The paleolithic ketogenic diet (PKD) is a dietary approach that combines principles of both the paleolithic diet and the ketogenic diet. It aims to mimic the eating patterns of our Paleolithic ancestors while inducing ketosis, a metabolic state where the body primarily uses fat for fuel. This article explores the potential benefits and risks associated with the PKD, drawing upon available research and expert opinions.
Understanding the Ketogenic Diet
The ketogenic diet (KD) is a specialized high-fat, very low-carbohydrate diet with the amount of protein adjusted to one's requirements. By lowering the supply of carbohydrates, this diet induces a considerable change in metabolism (of protein and fat) and increases the production of ketone bodies. The primary ketone bodies are β-hydroxybutyrate, acetoacetate, and acetone. They are produced in the liver (in the mitochondria of hepatocytes) and metabolized in extrahepatic tissues (in the mitochondria of peripheral tissues).
Types of Ketogenic Diets
There is no universally accepted classification of KDs that would precisely indicate the percentage share of each macronutrient. The classic KD is a dietary protocol based on consumption of a considerable amount of fats (80%-90% E), with a concomitant low supply of protein (approximately 6%-15% E) and a very low supply of carbohydrates (approximately 5%-10% E). In the classic KD, the gram ratio of macronutrients, fat to protein and carbohydrates combined, is 3:1 and 4:1, respectively. At a ratio of 3:1, about 87% of energy comes from fat, while at 4:1-it is 90%. The main source of fats is long-chain triglycerides.
To facilitate the diet application, several other variants of the classic KD used in clinical practice have been developed. These present similar efficiency to the original form of the diet. The MCT diet was developed in 1971 as a more acceptable method of nutritional therapy. This diet is dominated by MCTs derived from MCT oil. The medium-chain triglyceride diet (MCTD) guarantees faster absorption of triglycerides into the bloodstream, which results in the formation of more ketone bodies per kilocalorie. Higher efficiency of this process allows for using less fat in the diet and thus allows for more carbohydrate and protein to be consumed, which facilitates long-term maintenance of the diet. In addition, this type of diet improves mitochondrial function.
The MAD is based on a high content of fats relative to other macronutrients, but the ratio of fats varies within much wider boundaries. The ratios of these compounds are not strictly maintained and can range from 1:1 to 4:1. In the MAD, it is assumed that the ratio of fats to carbohydrates and protein combined is 1:1 or 2:1. During the first month of the diet, carbohydrate intake is limited to 10-15 g/day and then increased to 20 g/day.
Read also: Walnut Keto Guide
The Mediterranean ketogenic diet (MMKD) is based on the Mediterranean diet, which emphasizes healthy fats such as olive oil, lean protein sources like fish and lean meat, and limited consumption of fruits and vegetables.
Mechanism of Action
When following a diet containing a balanced amount of fats and carbohydrates, the substrate for ATP production is glucose, which can undergo glycolysis to produce energy or glycogenesis to produce glycogen. During a KD, glucose is replaced by lipid compounds, which leads to a decrease in glycolysis and increases ketogenesis. Ketone bodies are metabolites that are endogenously synthesized during not only adherence to a low-carbohydrate and high-fat diet, but also physiological periods such as short-term fasting or prolonged starvation.
Reducing carbohydrate supply with simultaneous increase in fat intake decreases blood glucose level, which in turn lowers insulin levels. This situation, along with high concentration of adrenaline, leads to the release of free fatty acids (FFAs) from triacylglycerols (TAGs) and glycerol from adipocytes, through the action of hormone-sensitive lipase. Under standard conditions, the acetyl-CoA molecule can be utilized in the Krebs cycle through oxaloacetate-mediated incorporation. However, when the carbohydrate supply is low, the hepatic pool of oxaloacetate is used up for the needs of glucose synthesis in the process of gluconeogenesis. The acetyl-CoA molecule is then used to produce acetoacetate (the first ketone body formed, which is also a precursor for other ketone bodies), which is later spontaneously converted, as a result of decarboxylation, to acetone or reduced to β-hydroxybutyrate by 3-β-hydroxybutyrate dehydrogenase. The produced ketone bodies are released from the liver into the bloodstream.
