The ketogenic diet is currently probably the most popular diet. It even has its own day. January 5 has been declared Ketogenic Diet Day in the USA. But it should be said that there even dogs in politics have their own day. September 23 is, if you’re interested. Or your dog is.

It exploded in popularity in 2018, and I believe it will now be especially appealing, when people welcomed summer closed in their homes, probably eating more than they should have, and gaining more kilograms than they wanted.

The internet is full of keto recipes and keto menus. This is not yet another of the articles in which you will find them. This is an article in which I will present the advantages and disadvantages of the ketogenic diet, using data from scientific literature.

Ketogenic diet or ketogenic nutrition?

When we talk about any kind of diet or alternative eating regime, it is necessary to distinguish two basic effects. One is the weight loss, which represents the main reason why people resort to diets. The other is the effect on health independent of the number on the scale.

This is important because not rarely behind the health benefits of popular diets hides weight loss. In other words, weight loss has a more positive effect on health than the diet itself. Sometimes it can even hide the negative effect of the diet itself, which comes to light at the moment when an individual finishes with the diet.

Although the words diet and nutrition are often used interchangeably, I will use the first term in the context of weight loss, and the second in the broader context of the way, that is, the regime of eating.

I mention this because the ketogenic diet is not just a diet. It does not promise only the weight loss, but is also presented as a way of eating, and even a way of life.

Mechanism of ketosis

The ketogenic diet is an eating regime based on an extremely low content of carbohydrates, whose goal is to bring the body into a state of ketosis. Ketosis describes the body mechanism through which, as compensation for the lack of carbohydrates, ketone bodies are produced. Ketone bodies are specifically beta-hydroxybutyrate, acetoacetate, and acetone. (1)

The state of ketosis is a natural adaptation of the body to starvation, that is, to the lack of carbohydrates. Although most organs can use fats as a source of energy, the central nervous system, including the brain, cannot, since fatty acids do not cross the blood-brain barrier. Glucose is therefore for it usually the only source of energy. (2)

However, after three to four days of starvation or very low intake of carbohydrates, the central nervous system needs an alternative source of energy, which it gets through ketone bodies. (3) This process is called ketogenesis and mostly takes place in the mitochondria in the liver. (4) By using ketone bodies, the body reduces the need for gluconeogenesis, that is, the creation of carbohydrates from proteins, thereby minimizing the breakdown of muscle tissue.

Determining ketosis

How to know that you are in ketosis? Although there are indications such as bad breath, if you have taken the ketogenic diet seriously, you will want to make sure.

Namely, ketogenic promises are valid only if you are truly in ketosis, and not just on a low-carbohydrate diet. You don’t want all the effort to be in vain because you didn’t cut out those extra 20 g of carbohydrates, do you?

Measuring the level of ketones in the blood (ketonemia) is not practical, which is why most resort to their measurement in urine (ketonuria). Ketonuria is measured with paper strips (e.g. Ketostix) that change color depending on the presence of ketones. It should be emphasized that ketonuria is only an indirect measure of ketosis, which is why its measurement is not always reliable.

When we are already at keto terms, maybe you have also heard of the term ketoacidosis, which can be confused with ketosis. Although these are metabolically similar states, their consequences are significantly different, and they should be distinguished. Ketoacidosis (DKA) is a complication of type 1 diabetes and refers to a life-threatening condition that is the consequence of extremely high levels of ketones and sugar in the blood. This state lowers the pH of the blood, which can damage internal organs.

Rules of the ketogenic diet

The idea of intentionally bringing the body into a state of ketosis rests on the assumption that such a state is superior to the usual metabolic state with sufficient carbohydrate intake. It promises numerous health benefits such as treating diabetes, cancer, Alzheimer’s, then weight loss, improvement of mental performance, better sports performance, etc. Like every good diet, it promises to solve if not all, then at least most of your problems.

