The ketogenic diet – Effective for weight loss?

The ketogenic diet is a diet rich in lipids that has been very fashionable for several years. However, it has been used for almost a hundred years to treat certain pathologies, including epilepsy. This diet aims to significantly reduce the consumption of carbohydrates in favor of lipids to cause ketosis. In addition to significant weight loss, it will have many health benefits.

Features of the ketogenic diet:

  • Very high lipid intake (75% of recruitment)

  • Unchanged protein intake

  • Significant reduction in carbohydrate intake

  • Causes unpleasant symptoms for the first few weeks (ketogenic flu)

  • Rapid weight loss

  • The state of ketosis will have many health benefits (boosting energy, protecting against certain pathologies, etc.)

The main principles of nutrition

Originally used in children with epilepsy to reduce seizures, the ketogenic diet or Keto was developed in the 1920s. This diet showed for the first time antispasmodic effects on epilepsy. Since then, keto diet has gained popularity in recent years as a quick method for weight loss. It is also used to improve the symptoms of type 2 diabetes and cardiovascular disease.

How does the ketogenic diet work?

The ketogenic diet for weight loss is characterized by consumption:

  • 50 g of maximum carbohydrates per day. This represents about 5% of the total calories consumed during the day. A normal diet usually provides between 45 and 65% of our calories in the form of carbohydrates.

  • 75% fat

  • 20% protein

Therefore, this diet completely reverses our traditional food pyramid and its basic principles.

How does a ketogenic diet cause weight loss?

Usually, the body gets its energy from the carbohydrates consumed during the day and which are necessary for the proper functioning of the body. In the ketogenic diet, carbohydrates are extremely limited, the body begins to draw from the carbohydrate reserves stored in the muscles and the liver called “glycogen” reserves. Since every gram of glycogen is associated with 3-4 g of water in the body, significant weight loss at the start of the ketogenic diet is largely water loss. When glycogen stores are depleted, the body naturally begins to use lipids or fats to produce energy. When the body uses lipids in the absence of carbohydrates, it produces waste products called ketones. Then, the ketones begin to accumulate in the blood and their smell, similar to that of nail polish, is felt in the breath. This is the main indicator that the body is in a state of “ketosis”. It usually takes 2 to 4 weeks to reach this state. You can check for ketosis by buying urine measuring tapes from pharmacies.

This state of “ketosis” causes a significant reduction in appetite which contributes to the reduction of food consumption. This condition can also lead to nausea and fatigue. Although this diet does not focus on calculating calories, those who follow it absorb fewer calories because they are not hungry and this results in weight loss.

How long does the ketogenic diet last?

The special ketogenic diet for weight loss does not have a limited duration. it is more of a lifestyle than a diet. When exercised in the therapeutic field, the ketogenic diet has a variable duration from a few weeks to several years depending on the expected results.

Foods are allowed in the ketogenic diet

Foods that are allowed in large quantities in the ketogenic diet are:

  • Fish

  • Seafood

  • Meat

  • Poultry

  • Eggs

  • Butter

  • Vegetable oils

  • Vinegar

  • Lemon juice

  • Olives

  • Avocado

  • Low carb vegetables (spinach, lettuce, cabbage, etc.)

  • Hard cheese (100 g per day)

Approved foods, but for consumption in moderation, are:

  • Whole milk

  • Whole milk yogurts

  • Carbohydrate-rich vegetables (except carrots, beets, sweet potatoes, peas and corn)

  • Wine

  • Strong alcohol

  • Sugar-free coffee

Since a large amount of fat is consumed every day, it is important to worry about the type of fat being consumed. It is recommended to limit the consumption of omega-6 fatty acids which in excess have a pre-inflammatory effect. The main sources of omega-6 are soy, corn, yolk, grape seeds, sunflower oil and wheat germ oil. It is therefore essential to limit the consumption of salad dressings, dressings and mayonnaise with these oils.

It is recommended to consume monounsaturated fats (olive oil, avocados, nuts) and saturated fats (pieces of fatty meat, dairy products high in fat). It is recommended to use coconut oil because it contains fats that are easily converted into ketones. Finally, the consumption of omega-3s contained in fatty fish, oilseed rape and flaxseed, nuts or even chia, flax or hemp seeds should be sufficient.

Prohibited foods

The ketogenic diet is relatively restrictive, many foods are banned there because they prevent the body from maintaining the state of ketosis:

  • Sugar

  • Sweet products

  • Cereals

  • Starch

  • Bread

  • Flour preparations

  • Flour preparations

  • Cookies

  • Legumes

  • Fruits (except berries)

  • Potato

  • Sweet vegetables (beets, corn, carrots, etc.)

