In recent years, the keto diet has become the miracle solution for rapid and lasting weight loss. It is time to take stock of the situation, as one can read everything and its opposite, and often anything. In order to provide complete and objective information, this post will successively address the following questions:
Keto, what does that mean?
Benefits of the ketogenic diet
What are the risks of the keto diet?
What are the recommended and forbidden foods for the ketogenic diet?
Do you need food supplements when following a keto diet?
In short, what should we think of the keto diet?
Keto and intermittent fasting: what are the similarities and differences?
Further information: How does ketosis work in detail?
Keto, qu’est-ce que ça veut dire ?
The ketogenic diet is a diet very low in carbohydrates (in simple terms: sugars, 5%), very high in lipids (fats, 75%) and with a normal to low protein content (around 20%).
A normal diet would consist of 45-40% carbohydrates, 25-30% fat and 30% protein. Of course, there may be significant variations depending on specific needs related to age, physical activity and state of health.
The proportions of a ketogenic diet are therefore extreme: 75% fat instead of 25%, and 5% carbohydrates instead of 45%. The aim is to (violently) deprive your body of carbohydrates, in order to force it to urgently transform the fat reserves in the fat cells into energy that can be assimilated by the body, and thus eliminate them. This stressful situation for the body is called ketosis (hence the name of the diet, "keto"). After a few days in these deficient conditions, the body (for the full chemical explanation, read below) rapidly consumes the glucose reserve (our basic energy reserve) in the liver and red muscles. The liver then metabolises the fat stored in the adipose tissue for energy and produces ketones (a kind of residue of this transformation): you are in a state of ketosis.
This kind of diet seems to have short-term benefits, but also carries many risks.
Les avantages du keto, le régime cétogène
The ketogenic diet, with its very low carbohydrate content, causes the body to consume stored fat, even though the diet itself is very high in fat. This results in a fairly rapid weight loss. Some top sportsmen and women who need endurance or to reduce their weight (mountain bikers, long-distance runners) practice this type of diet, under close supervision of course.
Adherents of this type of diet report increased intellectual alertness linked to this new efficient supply of energy to the brain, the most energy-consuming organ. An American study (https://pubmed.ncbi.nlm.nih.gov/27528626/) reports statistically higher intellectual activity in laboratory rats (for those who can already be convinced by this kind of argument). Other studies (not cited here) identify greater intellectual activity during the first weeks of the keto diet.
A very low carbohydrate diet does not stimulate the creation of insulin or the pancreas. This may be beneficial for some people, depending on their disease situation.
Finally, a diet that suppresses the appetite... Indeed, when the body has access to fat stored in the cells, this high-yield energy source provides a feeling of satiety, which makes the diet much easier to bear.
Quels sont les risques du keto, ou régime cétogène ?
It was too good! The ketogenic diet does have its risks and requires close medical supervision. Even though many websites and online shops praise this diet by offering you adapted products, or even expensive miracle pills, you should not ignore the risks linked to this diet and the consequences on your body. Let's take stock of what is known to date.
Ketones in the blood are partly eliminated by breathing, which causes bitter breath.
The diet must be followed very strictly. Indeed, as soon as you consume even a small amount of carbohydrates, the body quickly switches back to normal glucose consumption. The body will have to be forced back into ketosis mode, with the inconveniences of this transition: feeling tired, irritable, possibly dizzy and sleep disturbed.
Increased mental alertness, for everyone? Ketones are much more quickly absorbed by the brain than glucose, and the brain does not have the capacity to store energy reserves. Reliable scientific studies are still rare and all recent. On the contrary, some testimonies describe a sensation of "foggy brain", indicating that the impression of intellectual agility reported by some is not generalized.
The rapid weight loss is primarily due to two unwanted effects: the almost immediate consumption of glucose reserves leads to weight loss, which is all the more pronounced because for every 1g of glycogen eliminated (glycogen is the form of glucose stored in the body, see below), between 3 and 4g of water are also eliminated. Moreover, after having used up its glucose reserves, the body also draws on its protein reserves: in other words, this diet also melts the muscles at the beginning. When we say that you have to be careful...
Well, the list of possible complications is still long. For example, ketones acidify the blood. To maintain its pH at a normal level, the body seeks to add basic compounds to the blood and one of the sources is the calcium in the bones... Combined with a higher dehydration of the body (induced among other things by a more frequent urge to urinate to eliminate toxins), this also increases the risk of kidney problems like kidney stones. The relative lack of fibre in this diet also often leads to constipation. Bad luck when you want to lose weight!
