Everything there is to know about the keto diet (concept, benefits and drawbacks)!

What is the concept behind the ketogenic diet?

The British Nutrition Foundation recommends that energy intake for an adult should consist in, depending on age and gender:

• 10 to 20% from proteins,
• 30 to 35% from lipids (fats),
• and 40 to 55% from carbohydrates (sugars, starches)

However, the ketogenic diet, also known as "keto", is based on a drastic reduction in carbohydrate intake (only 50 grams per day, or. 2%) in favour of a fat intake of 90%. Protein intakes, on the other hand, must be limited to 8%.

The ketogenic diet therefore consists of very heavily favouring fats in the diet. We know that the body produces energy mainly via carbohydrates, then via fats and finally via proteins.

So, when carbohydrates are present in very small quantities in the body, the liver starts to produce "ketone bodies" from dietary fat or from the body's fat reserves. The body is then said to be in "ketosis". It becomes a fat burning machine. This is the same idea as when we fast (the body draws its energy from the fats present in the body).

The ketogenic diet involves major changes in eating habits and must, therefore, be followed very strictly in order reach the state of ketone bodies production and thus be effective.

Does the keto diet make you lose weight?

The body usually gets its energy from the carbohydrates consumed during the day. In a ketogenic diet, with carbohydrates almost being completely eliminated, the body starts to draw on its carbohydrate reserves stored in the muscles and liver (called "glycogen stores"). As each gram of glycogen is bound to 3-4 grams of water in the body, weight loss at the beginning of the ketogenic diet is largely related to water loss. 

Thus, when glycogen stores are depleted, the body begins to use fat to produce energy. It then produces waste products called, as mentioned above, "ketone bodies". The ketone bodies then begin to accumulate in the blood and their odour (which is similar to that of nail varnish) becomes noticeable on the breath. This indicator shows that the body is in "ketosis". It takes about two to four weeks to reach the state of ketosis.

This state of ketosis causes a pronounced decrease in appetite, thus reducing the amount of food consumed. The ketogenic diet is not based on calorie counting, but those who follow it do in fact ingest far fewer calories, leading to weight loss. According to Professor Luc Cynober, Professor of Nutrition at the University of Paris School of Pharmacy: "A drastic diet of this type certainly leads to weight loss. The individual can lose several kilos in a month. But the problem with these extreme diets is that there is a rebound effect. People often gain back more weight than they lost at the start". This is the infamous "yo-yo effect".

Which foods are allowed and which are forbidden on the keto diet?

Foods which are allowed in any quantity are:

• Meat
• Poultry
• Fish
• Seafood
• Eggs
• Vegetable oils
• Butter
• Vinegar
• Lemon juice
• Avocado
• Olives
• Vegetables low in carbohydrates (spinach, lettuce, kale, cauliflower, cucumber, courgette, etc.)
• Hard cheeses (100g per day)

Foods which are allowed but in moderation are:

• Whole milk
• Whole milk yoghurts
• Vegetables richer in carbohydrates (except carrots, beets, sweet potatoes, peas and corn)
• Coffee, without sugar

Foods, which keep the body from going into ketosis and are therefore forbidden, are:

• Sugar
• Sweetened goods
• Starchy foods
• Cereals
• Bread
• Pastries
• Cakes and baked goods
• Biscuits
• Fruits (except red berries)
• Potatoes
• Legumes (beans, lentils, chickpeas, peanuts, etc.)
• Sweet vegetables (corn, carrots, sweet potatoes, beetroot, etc.)
• Soft cheeses
• Honey and jams
• Chocolate
• Plant-based milks or yoghurts
• Flavoured yoghurts
• Sweet fruit compotes or purées
• Soft drinks
• Fruit and/or vegetable juices

What are the benefits of the keto diet for chronic illness?

For some chronic conditions, a major dietary change can play a role in improving the patient's state of health. The ketogenic diet has been found to improve the daily life of patients with epilepsy and is also of interest to patients with type 2 diabetes.

The keto diet and epilepsy:

This diet is prescribed for cases of drug-resistant epilepsy (also called refractory epilepsy). It was recognised as early as 1920 as a therapeutic means of treating severe epilepsy in children and adolescents. However, the diet was set aside until the 1990s due to advances in medicine and treatment methods. The keto diet is again being used in refractory epilepsy and/or in more common forms to reduce treatment doses. Studies have found that the diet can reduce seizures by 30 to 40%.

The keto diet and type 2 diabetes:

According to an American study published in the journal Diabetes Therapy, this diet would be beneficial for patients with type 2 diabetes. The study was carried out on 349 people with type 2 diabetes. 87 people received regular care by their dieticians and 262 people followed the ketogenic diet. One year after the start of the study, 83% of the patients who had adopted the ketogenic diet were still following it. On average, each patient had lost 12% of their weight over the course of the year. In addition, 94% of the patients on insulin were able to reduce the dosage or discontinue their treatment and 60% of them had haemoglobin A1C (a marker of diabetes) levels below the diabetic threshold.  

Can the ketogenic diet pose a risk to one's health?

In the majority of cases, the ketogenic diet can cause digestive problems: diarrhoea (linked to the high fat intake) or constipation (linked to the low fibre intake), nausea or vomiting. As a result, many people quickly abandon this diet despite its positive effects.  

The effectiveness of this diet has been demonstrated in the treatment of epilepsy and is of interest in weight loss as well as for patients with type 2 diabetes. However, it is difficult to keep up with because it greatly disrupts eating habits by excluding many everyday foods.

Moreover, the long-term effects of the ketogenic diet are unknown. Vitamin and mineral deficiencies and the risk of heart or metabolic disorders can be induced by a long-term unbalanced diet.

A state of continuous metabolic acidosis also leads to demineralisation and a risk of dehydration. Finally, high levels of ketone bodies can lead to kidney failure or even cerebral oedema (fluid build-up in the brain). The physiological response to this type of diet differs from one individual to another. Some are more sensitive to a high sugar/fat ratio, while others (for example, individuals with a high level of insulin resistance) do well on a low carbohydrate diet.

It is therefore advisable to seek the advice of your doctor before embarking on such a diet.

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