In order for the body to enter a state of ketosis, it is necessary to limit carbohydrate intake to 20 to 50 g per day. Also, it is necessary to limit protein intake to a maximum of 25% of energy intake. Otherwise, the body will produce glucose from them and thereby kick the body out of ketosis. (5)

That roughly means that with the ketogenic diet, 80% of daily caloric intake will come from fats, 15% from proteins, and up to 5% from carbohydrates. For a daily intake of 2000 kcal, that would look something like this: 180 g of fats, 75 g of proteins, and up to 25 g of carbohydrates.

The original ketogenic diet uses the ratio of grams of fats to non-fat nutrients (carbohydrates and proteins) of 4:1 or 3:1. Today, less restrictive variants are also practiced, such as the modified Atkins diet and the Low GI treatment. (6)

There are several variants of the ketogenic diet that in certain periods include an increased amount of carbohydrates. One of them is the targeted ketogenic diet, which allows an intake of 30–50 g of carbohydrates around training, in order to prevent a drop in performance. The cyclical ketogenic diet implies 5–6 days of the classic ketogenic diet with 1–2 days of increased carbohydrate intake. (7) Both in some way “admit” the importance of carbohydrates in physical activity.

Another relatively well-known variation of the ketogenic diet is dirty or lazy keto. Simply put, it is a variation that ignores the nutritional quality of the consumed foods and focuses exclusively on their macronutrient composition.

Ketogenic diet and weight loss

One of the main arguments of advocates of keto (or any other LCHF diet) is that the body does not burn fats when carbohydrates are available to it, or does not do it optimally. Therefore, they say, in order to reduce the share of fats in the body, carbohydrate intake should be minimized.

That assumption is not correct. The body always, except in extreme cases, uses a combination of fats and carbohydrates, and even proteins, for energy. In which ratios it will use them depends on the ratios in which we consume them and on the physical activity we engage in.

The fact is therefore that the body in the absence of carbohydrates will burn proportionally more fats. But that does not mean that those fats will be fats from body stores. The obvious error in this logic lies in the fact that we do not burn fats exclusively from our fat tissue, but we also ingest them from the diet. It is not impossible through the ketogenic diet to ingest so many fats that the total caloric intake exceeds expenditure, and that weight loss is absent. We cannot escape from the law of caloric balance.

The ketogenic diet in the context of weight loss gives fast results. If by results we mean the number on the scale. But the number on the scale is not the same as weight loss, that is, the loss of fat tissue. The change in the number on the scale hides changes in the body content of carbohydrates and water.

In order to enter a state of ketosis, it is necessary to reduce carbohydrate intake to a minimum. However, the body does not depend only on the acute intake of carbohydrates, but also possesses their stores. These stores are located in the muscles and liver in the form of glycogen and, in the absence of carbohydrates in the diet, begin to be rapidly spent.

Glycogen in the body is stored bound to water. Each gram of it binds to 2 to 3 grams of water. If we know that the average amount of glycogen in the body is approx. 500 g, we can calculate that its total mass, with the water it binds, amounts to about 2 kg. As glycogen is spent, so is the water bound to it excreted from the body. This explains the initial rapid weight loss on any diet, and especially on those low in carbohydrates.

After the initial stage of accelerated glycogen consumption, the body turns to fats and ketone bodies for energy. Then weight loss significantly slows down. Accumulated fats do not bind water, so their consumption does not give us “extra” loss of body mass. Also, fats contain more than twice as many calories per gram as carbohydrates, so the same energy deficit is reflected in a slower drop in body weight.

The ketogenic diet limits caloric intake well, and it achieves this through two basic mechanisms. First, it is satiating, for which the extremely high amount of fats is responsible. Second, it is very restrictive in terms of the choice of foods. This restrictiveness, that is, monotony, reduces the desire for more of the same food, thereby limiting caloric intake.

