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

Published 20 Nov 2020 • By Candice Salomé

Recognised in the treatment of drug-resistant epilepsy since the 1920s, the ketogenic diet has become popular in recent years, allowing rapid weight loss. This high-fat, low-carbohydrate diet goes against the usual nutritional recommendations. 

So what does the ketogenic diet really consist of? How can it be implemented in everyday life? What are its benefits for certain chronic illnesses? Is it easy to follow? Does it pose a risk to your health?

We tell you everything in our article!

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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avatar Candice Salomé

Author: Candice Salomé, Health Writer

Candice is a content creator at Carenity and specialises in writing health articles. She has a particular interest in the fields of women's health, well-being and sport. 

Candice holds a master's degree in... >> Learn more


on 21/11/2020

This article is very important I have taken many things on here which I shall take on board and give it a try if I can lose a few inches I will be over the moon hopefully it will help thank you fo this information 

on 21/11/2020

I have absolutely no problems losing weight. Over the past year  thanks to my terminal lung cancer I’ve lost nearly two stone,and no special diet was needed!  But might not work for everybody!.....

on 21/11/2020

I have always had trouble with putting on weight so I can see no advantages in this diet for me. 

on 22/11/2020

I have loads of illnesses and I am fighting breast cancer, as well but my coeliac disease causes bloating of my stomach so I have to be very careful of what I eat now because before I was diagnosed I was completely anorexic, suffered really bad with osteoporosis brittle bones I would only just knock my self and my bones would splinter ,when I was 4 I slipped top to bottom of our stairs and my leg didnt break it split so they had to break it to mend it I wore a boot for many weeks but nobody knew I was a coeliac, so when I was diagnosed at 49 ,I was really I'll close to dying ,I was anorexic, osteoporosis, my teeth were crumbling, and I was suffering with anaemia, 2.5 foliate level and I was having many ear and throat infections, also I was poisoning the lining of my stomach because I was eating all the wrong foods so they diagnosed me as a Coeliac and I was told It should have been diagnosed from birth so everything containing gluten ,wheat,barley ,and oats ,was slowly killing me ,so they put me on a food intolerance diet that doesnt contain any of these ,now I am border line with diabetes, hypertension, angina, osteoporosis, migraines, ear infections which has sent me completely deaf in both ears, , gaul stones,glaucoma,emphysema,  liver disease, now on top i am fighting breast cancer, had a mastectomy and radiotherapy, which has left me with lymphoedema, and on top of all that i have PTSD low moods depression and anxiety, so if i could just lose a  bit of weight i would feel a lot better because now being on the gluten free diet i feel like an oversized whale but at least I'm alive and with this pandemic not being able to go out I'm putting on more weight and my mental health has got worse ,i have been so down just lately ,i can help others with there mental health but not my own ,Tigger 

on 22/11/2020

For me I lose weight by not eating as much, during this lockdown I am home unless taking the wife to and fro work, or with the wife shopping. So I do very little outside exercise, usually climbing the stairs a lot, this is why I eat less. I do like full cream milk, sugar (I cannot use supplements due to their taste, makes me heave), vegetables, rice, cheese, jams and marmalade. I enjoy the food I eat and will not change for any reason, for the climate or whatever. I'd rather enjoy what we have today, as you are here only once. People say diets make you live longer, but the stress and the anxious moments that this life actually gives you, maybe a little shorter lifespan is better in the long run. We all have medical issues, and there has been so many diets over the years, as I said to my medical team, they all come and go, and I have never partaken in any one of them and I am still here as healthy as I was back then (in my eyes). Diets are for those who need them, or wish to try something new, me I pass, PG

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