Note, however, that some populations have naturally always been on ketogenic diets because of the foods available in their traditional natural environment. Examples include the Inuit and the Maasai. But this is a way of life rather than a diet, and the body has become accustomed to it over many generations.
Quels sont les aliments recommandés et les aliments proscrits pour le régime cétogène ?
As you can see, this diet bans carbohydrates and replaces them with fats. In addition, it is important to vary the sources of fats to ensure a sufficiently balanced diet. Foods that conform to the ketogenic diet include:
meat, including poultry
fish
shellfish
eggs
butter
all vegetable oils
vinegar, lemon juice
olives and avocado
hard cheeses
low-carbohydrate vegetables (especially leafy vegetables such as lettuce, spinach, etc.)
Coconut oil is special in that the body rapidly converts it into ketones. In particular, MCT oil (for Medium Chain Triglycerides, the C8 and C10) is derived from coconut oil from which only the C8 and C10 fatty acids have been kept. It is easily assimilated by the body and therefore effective in providing energy in a keto diet. With the longer chains removed, it is liquid at room temperature and therefore easier to incorporate into culinary preparations.
But the most important thing is to vary the oils: vegetable oils are often not very varied in fatty acids, and our body "needs a bit of everything".
In addition, many foods are forbidden in this diet because of their carbohydrate content:
sugars of course, and sweetened products, chocolate, flavoured yoghurts, vegetable drinks, sweetened fruit compotes (and sugar), honey and jams
cereals, starches, pulses, potatoes, sweet vegetables (beetroot, corn, carrots, etc.)
fruit, fruit and vegetable juices, hard liquor, soft drinks
bread, pastries, biscuits
soft cheeses.
Faut-il des compléments alimentaires quand on suit un régime keto?
The selectivity of foods imposed in the diet implies a much lower intake of fibre, vitamins and minerals. The long-term ketogenic diet can therefore lead to serious deficiencies with harmful consequences for the body. Hence the real interest of medical follow-up. There is an almost infinite number of online sales sites that offer a range of food supplements adapted to ketogenic diets. In fact, they have the answer to every type of diet possible and imaginable. The advice to give is very simple: absolute caution...
The ketogenic diet is the subject of several medical studies in the fight against a range of brain diseases, due to positive indications observed in specific situations. As cancer cells are high consumers of glucose, ketosis is also being studied in the fight against cancer. There are still no comprehensive studies on the long-term consequences of the ketogenic diet.
En bref, que faut-il penser du régime keto ?
As we can see, the ketogenic diet imposes a particular way of functioning on the human body. It is the subject of numerous medical studies because it has a number of virtues. But it also involves serious risks and requires professional supervision to avoid any harmful side effects.
The ketogenic diet certainly provides answers to a range of pathologies. As far as we are concerned, it is also a remarkable fad supported by great marketing efforts of often unscrupulous brands to sell a series of expensive products that are not needed. Let's hear it...
Keto et le jeûne intermittent
Intermittent fasting consists of following a strict eating schedule and not eating for 16 hours in a row each day (there are variations on the number of hours, but 16 hours is a minimum). It also advises limiting carbohydrate intake, but there is no mention of the huge imbalance of the keto diet. Instead, the emphasis is on a balanced diet containing fruit and vegetables, fats, carbohydrates and proteins. Like keto, intermittent fasting does not advocate a reduced calorie intake in line with normal daily requirements. The 16-hour period is long enough, provided that the person eats a normal amount of food during the permitted period, for the body to briefly deplete its glucose reserves. The body then goes into a brief state of ketosis and metabolises the fat in the fat cells. The resulting feeling of hunger provides a sense of mental alertness that some people enjoy. However, the brief state of ketosis has nothing to do with the prolonged state obtained with the ketogenic diet. Here too, scientific studies are still scarce. A recent American study reports a statistical effect on weight loss, but does not demonstrate a greater effect than other weight loss diets, nor does it analyse the possible health consequences (https://www.sciencedaily.com/releases/2018/06/180618113038.htm).
However, it is clear that intermittent fasting is much less risky than the ketogenic diet, with a number of advantages.
Given the importance of the subject and its popularity, we are preparing a full and detailed post on this method of eating, also closer to a lifestyle, to highlight all its benefits. Stay tuned!