Some claim that the ketogenic diet, in the context of weight loss, is superior compared to others. One of the hypotheses is its energetic “costliness.” Authors of this hypothesis claim that using ketones as an energy source requires greater energy expenditure than using carbohydrates and fats, because a certain number of calories is “wasted” on their metabolism. (8) However, this theory has not been confirmed, because the ketogenic diet does not cause a significant change in resting energy expenditure. (9)

Although keto fans will want to convince you otherwise, there is no evidence that the ketogenic diet causes greater weight loss than any other diet with the same energy deficit (10). A calorie is a calorie, and the laws of physics still apply.

Disadvantages and risks of the ketogenic diet

All potentially negative aspects of the “usual” low-carbohydrate diet are amplified in the ketogenic one.

A good portion of those who decide to try the ketogenic diet will experience a set of unpleasant symptoms called the keto flu. It includes physical and mental fatigue, lethargy, dizziness, nausea, vomiting, hypoglycemia, and sleep problems. Keto flu is relatively short-lived and usually disappears within a few days to two weeks.

But the ketogenic diet also carries a number of long-term risks.

Because of the drastic limitation of the number of allowed foods, the likelihood that all your nutritional needs will be met decreases. Eliminating almost all sources of carbohydrates, including fruit, legumes, grains, and certain vegetables, does not only deprive you of carbohydrate intake, but also of numerous macro-, micro-, and phytonutrients. It is not only important what you eat, but also what you do not eat because of what you eat. The opportunity cost of not including these food groups is very high.

Another important problem with the ketogenic diet is the high intake of saturated fats, which causes an increase in LDL in the blood. This increase in LDL is further promoted by the low intake of dietary fiber, which would otherwise mitigate it. True, HDL also increases in the process, but not enough to compensate for the increase in the LDL-to-HDL ratio. This ratio is considered a superior measure of cardiovascular risk compared to individual measures separately.

The list of disadvantages is joined by a series of minor and major problems, such as unpleasant breath (caused by acetone, which is mostly eliminated from the body through breathing), body odor, and irregular heart rhythm. Ketosis during pregnancy could harm the mental development of the child (11), and it is also associated with a lower intelligence quotient. (12) The ketogenic diet can cause the absence of the menstrual cycle in adolescent girls, and even delayed puberty. (13)

In the ketogenic diet, food is divided into allowed and forbidden, into good and bad. This is an excellent basis for developing a negative relationship with food and/or orthorexia.

If you are not friends with food, the ketogenic diet can further worsen your relationship, and it is definitely recommended to avoid it.

The ketogenic diet is extremely impractical. It is restrictive. Demanding. It requires very careful planning. It trips up social gatherings. Therefore, it is almost impossible to follow it long-term, as data from the literature indicate. Even the best diet is useless if you cannot follow it in the long run.

If you decide to try the ketogenic diet despite everything, be sure to supplement it with a multivitamin, multimineral, and dietary fiber.

Keto Adaptation

A term that we inevitably encounter when it comes to the ketogenic diet is keto adaptation. This refers to the process of the body adjusting to the absence of carbohydrates, by using ketone bodies. I mentioned that the body is not exactly thrilled to be without carbohydrates, as evidenced by the keto flu. But fortunately, or unfortunately, it can adapt to this state.

Many of the negative aspects of the ketogenic diet then disappear, and it becomes possible to follow it without excessive suffering. However, let me remind you, we are not only interested in the short-term effects, but also the long-term ones, which do not disappear with adaptation.

Ketogenic Diet and Cancer

Otto Warburg noticed back in the 1920s that most cancer cells metabolize large amounts of glucose into lactate, rather than completely oxidizing it to carbon dioxide, as is the case in healthy cells. It is assumed that this is because this method of metabolism provides various precursors to many biosynthetic pathways, which ensures a constant energy supply to ever-growing cancer cells.

Because of this, many began speculating that first limiting sugar, and then all carbohydrates, could stop this process. In other words, starving the cancer cells, which would then die off. This led to the now popular saying that sugar feeds cancer cells.