Ketone bodies are primarily catabolized in the mitochondria of extrahepatic tissues to acetyl-CoA, which is oxidized via the TCA pathway (Kerbs cycle, tricarboxylic acid cycle) and releases energy. In particular, this happens in the heart, skeletal muscles, and brain and constitutes an alternative energy source. Ketone bodies are also directed to lipogenesis or sterol synthesis pathways or are excreted in the urine. The mechanism of energy production participated by ketone bodies is more efficient than with the participation of glucose, due to the fact that ketone bodies bypass the glycolytic pathway by entering the Krebs cycle directly.
The production of ketones is a physiological phenomenon. A state of increased production of ketone bodies is called ketosis. Nutritional ketosis (called “physiological ketosis”) occurs when the blood level of ketone bodies exceeds 0.5 mmol/L. Ketone concentrations in blood can be elevated by such interventions as starvation, KD, prolonged exercise, or fasting. In the morning, after an overnight break, the content of ketone bodies is usually higher and amounts to around 0.4 mmol/L. After prolonged workout or 24-h fasting, this level rises to 1 mmol/L, while with a diet of low-carbohydrate intake as well as during a KD, the concentration of ketone bodies can rise to more than 5 mmol/L. The level of ketosis depends on the type of diet as well as individual predisposition.
Read also: Wine on a Keto Diet
The Paleolithic Diet: A Return to Ancestral Eating
The paleo approach centers on the unprocessed, truly natural foods humans consumed through hunting and gathering in the Paleolithic era, which ended about 10,000 years ago. The food choices can come from meat, fish, poultry, eggs, vegetables, fruits, and nuts. Any refined or artificial products (including healthy oils like olive oil), dairy, grains, legumes, and potatoes are excluded because they appeared after the agricultural revolution that followed the Paleolithic era.
A modern paleo diet includes fruits, vegetables, lean meats, fish, eggs, nuts, and seeds. These are foods that in the past people could get by hunting and gathering. It doesn't include foods that became more common when small-scale farming began about 10,000 years ago. The purpose of a paleo diet is to eat foods likely eaten by early humans. Farming made foods such as grains and legumes more easily available. And it introduced dairy. Also, farming changed the diets of animals that people ate. The paleo diet idea is that these changes in diet outpaced the human body's ability to change, or adapt.
Foods Included
In general, a paleo diet has many features of recommended healthy diets. Common features the paleo diet has include the emphasis on fruits, vegetables, lean meats, and the avoidance of processed foods.
Foods Excluded
The main concern about paleo diets is the lack of whole grains and legumes. These foods are considered good sources of fiber, vitamins, proteins, and other nutrients. Also, low-fat dairy products are good sources of protein, calcium, vitamins, and other nutrients. Whole grains, legumes, and dairy also are generally more affordable and available than foods such as wild game, grass-fed animals, and nuts. For some people, a paleo diet may be too costly.
Combining Paleo and Keto: The Paleolithic Ketogenic Diet
The Paleolithic Ketogenic Diet combines the principles of both diets, focusing on foods that were likely consumed by our Paleolithic ancestors while also restricting carbohydrates to induce ketosis. This typically involves a diet rich in animal products (meat, fish, eggs), non-starchy vegetables, and healthy fats, while excluding grains, legumes, dairy, and processed foods.
Read also: The Keto-Brain Fog Link
Potential Benefits of the PKD
Weight Loss
The ketogenic diet (KD) has gained immense popularity during the last decade, primarily because of its successful short-term effect on weight loss. Minimizing the intake of carbohydrates results in the reduced absorption of simple sugars, thereby decreasing blood glucose levels and fluctuations of glycaemia in diabetes. Studies on obesity indicate an advantage of the KD over other diets in terms of weight loss. This may be due to the upregulation of the biological activity of appetite-controlling hormones, or to decreased lipogenesis, intensified lipolysis and increased metabolic costs of gluconeogenesis.
KD has been shown to effectively lead to weight loss, reduction in hyperinsulinemia, and improvement in insulin sensitivity.
In a systematic review and meta-analysis of clinical trials performed by Santos et al., a total of 23 randomized controlled trials corresponding to 17 clinical investigations were analyzed. The authors concluded that LCD has positive effects on body weight, BMI, abdominal circumference, blood pressure, high-density lipoprotein cholesterol (HDL-C), triglycerides, glycemia, hemoglobin A1c (HbA1c), insulin, and C-reactive protein (CRP). In another meta-analysis performed by Bueno et al., a total of 13 randomized controlled trials were examined. The authors reported statistically significant results in the first six months of intervention, but at longer periods of 12-24 months, the statistical significance of outcomes decreased.
