eliminated, the intestinal mucosa can recover. As a result, there is less inflammation in the digestive tract and throughout the body. By doing without sugar, the oral flora and the ratio of microorganisms in the mouth and throat can improve, which prevents caries and other diseases in the oral cavity. There are also numerous studies on the subject of cancer and ketogenic diets that advocate this form of nutrition. Cancer cells feed on sugar, so it is of little benefit if the body has enough or excessive amounts of it.
Caution with ketogenic diets – for whom it's not recommended
Not all keto products are suitable for people who cannot tolerate dairy products. However, this should not be a complete limitation, as there are plenty of other foods that can be consumed. For vegans it could still be a bit more complicated: you should be careful with the ketogenic diet and talk to a doctor about possible micronutrient and essential amino acid supplements.
Athletes with a high muscle content and low body fat are usually advised against ketogenic diets: Their carbohydrate storages are larger than those of an average person and are regularly emptied during intensive training sessions. The provision of energy via ketosis then to take a detour is less sensible. In order to take in enough correct nutrients for muscle building or maintenance, you would have to consume extremely high amounts of animal protein, which could possibly strain the kidneys and is also ecologically and ethically questionable.
Conclusion on the keto Diet:
The ketogenic diet can have many health and body slimming benefits. However, like any diet, it is not optimal for all people and may require some adjustment.
1 DRKS (2017): Einfluss einer energiebilanzierten ketogenen Diät (KD) - einer stark kohlenhydratreduzierten und fettreichen Kostform - auf die körperliche Ausdauerleistungsfähigkeit von gesunden Erwachsenen
2 Simply keto: Was ist die ketogene Ernährung? [https://simplyketo.de/was-ist-keto; 25.07.2020].
3 Martin, Hans Helmut (2014): Volle Energie im Fasten. UGB forum spezial. S 10-14.
4 Bracht, Dr. Med. Petra (2018): Intervallfasten – Für ein langes Leben – schlank und gesund.
5 Medizindoc (2020): Studie: Wie eine ketogene Diät am besten wirkt – Vor- und Nachteile einer ketogenen Ernährung. [https://medizindoc.de/studie-eine-ketogene-diaet-funktioniert-am-besten-in-kleinen-dosen-finden-wissenschaftler-der-yale-university; 26.07.2020].