If only it were that simple. This theory sounds appealing and may contain some truth, but neither scientific literature nor personal experience confirms it. Although there are certain positive indications in the use of the ketogenic diet for the treatment of some forms of cancer, the small number of studies and their limited quality make it impossible to draw conclusions. (14)

On the other hand, the ketogenic diet can negatively affect cancer prognosis. One of its most dangerous side effects is significant weight loss, i.e., loss of fat and muscle tissue—cachexia. Because of this, cancer nutrition should be sufficiently energy-rich to prevent, or at least minimize, this loss. Under such conditions, it is difficult to take in enough calories on a ketogenic diet, which makes it a bad idea.

Ketogenic Diet and Epilepsy

20–30% of children do not respond to medications for controlling epilepsy. (21) The solution for such cases is the ketogenic diet. It helps more than half of the children whose seizures cannot be controlled by medication alone. 10–15% of them become completely seizure-free. (22)

The use of the ketogenic diet for epilepsy is not limited to children. It is also applied in adults, with somewhat weaker but still good results. (23) The exact mechanism of action is not known.

I mentioned that the ketogenic diet is nutritionally deficient. In order to minimize these nutritional deficiencies as much as possible, and to avoid negatively affecting the child’s development, such dietary therapy should be carried out under the supervision of a nutritionist. Even then, it is not recommended to follow it for longer than 1–2 years.

The ketogenic diet also has its place in the treatment of other neurological seizures, schizophrenia, and some very rare metabolic disorders, such as pyruvate dehydrogenase (PDH) deficiency and glucose transporter type 1 deficiency (Glut1 DS). (24) It is also mentioned in the context of Alzheimer’s and Parkinson’s disease, but research on that is still in its infancy.

Ketogenic Diet and Sport

Carbohydrates used to be the undisputed king of sports nutrition. Or at least they were, until the LCHF, and later the ketogenic, trend appeared. Or should I say—diet.

Carbohydrates form the primary fuel for the body during intense physical activity. The reason for this is that compared to fats, the production of energy (ATP) from carbohydrates requires less oxygen, and oxygen supply represents the main limitation in sports performance.

The problem with carbohydrates is that the body’s stores of them are limited. I previously mentioned that in the general population these stores amount to up to 500 g, and in athletes they can reach up to 800 g. This means that even in the best-case scenario, you will not have more than 3,000 kcal of stored carbohydrates.

On the other hand, the body’s fat stores are practically unlimited. An athlete weighing 70 kg with 10% body fat will store 60,000 kcal in fat. How great would it be if the body could use that as its main fuel instead of carbohydrates, right?

The body will adapt to most conditions, including the absence of carbohydrates. One of the main determinants of which fuel it will preferentially choose is its availability. If you consume more carbohydrates, you will burn more carbohydrates. If you consume more fat, you will burn more fat. It is therefore not surprising that the ketogenic diet, and any other LCHF diet, increases the capacity of muscles to use fat as fuel. (15)

But…

I have already mentioned how fats require more oxygen to release the same amount of energy as from carbohydrates. This leads to a problem, because energy from fats cannot be released as quickly as energy from carbohydrates. Consequently, performance at higher intensities of activity suffers, because energy cannot be produced quickly enough. (16) It is therefore no surprise that the scientific literature points to the absence of benefits for performance. At best, by switching to the ketogenic diet, they remain unchanged. (17) And in the case that you have not gone through keto adaptation, your performance will certainly suffer.

There are indications that keto adaptation could negatively affect the ability of muscles to use glycogen. Logically, if we know that the body conserves energy by the principle of “Use it or lose it,” shutting down metabolic processes that are not used. This means that, if you were to decide to take in carbohydrates before a competition, your body would not be able to use them as efficiently.

