Can a keto diet really help you lose weight?

OUR HEALTH ADVICE - Lose weight by eating fat without sugar: this is to say the least, the shocking promise of the ketogenic diet. How is it working? Is this efficient? We're taking stock.

Losing weight when eating fat: this is the ketogenic diet's shocking promise, to say the least. Used against some types of epilepsy for almost a century, the ketogenic diet has steadily provided a position for itself alongside diets for weight loss. It has had some popularity for some time now, as shown by the twenty or so books published in recent years and the numerous press articles that are often dedicated to it. How's this diet working? What do we know about the efficacy of it?

What does a ketogenic diet mean?

The National Food Safety Agency (ANSES) claims that about 10-20% of energy for an adult must come from proteins, 35-35% from lipids (fats) and 40-55% from carbohydrates (sugars). The ketogenic diet is based on a drastic reduction in the consumption of carbohydrates (no more than 50 grams per day for an adult) in favor of a massive lipid intake (70 to 90 percent of the total energy intake), with a protein intake of 15-20 percent of the intake remaining. Very counter-intuitive, in a world where in the collective imagination, fat plays a bad part.

It is important to avoid food made from cereals (bread, pasta, rice), potatoes, cooked meals, candy, cakes and milk (rich in lactose, which is a carbohydrate). It is also important to avoid some fruits and vegetables that are too rich in carbohydrates (a banana provides around 30 grams of carbohydrates out of the 50 required), as well as legumes. On the other side, you can bet on all fat and protein-rich foods, such as vegetable oils, butter, eggs, beef, fatty fish, avocado, coconut, or even oily seeds (almonds, Hazelnut...). "In practice, it is a very difficult diet to follow",notes Prof. Luc Cynober, head of the biochemistry department at Cochin hospital (AP-HP) and author of Tout sur votre Weight, Do not take risks! (Ed. Michel Lafon).

How does it function?

The body has three types of dietary fuels in order to function: carbohydrates, fats and proteins. The liver starts to produce ketones from dietary fat or the fat reserves of the body when carbohydrates are very minimal - which is the case with the ketogenic diet. The body is said to be in "ketosis": it transforms into a fat "burn" engine. As a consequence, ketone bodies are the primary source of energy for most of our cells. On average, this transition happens between two and four days after the diet is implemented.

Will your weight loss be improved by a ketogenic diet?

Professor Cynober says, "A drastic diet of this type definitely makes you lose weight," "In a month, a person can lose many pounds. But the issue with these strict diets is that a rebound effect occurs. "People often gain more weight than they originally lost ". The popular effect of "yo-yo" which is present in all diets.

Research has shown that diets low in sugar allow you to lose weight faster than diets low in fat. But the weight curves come together in the long-term, ”says Dr François Jornayvaz, head of the diabetology unit at Geneva University Hospitals and author of several scientific articles on the ketogenic diet.

According to the doctor, it is important to distinguish this diet - where carbohydrates are almost removed - from low-sugar diets. We have reason to believe that, particularly for diabetic patients, moderately low carbohydrate diets that do not exceed 130 grams of sugar per day may be beneficial, “We have reason to believe that moderately low carbohydrate diets, which do not exceed 130 grams of sugars per day could be beneficial especially for diabetic patients," But with the form of fats consumed, we must be extremely cautious and favor those of plant rather than animal origin, Otherwise there is a chance of developing hypercholesterolemia and fatty liver (fatty liver) with long-term adverse effects. "

For the time being, even though the promises of a ketogenic diet are expanded (weight loss, but also cancer, Alzheimer's disease, etc.), it should be noted that only epilepsy has clinically proved its efficacy.

Are there any adverse reactions?

Switching from a conventional diet to a ketogenic diet in the short term will result in nausea, constipation, tiredness, headaches, cramps, bad breath... Many of these disadvantages are mostly related to dehydration. "The body is forced to use its glucose reserves through this diet," Prof. Luc Cynober states. "But glucose is processed in the muscle with water. Therefore its use results in the reduction of water that leads to weight loss but also dehydration.

This diet, which includes reducing fruit and vegetable intake, can also contribute to shortcomings. "There may be a deficit in vitamins, minerals and fibres" Professor Cynober says. Hence before embarking on such an enterprise, the need to take advice from a dietitian or a nutritionist.

The implications are poorly known in the long term. Much of the research work done so far has concentrated on a limited number of participants to allow comparison and/or does not involve a control group. "Dr. Jornayvaz says The best evidence we have came from children with epilepsy. "They show that there is in the long term, a risk of developing kidney stones, osteoporosis and a growth disorder."

The National Food Safety Agency (ANSES) noted in a 2010 study on weight loss diets that the search for weight loss without a formal medical indication carries risks, in particular when unbalanced and poorly diversified diets are called for." In addition, the Agency emphasised that nothing can replace, in terms of health, a balanced, diversified diet, ensuring that the daily energy intake does not exceed the needs."

Professor Cynober recalls, "Man is programmed for balanced and omnivorous diets," "Needless to say, stuffing the body with fat by completely eliminating carbohydrates is probably not good for your health."