What is the ketogenic diet or "KETO"?
The ketogenic diet, or "keto diet" in English, is a low-carbohydrate, high-fat eating plan. It has become popular again in recent years as a diet for rapid weight loss, although it has been used to treat certain medical conditions since the 1920s.
In this diet, carbohydrates account for about 5% to 10% of the daily energy intake, which is between 20 and 50 g of carbohydrates. As for fat intake, it represents between 45% and 75% of the daily energy consumed. For comparison, in a balanced diet, carbohydrates generally make up between 45% and 65% of the daily energy intake, and fats between 20% and 35%.
However, carbohydrates are the main source of energy for certain organs, especially the brain. Indeed, it is often recommended to consume a minimum of 130 g of carbohydrates per day to ensure an adequate supply of glucose to the brain.
In the context of the ketogenic diet, the low amount of available carbohydrates forces the body to use lipids as an energy source. More specifically, the organs rely on ketone bodies, which are produced by the breakdown of lipids into fatty acids by the liver to perform their functions. The production of ketone bodies by the liver is called ketogenesis, hence the name of the diet.
The enthusiasm in recent years for the ketogenic diet is mainly due to the results of certain studies that observe that this diet could help with weight loss and may have beneficial effects on certain diseases, such as type 2 diabetes. Let’s take a look together at the state of the scientific literature on the ketogenic diet.
Why weight loss with the "KETO" diet?
In general, the body draws the energy it needs for proper functioning from the carbohydrates consumed throughout the day. In the ketogenic diet, since the body has almost no carbohydrates available, it draws from the carbohydrate reserves stored in the muscles and liver. These reserves, called "glycogen," are associated with a lot of water. For every gram of glycogen used, 3 to 4 grams of water are bound to it. The weight loss at the beginning of the diet is therefore associated with a very significant loss of water.
It is when these glycogen reserves are depleted (that is, between 2 and 4 weeks) that the body begins to draw on its fat reserves to produce energy. However, at this time the body produces waste called "ketone bodies." The accumulation of these ketone bodies in the blood causes a change in breath, similar to that of nail polish remover. This is the main indicator that the body is in ketosis.
The state of ketosis naturally causes a decrease in appetite, and often nausea and fatigue. The decrease in appetite also naturally leads to weight loss.
Allowed and Forbidden Foods in the Ketogenic Diet
These foods are allowed in large quantities on the "KETO" diet:
- Proteins such as: fish, seafood, poultry, and meat.
- Eggs
- Avocado
- Vegetable oils (avocado, coco, olives)
- Butter
- Lemon juice
- Olives
- Low-carb vegetables (spinach, lettuce, kale, etc.)
- Firm cheese (100 g per day)
These should be consumed in moderation in the "KETO" diet:
- Whole milk and yogurt with fat content
- Vegetables higher in carbohydrates (except carrots, sweet potatoes, beets, corn, and peas)
- Wine and alcohol
- Unsweetened coffee
These foods should be avoided in the ketogenic diet:
- Sugar and other sweet products
- Breads, cereals, and , biscuits and pastries
- Potatoes and Starches
- Legumes
- Fruits (except berries)
- Sweet vegetables (beetroot, corn, carrot, etc.)
- Soft cheeses and fresh cheese
- Flavored yogurts
- Soft drinks
- Chocolate, candies, honey, maple syrup, jams
- Fruit and vegetable juice
- Fruit compotes
- Sweet Sauces
- Milk or yogurt made from plant-based drinks (soy, almonds, cashews, oats, etc.)
It is important to aim for a high quality of healthy, quality foods. Fatty foods do not mean foods high in bad fats. Aim for good olive or avocado oils.
The advantages and disadvantages of "KETO"
A literature review conducted by Batch et al. and published in 2020 evaluated the available data regarding the benefits and risks associated with adherence to a ketogenic diet.
According to the studies analyzed, the benefits that can be observed during the first six to twelve months following the implementation of a ketogenic diet include:
- A transient decrease in blood pressure, triglycerides, and glycated hemoglobin
- An increase in HDL cholesterol, the good cholesterol
- A weight loss
According to these same studies, the disadvantages observed following the implementation of a ketogenic diet are:
- An increase in LDL cholesterol, the bad cholesterol, which could increase the risk of developing cardiovascular diseases
- A difficulty in maintaining the diet in the long term, due to severe dietary restrictions
- The benefits observed during the first twelve months are generally no longer present after this period
Finally, the authors of the literature review also mention that most of the studies analyzed were conducted in the short term and on a limited number of participants. Therefore, according to the authors, due to the limited number of robust studies and the lack of solid evidence regarding the potential risks of the ketogenic diet, the use of this diet as a therapeutic intervention should be evaluated by a healthcare professional.
The quantity and quality for "KETO"
As mentioned earlier, the ketogenic diet is low in carbohydrates and high in fats. One of the studies analyzed in Batch's literature review et al. observed the association between carbohydrate intake and mortality. Their results show that low (<40%) and high (>70%) carbohydrate intakes are associated with higher mortality than moderate carbohydrate intakes. Their findings also reveal that mortality is higher when the sources of fats and proteins are of animal origin rather than plant-based. Therefore, it seems that both the quantity of macronutrients and their quality are important.
The OPDQ
In 2018, the Ordre professionnel des diététistes du Québec (OPDQ) published a position statement regarding the nutritional treatment of type 2 diabetes in adults through low-carbohydrate diets. In this publication, the OPDQ notes that most studies on low-carbohydrate diets have been conducted in the short term, that the long-term risks and side effects of these diets are unknown, and that their long-term safety has not been demonstrated. Furthermore, the amount of carbohydrates as well as the quality of macronutrients vary from one study to another. Consequently, the OPDQ reminds that the results of these studies should be interpreted with caution.
In conclusion, before starting a weight loss or therapeutic diet, it is recommended to consult a healthcare professional so that it can be individualized and the necessary follow-up ensured.
References
- Batch, J. T., Lamsal, S. P., Adkins, M., Sultan, S., & Ramirez, M. N. (2020). Advantages and Disadvantages of the Ketogenic Diet: A Review Article. Cureus, 12(8), e9639. https://doi.org/10.7759/cureus.9639
- Seidelmann, S. B., Claggett, B., Cheng, S., Henglin, M., Shah, A., Steffen, L. M., Folsom, A. R., Rimm, E. B., Willett, W. C., & Solomon, S. D. (2018). Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. The Lancet. Public health, 3(9), e419–e428. https://doi.org/10.1016/S2468-2667(18)30135-X
- https://opdq.org/wp-content/uploads/2018/06/Position-Diabete-Diete-Cetogene-1.pdf
- https://www.passeportsante.net/en/Nutrition/Diets/Sheet.aspx?doc=ketogenic-diet