The current enthusiasm connected with the ketogenic diet in sport is based on anecdotal “evidence” rather than on the scientific one. The problem with anecdotal “evidence” is that it overlooks many variables that influence the result. A biased individual thinks that one thing led to the result, when in fact it was a set of others. For example:

• Besides switching to the ketogenic diet, he also reduced his weight, which resulted in a better strength-to-mass ratio,
• Switching to the keto diet caused greater discipline, both in diet and in training,
• Placebo effect and excitement about being part of a new culture,
• Actually is not even in ketosis. Carbohydrate intake is significantly higher, although he is not aware of it, especially in periods around physical activity, (18)
• Elevated levels of beta-hydroxybutyrate, one of the main ketone bodies, cause mild euphoria. (19)

It is of great importance to take into account the individual experiences of athletes. However, it is even more important not to fall into the trap of discarding old functional ideas in favor of new, unproven ones just because they are new and popular.

Keto supplements

Keto supplements promise to bring you into a state of ketosis faster than you would by exclusively following the ketogenic diet.

They are available on the market in the form of keto salts and keto esters. Sometimes medium-chain triglycerides (MCT) are also used to induce ketosis. It seems that keto esters are the most effective in raising the concentration of ketone bodies in the serum. (18)

There are indications that supplementation with ketones could actually inhibit endogenous ketone production, which would then produce the opposite of the desired effect. (20)

The ketogenic verdict

The human metabolism is wonderfully flexible in its ability to use different ratios of macronutrients. This flexibility enabled us to survive throughout history. However, the same flexibility is also fertile ground for alternative dietary regimes.

Fashion is an important factor in nutrition.

The popularity of a certain diet or dietary regime depends on how hyped it is, and which celebrity lost weight on it. The ketogenic diet does not follow a different path. It is not better than other diets, it is just new. And novelty is what we crave. The excessive fervor with which it is promoted suggests that it is just another trend. If it sounds too good to be true, it almost certainly is.

I do not claim that it does not work. Because it works. But it works like any other diet, like any other approach to weight loss – by creating a caloric deficit. There is nothing magical in the ketogenic diet.

The question that is not asked often enough is whether such a diet is healthy and sustainable. The answer is negative, to both questions. There are many negative sides to the ketogenic diet, which far outweigh any potential positive ones.

You do not have to eat keto to achieve the results you want. You do not have to bake keto bread or keto pancakes to be healthy.

Stop looking for new diets. Stop looking for health in the wrong place. Contact a nutritionist and arrange your diet according to your individual needs and preferences, without drama and unnecessary restrictions.