  • Cream cheese

  • fresh cheese

  • Soft drinks

  • Chocolate

  • Honey, jams, syrup

  • Fruit and vegetable juices

  • Sweet sauces

  • Milk or yogurt based on vegetable milks (soy, almonds, etc.)

  • Flavored yogurts

  • Sweet fruit compote

What to eat in the ketogenic diet? Typical day menu


Omelette with 2 eggs and a cup of spinach and mushrooms
100 g rhubarb compote

At noon

Beef (150 g)
Green salad (100g) and grated red cabbage (50g)
5 black olives
Vinaigrette (2 to 3 tablespoons)
Snacks: cucumber (50g) and juniper (40g)

The evening

Salmon (200 g)
Asparagus (100g)
Green salad (50g)
Vinaigrette (1 to 2 tablespoons)
1/2 avocado
Hard cheese (40g)


1/4 cup almonds

Advantages and disadvantages

The positive points of the ketogenic diet

  • Feeling full

  • No calorie restriction

  • Good intake of lipids and quality proteins

  • Rapid weight loss

  • Potentially positive effect on blood lipid levels

The negatives of the keto diet

  • Unpleasant side effects for the first few weeks (ketogenic flu)

  • Small nutritional variety

  • No gap is allowed

  • Hard to follow

  • Monotonous

  • It is not compatible with a complete social life

Recommendations and precautions

What are the risks of a ketogenic diet?

In the first few weeks, very unpleasant effects can occur. We are talking about ketogenic flu. It is a transitional period that almost always accompanies the passage of the body in a state of ketosis. Keep in mind that some side effects appear to persist even after the transition period, such as hypoglycaemia (low blood sugar), dehydration and an increased risk of urine or kidney stones and constipation. A fiber and vitamin supplement is recommended when one wants to follow this diet, possibly due to the low content of fruits, legumes and whole grain cereals that are very good sources of fiber and small nutrients.

Cancer, epilepsy: what are the therapeutic indications for the ketogenic diet?

In addition to weight loss, the ketogenic diet is used to treat various pathologies: epilepsy, cancer, inflammatory diseases, etc. That is why it was created in the early 1920s. In the therapeutic world, the value of ketogenic food is no longer proven.

Is a diet compatible with bodybuilding and sports?

Yes, absolutely. Some studies even show the benefits of a ketogenic diet that would allow for better performance, reduce recovery time and make the effort easier. For several years, this diet was very popular in the sports world.

How not to gain weight?

Ketogenic diet is a way of life more than a diet of limited duration. Therefore, it should not be abandoned after a few months. However, given the very large restrictions it creates, it seems inevitable that the weight would increase if it were to stop. To avoid the excessive effect of yo-yo, it would be beneficial to be accompanied by a dietitian who could help with the gradual reintroduction of carbohydrates into the diet without very serious consequences.

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Since the ketogenic diet is very high in fat, there are still many concerns about its potential negative impact on cardiovascular risk. However, according to a recent study conducted in 2013, the ketogenic diet not only leads to greater weight loss than a low-fat diet, but also has a positive effect on blood pressure, HDL cholesterol levels (good cholesterol) and blood triglycerides. The ketogenic diet has also been shown to increase LDL (bad) cholesterol levels. Indeed, saturated fats would not be as bad as you think. This new data remains recent but needs to be taken into account.

In terms of weight loss, the ketogenic diet has been shown to be more effective than a low-fat diet. Indeed, many studies have compared low-fat or high-protein diets and moderately high-carbohydrate diets to the ketogenic diet. The results show that in the short term (1 year and less), the ketogenic diet is more effective in weight loss. However, very few studies have evaluated the effects of this diet in the long run.

The dietitian’s opinion on the ketogenic diet

This diet does not fully respect the basic rules of a balanced diet. It excludes many food groups and seems to forget the meaning of pleasure. Withdrawal of cereals, legumes and fruits can lead to certain deficiencies, especially in fiber, vitamins and antioxidants that play a major role in health. However, it is difficult to deny the positive effects that this diet seems to have on health. Although it is difficult to suggest at this time due to its very limited nature, many ongoing studies should allow us to see a little clearer in the coming years.

Writing: Léa Zubiria, Dietitian-Nutritionist,

June 2018

Based on the project: Audrey Cyr, Nutritionist.

October 2014


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The ketogenic diet – Effective for weight loss?
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