Ketogenic or Keto Diet: What is it and for whom is being addressed?

Keto diet or ketogenic diet was originally used to treat drug-resistant epilepsy in children, as it appears to reduce the frequency and intensity of seizures. Keto diet became well-known and began to be widely used when people realized it was being used for weight loss.

What foods does a keto diet include?

The foods, included in a keto diet, are those that are high in fat, low in carbohydrates and moderate in protein, such as:

Avocados
Eggs
Fats, including oils such as olive, palm and coconut, as well as butter
Meat and poultry
Cheese
Nuts
Olives
Seeds
Berries in very limited quantities (¼ cup) because they contain carbohydrates, although less than other fruits
Dark chocolate and cocoa powder

What about fruits and vegetables?

All fruits are high in carbohydrates, but some fruits (usually berries) can be eaten in small portions. Vegetables (also high in carbohydrates) are limited to leafy greens (such as cabbage, chard, spinach), cauliflower, broccoli, Brussels sprouts, asparagus, peppers, bell peppers, onions, garlic, mushrooms, cucumber, celery and summer squash.

How does keto diet work?

Keto diet aims to force the body to use a different type of fuel. Instead of relying on sugar (glucose) derived from carbohydrates (such as grains, legumes, vegetables and fruits), keto diet relies on the production of ketone-bodies, a type of fuel that the liver produces from stored fat, through the process of ketosis.

What is ketosis?

Under normal circumstances the body uses glucose from carbohydrates to fuel activity and support basic vital organ functions. When the body is deprived of its main source of energy, it will find an alternative source. The brain requires glucose and when there are insufficient amounts, it draws stored glucose from the liver and muscles.

After 3-4 days, when these stores are depleted, the liver converts the fat into ketones.

Fat burning seems like an ideal way to lose weight. But getting the liver to produce ketone bodies is difficult:

It requires carbohydrate deprivation, less than 20 to 50 grams of carbohydrates per day (consider that a medium-sized banana has about 27 grams of carbohydrates).
It usually takes a few days to reach a state of ketosis.
Eating a lot of protein can affect ketosis.

Does a keto diet work?

Keto diets appear to lead to weight loss and may improve insulin sensitivity in people with diabetes.

Weight loss at the beginning of the diet can be rapid, in some cases up to 4.5 pounds in two weeks. This initial loss is usually due to the diuretic effect of the diet (water is lost as stored muscle glucose is used) and is then followed by fat loss. As ketosis continues, you may feel less hungry and because ketosis is a calorie-consuming process (there is an increased demand for calories to convert fat and protein into ketones) you may experience further fat loss.

A comprehensive review of scientific evidence published in 2019 in the Journal of Clinical Lipidology looked at the effect of low-carbohydrate and very low-carbohydrate diets such as keto on body weight. It found that keto-type diets are no better than other types of diets, such as low-fat diets in bringing about long-term weight loss.

Benefits of ketogenic diet

Less Hunger. There is evidence that keto diets reduce hunger, according to a 2019 review in the Journal of Clinical Lipidology. The effect may be due to a shift in hunger hormones, such as ghrelin and leptin, as well as insulin.
Blood sugar control. Eating fewer carbohydrates may cause the pancreas to secrete less insulin and may lower blood sugar. This response may be helpful for people with prediabetes, insulin resistance or diabetes.
Lower Triglycerides. Κeto diet can cause triglycerides, a type of fat found in the blood, to drop. High triglyceride levels can increase the risk of heart attack and stroke. However, this decrease does not hold up over time. A 2020 review in the journal Cureus found that while the keto diet led to reductions in triglyceride levels, as well as blood pressure, in the first six to 12 months after starting a keto diet, these effects disappeared after 12 months.

Risks of keto diet

High saturated fat content. Saturated fat consumption should not exceed 7% of daily calories due to its association with an increased likelihood of heart disease. And indeed, keto diet is associated with an increase in "bad" LDL cholesterol, which has been also linked to the development of heart disease.
Nutrient deficiency. If you don't eat a wide variety of vegetables, fruits, and grains, you may be at risk for micronutrient deficiencies, such as selenium, magnesium, phosphorus, and vitamins B and C.
Liver problems. With such a high fat intake, the diet could worsen any existing liver conditions.
Constipation. The keto diet is low in high-fiber foods such as grains, legumes and fruits.
Fuzzy thinking and mood swings. The brain needs glucose from carbohydrates to function. Low carbohydrate diets can cause confusion, irritability and headaches.

In conclusion, keto diet should only be planned by health professionals, and in particular by dieticians-nutritionists, for a limited period of time, as it is a difficult dietary pattern to implement. It may benefit people with prediabetes or insulin resistance. However, in the long term, due to the difficulty of adherence and perhaps a lack of certain micronutrients, it would be advisable to make a gradual transition by reintroducing carbohydrates according to the Mediterranean dietary pattern.

Scientific references

Bueno, N., De Melo, I., De Oliveira, S., & Da Rocha Ataide, T. (2013). Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: A meta-analysis of randomised controlled trials. British Journal of Nutrition. 110(7), 1178-1187.

Kirkpatrick CF, et al. (2019). Review of current evidence and clinical recommendations on the effects of low-carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors: A scientific statement from the National Lipid Association Nutrition and Lifestyle Task Force. Journal of Clinical Lipidology. 13:689-711.

Batch JT, Lamsal SP, Adkins M, Sultan S, Ramirez MN. (2020). Advantages and Disadvantages of the Ketogenic Diet: A Review Article. Cureus. 12(8):e9639.

Wheless JH. (2008). History of the ketogenic diet. Epilepsia. (49)3-5.

Ketogenic diet. (2021). Epilepsy Foundation.

Arnett DK, Blumenthal RS, et al. (2019). Guideline on the Primary Prevention of Cardiovascular Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation. 140:e596–e646.

O’Neill B, Raggi P. (2020). The ketogenic diet: Pros and cons. Atherosclerosis.292:119-126.