Pour aller plus loin : comment la cétose fonctionne-t-elle en détail ?
Let's go back to the diet prescriptions: 75% fat instead of 25%, and 5% carbohydrates instead of 45%. To understand the value of these proportions, let's see what these nutrients are used for.
Carbohydrates, composed of carbon, hydrogen and oxygen (which is why they are also called carbohydrates), are the most rapidly available source of energy for the body (1g of carbohydrates gives about 4 kcal). They are very useful for the muscles and the brain and for protein anabolism (i.e. they help to build muscle from protein). In simple terms, carbohydrates are the body's usual fuel. Carbohydrates are broken down into glucose, which is distributed throughout the body for consumption (in practice: consumed inside the cells, in the mitochondria). Some of this glucose is stored in the muscles and liver as glycogen. This is the first energy reserve used by the body during muscular effort. We will talk about simple and complex carbohydrates, as well as the glycemic index, in another post.
In a balanced diet, the carbohydrate intake should be in the range of 40-50%. An athlete will need at least 55%, and children and infants also need more. An average person (70 kg) would therefore need about 220 to 250 g of carbohydrates per day. Two thirds of this can be used by the nervous system, which is a major consumer of carbohydrates.
Carbohydrates are of plant origin. Carbohydrates are mainly found in dried fruit, cereals, including wholemeal bread (50%), pasta (75%), dried vegetables (60%), tubers (20% for potatoes), honey of course, rice (20%)...
Lipids, the name given to fats of animal or vegetable origin, are also essential to our body. They are the most energy-rich nutrients: 1g gives 9 kcal. Certain lipids (the so-called "complex" lipids) are the essential constituents of biological membranes (at the cellular level). With varying permeability, they regulate intra-cellular exchanges. Lipids are not soluble in water but only in organic solvents.
Most (over 95%) edible fats are "triglycerides". In simple terms, these are 3 pieces of fatty acids attached to a glycerol (another name for glycerin) molecule. These triglycerides can be saturated, monounsaturated or polyunsaturated. These are terms you often hear in advertisements for diet margarines...
Triglycerides play a fundamental role as an energy reserve (fatty acids provide energy, glycerol allows storage). It is considered that 10% of a normal person's weight is made up of triglycerides. By way of illustration, it would take 6 times more glycogen (see above) to store the same amount of energy. Triglycerides are stored in the body's fat cells. This energy is available much more slowly than glycogen, however.
Vegetable oils are made up of 100% lipids, but not always the same lipids of course. Animal fats have varying proportions of lipids. It should be noted that oils should be varied in the diet to ensure a balanced intake, particularly of "essential fatty acids", which are both essential for our body and impossible for it to synthesise: linoleic acid and alpha-linoleic acid (for those who like to read the compositions of the products they eat).
Excessive fat intake leads to weight gain: WHO recommends no more than 30% of total energy intake in a non-high calorie diet ( https://www.who.int/fr/news-room/fact-sheets/detail/healthy-diet; Hooper L, Abdelhamid A, Bunn D, Brown T, Summerbell CD, Skeaff CM. Effects of total fat intake on body weight. Cochrane Database Syst Rev. 2015; (8):CD011834).
The aim of the ketogenic diet is literally to wean the body off carbohydrates. The body will quickly exhaust its glycogen reserves. The liver will then metabolise the triglycerides and produce ketones. These ketones are transported in the blood and constitute the new fuel for the cells. In the brain (and the entire nervous system), ketones are converted into energy more quickly than glucose, which gives a feeling of greater intellectual agility, attention and concentration. As seen above, this nevertheless causes a series of other imbalances in the chain that the body tries to compensate for in one way or another. As fat has a greater calorific capacity (ability to release energy), the feeling of satiety is greater.
Here is an overview of the keto diet. As usual, this is a personal choice, easier to make when properly informed. We are not specialists, our information is taken from articles from the scientific community, which ensures its reliability, based on the current state of knowledge. We are convinced that popularising this information without truncating or altering it and making it accessible to all is fundamental to help us make "good" choices, in full knowledge of the facts. Knowledge and understanding are two weapons to resist the sirens of marketing and commerce, which do not always aim to improve our well-being or preserve our planet.
We will continue to monitor this and other issues and keep you informed as soon as new data becomes available.
See you soon for more information to help us make the right choices.