References

1.  Bender D. Introduction to Nutrition and Metabolism. Boca Raton, FL, USA: CRC Press; 2014. doi:10.1177/146642400312300118
2. Hartman AL, Gasior M, Vining EPG, Rogawski MA. The Neuropharmacology of the Ketogenic Diet. Pediatr Neurol. 2007;36(5):281-292. doi:10.1016/j.pediatrneurol.2007.02.008
3. Owen OE. Ketone bodies as a fuel for the brain during starvation. Biochem Mol Biol Educ. 2005;33(4):246-251. doi:10.1002/bmb.2005.49403304246
4. Fukao T, Lopaschuk GD, Mitchell GA. Pathways and control of ketone body metabolism: On the fringe of lipid biochemistry. Prostaglandins Leukot Essent Fat Acids. 2004;70(3):243-251. doi:10.1016/j.plefa.2003.11.001
5. Phinney SD. Ketogenic diets and physical performance. Nutr Metab. 2004;1(1):2. doi:10.1186/1743-7075-1-2
6. Kumada T. Modified Atkins Diet and Low Glycemic Index Treatment for Medication-Resistant Epilepsy: Current Trends in Ketogenic Diet. J Neurol Neurophysiol. 2011;s2(01). doi:10.4172/2155-9562.s2-007
7. Ketogena dijeta – kako funkcionira i kako krenuti s provođenjem | Fitness.com.hr. https://www.fitness.com.hr/prehrana/dijete/Ketogena-dijeta.aspx. Accessed June 26, 2020.
8. Feinman RD, Fine EJ. Nonequilibrium thermodynamics and energy efficiency in weight loss diets. Theor Biol Med Model. 2007;4. doi:10.1186/1742-4682-4-27
9. Paoli A, Grimaldi K, Bianco A, Lodi A, Cenci L, Parmagnani A. Medium term effects of a ketogenic diet and a Mediterranean diet on resting energy expenditure and respiratory ratio. BMC Proc. 2012;6(S3):P37. doi:10.1186/1753-6561-6-s3-p37
10. Hall KD, Chen KY, Guo J, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr. 2016;104(2):324-333. doi:10.3945/ajcn.116.133561
11. Institute of Medicine of the National Academies. Healthy Weight Gain During Pregnancy: Reexamining the Guidelines. Washington DC: Institute of Medicine, National Research Council; 2011.
12. L. Kathleen Mahan JLR. Krause’s Food & The Nutrition Care Process. 14th ed. St. Louis: Elsevier; 2017. doi:10.1016/j.jneb.2019.06.022
13. Mady MA, Kossoff EH, McGregor AL, Wheless JW, Pyzik PL, Freeman JM. The Ketogenic Diet: Adolescents Can Do It, Too. Epilepsia. 2003;44(6):847-851. doi:10.1046/j.1528-1157.2003.57002.x
14. Oliveira CLP, Mattingly S, Schirrmacher R, Sawyer MB, Fine EJ, Prado CM. A Nutritional Perspective of Ketogenic Diet in Cancer: A Narrative Review. J Acad Nutr Diet. 2018;118(4):668-688. doi:10.1016/j.jand.2017.02.003
15. Burke LM. Ketogenic low CHO, high fat diet: the future of elite endurance sport? J Physiol. May 2020. doi:10.1113/jp278928
16. Shaw DM, Merien F, Braakhuis A, Maunder ED, Dulson DK. Effect of a Ketogenic Diet on Submaximal Exercise Capacity and Efficiency in Runners. Med Sci Sports Exerc. 2019;51(10):2135-2146. doi:10.1249/MSS.0000000000002008
17. McSwiney FT, Doyle L, Plews DJ, Zinn C. <p>Impact Of Ketogenic Diet On Athletes: Current Insights</p>. Open Access J Sport Med. 2019;Volume 10:171-183. doi:10.2147/oajsm.s180409
18. Burke LM. Re-Examining High-Fat Diets for Sports Performance: Did We Call the ‘Nail in the Coffin’ Too Soon? Sport Med. 2015;45:33-49. doi:10.1007/s40279-015-0393-9
19. Brown AJ. Low-carb diets, fasting and euphoria: Is there a link between ketosis and γ-hydroxybutyrate (GHB)? Med Hypotheses. 2007;68(2):268-271. doi:10.1016/j.mehy.2006.07.043
20. Balasse EO, Neef MA. Inhibition of ketogenesis by ketone bodies in fasting humans. Metabolism. 1975;24(9):999-1007. doi:10.1016/0026-0495(75)90092-X
21. Sillanpää M, Schmidt D. Natural history of treated childhood-onset epilepsy: Prospective, long-term population-based study. Brain. 2006;129(3):617-624. doi:10.1093/brain/awh726
22. Freeman JM, Kossoff EH, Hartman AL. The ketogenic diet: One decade later. Pediatrics. 2007;119(3):535-543. doi:10.1542/peds.2006-2447
23. Lambrechts DAJE, Wielders LHP, Aldenkamp AP, Kessels FGH, de Kinderen RJA, Majoie MJM. The ketogenic diet as a treatment option in adults with chronic refractory epilepsy: Efficacy and tolerability in clinical practice. Epilepsy Behav. 2012;23(3):310-314. doi:10.1016/j.yebeh.2012.01.002