Can the ketogenic diet really help you lose weight?

Losing weight while eating fat: this is the surprising promise of the ketogenic diet, to say the least. Used for nearly a century against certain forms of epilepsy, the ketogenic diet has gradually found a place alongside weight-loss diets. 

Can the ketogenic diet really help you lose weight
Diet Keto Foods

For some time now it has had some success, as evidenced by the twenty or so books published in recent years and the numerous press articles which are frequently devoted to it. How does this diet work? What do we know about its effectiveness? Le Figaro takes stock. 

What is the ketogenic diet?

The National Food Safety Agency (ANSES) considers that, for an adult, about 10 to 20% of energy 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 carbohydrate intake (no more than 50 grams per day for an adult) in favor of a massive intake of lipids (70 to 90% of total energy intake), with a protein intake that remains at 15-20% of intake. Rather counterintuitive, in a world where fat plays a bad role in the collective imagination.

Foods made from cereals (bread, pasta, rice), potatoes, prepared meals, sweets, cakes, and milk (rich in lactose, which is a carbohydrate) should be prohibited. Certain fruits and vegetables, too rich in carbohydrates (a banana provides about 30 grams of carbohydrate out of the 50 required), are also to be avoided, as well as legumes. On the other hand, you should bet on all foods rich in fat and protein such as vegetable oils, butter, eggs, meats, oily fish, avocado, coconut, or even oilseeds (almonds, Hazelnut...). "In practice, it's 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, Don't take risks! (Ed. Michel Lafon).

How it works?

To function, the body has three types of food fuels: carbohydrates, fats, and proteins. When carbohydrates are very low - as is the case with the ketogenic diet - the liver begins to make ketones from dietary fat or the body's fat stores. It is said that the body is in "ketosis": it turns into a machine to "burn" fat. Ketone bodies, therefore, become the main source of energy for most of our cells. This change occurs on average between two and four days after adopting the diet.

Can the ketogenic diet help you lose weight?

"A drastic diet of this type definitely makes you lose weight," says Professor Cynober. “An individual can lose several pounds in a month. But the problem with these extreme diets is that there is a rebound effect. Oftentimes people gain more weight than they initially lost. " The famous "yo-yo" effect, which is found in all diets.

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

According to the doctor, we must distinguish this diet - where carbohydrates are almost eliminated - from low-sugar diets. "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," he says. But we must be extremely careful with the type of fats consumed and favor those of plant rather than animal origin, otherwise, there is a risk of developing fatty liver (hepatic steatosis) and hypercholesterolemia, with harmful effects in the long term. "

For now, even if the promises of the ketogenic diet are spreading (weight loss, but also cancer, Alzheimer's disease, etc.), it should be remembered that its effectiveness has only been scientifically proven in epilepsy.

Are there any side effects?

In the short term, switching from a traditional diet to a ketogenic diet can lead to nausea, constipation, fatigue, headaches, cramps, bad breath ... All these inconveniences mainly related to dehydration. "With this diet, the body is forced to use its glucose stores," explains Prof. Luc Cynober. “But in muscle glucose is stored with water. Its use, therefore, results in the elimination of water which contributes to weight loss but also to dehydration ".

This diet, which involves reducing the consumption of fruits and vegetables, can also lead to deficiencies. "There may be a deficit in vitamins, minerals, and fibers", abounds Professor Cynober. Hence the need to seek advice from a dietitian or a nutritionist before embarking on such a business.

In the long term, the consequences are poorly understood. Most of the scientific work done so far has focused on a small number of participants and/or does not include a control group for comparison. "The strongest data we have come from children with epilepsy," says Dr. Jornayvaz. "They show that there is a risk of developing kidney stones, osteoporosis and growth disorders over time."

Finally, I will leave you with this reflection "Man is programmed for balanced and omnivorous diets", recalls Professor Cynober. "Needless to say, stuffing the body with fat by completely cutting out carbohydrates is probably not good for your health."

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