Neurological Benefits
The beneficial effects of the KD on neurological diseases are related to the reconstruction of myelin sheaths of neurons, reduction of neuron inflammation, decreased production of reactive oxygen species, support of dopamine production, repair of damaged mitochondria and formation of new ones.
Every therapeutic action taken in diseases of the nervous system is aimed at slowing down or completely stopping the process that leads to the degeneration and death of neurons (neuroprotective actions). The beneficial effects of the ketogenic dietary therapy on neurological diseases result, inter alia, from the reconstruction of neuronal myelin sheaths, in the reduction of neuron inflammation, reduction of reactive oxygen species (ROS) production, promotion of dopamine production, repair of damaged mitochondria (which affect the disturbed neuronal metabolism in the course of numerous neurological diseases) and formation of new ones. Additionally, the ketogenic dietary therapies provides neurons with an alternative energy source in the form of ketone bodies, which is extremely important because glucose absorption, transport and metabolism are most often impaired in neurological diseases.
Many studies suggest the relevance of the KD as an element of adjunctive therapy in the treatment of diseases of the central nervous system, due to the diet's effects on modulating inflammation, controlling pro-oxidant-antioxidant balance or altering the composition of the gut microbiome. This mechanism of action of the KD affects a number of neurological diseases, such as epilepsy, Alzheimer's disease (AD), Parkinson's disease, depression, migraine and multiple sclerosis (MS).
Improved Metabolic Health
KD has been shown to effectively lead to weight loss, reduction in hyperinsulinemia, and improvement in insulin sensitivity.
As reported by Seidelmann et al. in a prospective cohort study and meta-analysis, it is not only a matter of CHO restriction but also the quality of food ingested. The study’s primary outcome measure was all-cause mortality. After multivariable adjustment and a median follow-up period of 25 years, a U-shape association was observed between the percentage of energy consumed from CHO and mortality [pooled hazard ratio (HR): 1.20 (95% CI: 1.09 to 1.32 for low CHO consumption); pooled HR: 1.23 (95% CI: 1.11 to 1.36 for high CHO consumption)] in the Atherosclerosis Risk in Communities (ARIC) cohort. The authors emphasized that both low (<40%) and high CHO consumption (>70%) conferred higher mortality when compared with moderate CHO intake. Further analysis of the results demonstrated that mortality was worse when fat and protein sources were animal-derived instead of plant-derived.
Potential Therapeutic Applications
There are a number of studies on the use of the KD in various disease entities, mostly related to neurological diseases. The use of the KD dates back to the early 1920s, when Russell Wilder developed a diet that mimicked the body's metabolic state during starvation and proposed its use in patients with epilepsy. This was when the term “ketogenic diet” was first used. With the subsequent development of antiepileptic drugs, its application was no longer common.
The literature also discusses the use of the KD in psychiatric diseases, such as severe anxiety, depression, active bipolar disorder with psychosis or schizophrenia. Ketones are potentially a neuroprotective factor, primarily due to reduction of inflammation in the body and maintenance of stable blood glucose levels. However, these studies are limited to single cases or small groups, and the duration of the diet is short.
AD is a type of dementia of a multifactorial origin. It has been demonstrated that the KD can have a beneficial effect on AD, affecting many bodily processes. Consumption of high-glycaemic-index foods promotes the accumulation of β-amyloid in the brain; hence, the KD may have a neuroprotective effect in AD.
KD has been postulated to positively impact women diagnosed with polycystic ovarian syndrome (PCOS). In turn, treatment is targeted towards improving insulin resistance, weight loss, decreasing luteinizing hormone (LH) and follicular stimulating hormone (FSH) ratios, and excess androgens.
Potential Risks and Considerations
Nutrient Deficiencies
Because of the stringent food restrictions, many find the keto diet hard to stick to. “Because the keto diet is so restricted, you’re not receiving the nutrients - vitamins, minerals, fibers - that you get from fresh fruits, legumes, vegetables and whole grains,” says Dr. Ring.
Following a keto diet can also cause your blood sugar to drop, which can be dangerous for people living with diabetes. Common symptoms of low blood sugar include weakness or shaking, sweating, a fast heartbeat and dizziness.
The keto diet lacks fiber and several micronutrients due to the severe restriction of foods that contain carbohydrates.
People following any diet that eliminates food groups should make sure they are meeting their daily nutrient requirements to avoid deficiencies.
The "Keto Flu"
Common short-term side effects resulting from the initiation of KD have been referred to as “keto flu,” which encompasses symptoms including fatigue, headache, dizziness, nausea, vomiting, constipation, and low exercise tolerance. Symptoms typically resolve after a few days to weeks as the body adjusts to the low CHO, ketogenic state.
People following the keto diet may experience side effects related to entering a state of ketosis. These include keto breath, a keto skin rash, and the “keto flu.” Symptoms off the keto flu include headaches, lethargy, nausea, mental slowness, insomnia, decreased exercise performance, constipation, and low libido.
Cardiovascular Concerns
The high-fat nature of the diet could also have negative impacts on heart health. The American Heart Association recommends limiting saturated fat intake to less than 6%. “In practice, many people eat high amounts of saturated fats, which could increase your risk of heart disease,” says Dr. Cheema. “You may be eating a lot of fatty meat thinking it’s a good thing for you because it's high in fat. This can dramatically alter your lipid profile. While high-fat diets can elevate LDL (“bad”) cholesterol, the type of saturated fat matters. The bottom line is that having more fats in your diet can lead to higher cholesterol. “We know that higher cholesterol tends to increase your chances of heart attacks and strokes,” says Dr. Cheema.
Also, participants following a very-low-carbohydrate ketogenic diet (VLCKD) had a significantly greater increase in low-density lipoprotein cholesterol (LDL-C) levels when compared to participants following a low-fat diet (LFD) (95% CI: 0.04 to 0.2; p=0.002). The lack of evidence regarding long-term cardiovascular implications indicates that making recommendations against or in favor of KD should be a topic of further discussion.
Distinguishably, increases are observed with LDL-C and total cholesterol. Conversely, LDL-C and total cholesterol changed more favorably in the LFD group after six months of the intervention.
Sustainability and Long-Term Adherence
Long-term adherence to KD is a major challenge and that is why this type of diet is considered non-sustainable.
Because of the stringent food restrictions, many find the keto diet hard to stick to. “The ketogenic diet can be effective for weight loss when used in a short time period followed by the adoption of healthier eating habits,” says Baljash Singh Cheema, MD, a cardiologist at Northwestern Medicine Bluhm Cardiovascular Institute. “However, we know in studies of these types of diets that once people stop following that diet, they regain at least half of the weight that they lost.
Kidney Issues
The keto diet may not be appropriate for everyone, specifically people with kidney disease. “Although more research is needed in that area, there is some suggestion that it can make kidney disease worse over time,” says Dr.
Other Potential Side Effects
Some people also experience dehydration on the keto diet because they’re eliminating glycogen, which holds water, from the bloodstream.
The keto diet can cause your blood pressure to drop in the short term due to a reduction in blood volume and changes in your fluid balance. Symptoms of low blood pressure include dizziness, lightheadedness or fainting, especially when standing up quickly.
Psychological Considerations
When you micromanage your food intake by tracking how much you eat, it disconnects you from what your body is asking for. You start using outside numbers to determine what to eat instead of listening to your body. “Being intuitive and understanding what your body needs is essential for proper nourishment,” says Merneedi. Monitoring food so closely can lead to psychological distress, such as shame and binge eating.
Comparing the PKD to Other Diets
Keto vs. Paleo
Keto and paleo diets share some similarities, but there are also differences. The differences between keto and paleo diets are in the foods they allow, their effects on the body, and key health effects.
The ketogenic (keto) diet focuses on eating a particular balance of macronutrients. The goal is to enter a state of ketosis, where the body begins to burn fat for health or weight loss.
The Paleolithic (paleo) diet focuses on eating foods that humans would have eaten in the Stone Age. The goal is to eliminate modern processed foods for health or weight loss.
For instance, the National Institutes of Health (NIH) and American Heart Association recommend a daily intake of whole grains, which are not a part of keto and paleo plans.
Keto vs. Carnivore
A carnivore diet is the most ketogenic because its carb content is extremely low, which is why it's sometimes called the "zero carb" diet. You only eat meat, poultry, eggs, fish, and dairy.