The Primal Diet: from Low-Carb Eating to Health and Fitness

History and Evolution

The concept of the Primal Diet stems from the belief that modern diets, filled with processed foods and excess carbohydrates, deviate from how humans are naturally designed to eat.

For millions of years, our ancestors survived and adapted to their environments by consuming whole, unprocessed foods that were available in the wild. But this trend changed as humans evolved.

The Hunter-Gatherer Diet

Before the advent of agriculture, around 10,000 years ago, humans were hunter-gatherers. It means they relied heavily on hunting animals and gathering wild plants for sustenance.

The majority of their diet was centered around nutrient-dense animal foods, which provided essential fats and proteins. Carbohydrate consumption was relatively low, as grains and refined sugars were not part of their diet, and fruits were only seasonally available. Instead, they ate:

• Meat from wild animals (rich in protein and healthy fats)
• Fish and seafood (high in omega-3 fatty acids)
• Eggs (a complete source of protein)
• Fats from animals, such as tallow and bone marrow

In colder climates, where plant foods were scarce, people relied almost entirely on animal products, further shaping the Primal approach.

Agriculture and Dietary Shifts

With the rise of agriculture, the human diet shifted dramatically. Grains like wheat, rice, and corn became staple foods, and refined carbohydrates became a dominant part of the diet. This shift brought about significant changes in human health:

• Increased carbohydrate consumption led to higher blood sugar and insulin levels.
• Refined foods contributed to metabolic disorders, inflammation, and weight gain.
• Nutrient deficiencies became more common as processed foods replaced nutrient-dense whole foods.

This agricultural shift is viewed as a turning point in human history when humans began to move away from the natural diet that our bodies had evolved to thrive on.

Modern Diets and Chronic Diseases

In recent history, especially with the rise of processed foods in the 20th century, diets have shifted even further from what our ancestors consumed, which aligned with our biology and evolution.

Today, the typical Western Diet is high in refined carbohydrates, sugars, and industrial seed oils, which contribute to a range of chronic conditions like obesity, diabetes, and heart disease.

The Primal Diet seeks to reverse this trend by returning to a way of eating that aligns with how our bodies are designed to function. By focusing on animal-based nutrition and reducing modern processed foods, the diet aims to restore health and improve metabolic function, mimicking the balanced, nutrient-dense diet of our ancestors.

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Our Bodies Are Designed for Nutrient-Dense Foods

From an evolutionary perspective, the human body is optimized to thrive on:

• Animal Proteins and Fats: These provide essential amino acids, vitamins, and fatty acids that are crucial for muscle growth, brain function, and overall health.
• Natural Fats: Such as those from meat and fish, which offer sustainable energy and support cellular health
• Minimal Carbohydrates: As humans historically consumed fewer carbohydrates, our metabolism is better suited for fat as the primary fuel source, with carbohydrates being used sparingly.

The Primal Diet builds on this evolutionary foundation, emphasizing that our bodies are best adapted to do well on the foods we’ve consumed for most of human history: simple, whole, unprocessed, animal-based nutrition, with minimal reliance on modern processed foods.

To reach this eating style, the Primal Diet focuses on three simple rules.

The Core Principles of the Primal Diet

The Primal Diet is built upon three foundational principles:

• Lower Carbohydrates: Reducing processed carbohydrates and sugars to stabilize energy levels
• Higher Fat: Emphasizing healthy fats for energy and cellular health
• Sufficient Protein: Consuming adequate animal protein to support muscle maintenance, repair, and overall bodily functions

The Primal Diet includes a carbohydrate spectrum, and you can choose the Primal Diet level based on the number of carbohydrates you should consume.

The number of carbohydrates suitable for your body is determined based on your metabolic flexibility. Metabolic flexibility means how your metabolic markers are performing and how healthy you are based on these markers, which include blood glucose, waist circumference, blood pressure, HDL cholesterol, and triglycerides.

Among these markers, blood sugar is the most important, as high blood sugar levels can cause insulin resistance, which may lead to a wide range of chronic diseases, from heart problems to cancer.

So, to improve metabolic markers, we need to reduce carbohydrates, but it may be challenging for those used to eating various sources of carbohydrates and sugar for different dietary and health reasons.

Besides dietary and health needs, we need enough protein as we age because, after 30 or 40 years of age, we start losing 1% muscle mass every year or every 10 years, which can cause different health conditions.

To overcome these issues, the Primal Diet provides three main stages to ease you into the process of minimizing carbohydrates and unnecessary foods.

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The Three Levels of the Primal Diet

Based on your health status and carbohydrate needs, the Primal Diet offers three progressive levels, the “Low-Carb Diet,” “Keto Diet,” and “Carnivore Diet,” which you can explore based on your current health status and future goals.

Level 1: Low-Carb Diet (The Foundation)

The Low-Carb Diet is the starting point of the Primal approach, where individuals reduce their intake of refined carbohydrates, such as bread, pasta, and sugar. This level encourages eating nutrient-rich foods like

• Animal Proteins (meat, fish, eggs),
• Healthy Fats (butter, olive oil, avocado), and
• Low-Carb Vegetables (leafy greens, broccoli, cauliflower).

It's an accessible entry point for beginners or anyone seeking to improve their metabolic health and energy balance without drastic dietary restrictions.

This level helps you enter the low-carb world and will improve your mood, mental health, and metabolic function. However, you should progress to the next level if you suffer from serious diseases or need more improvements.

Level 2: Keto Diet (High Fat, Low Carb for Fat-Burning)

The Keto Diet takes the low-carb approach a step further by significantly reducing carbohydrate intake to very low levels and increasing fat consumption.

The goal is to shift the body into ketosis, a metabolic state where fat becomes the primary energy source.

With the Keto Diet, individuals often experience weight loss, stable energy levels, and improved mental clarity. Typical foods include fatty cuts of meat, oils, and low-carb vegetables in moderation.

While this level can provide significant health improvements, you can still experience better results as you progress into the final level of the Primal Diet.

Level 3: Carnivore Diet (All Animal-Based)

The Carnivore Diet is the most restrictive version of the Primal Diet, but it is the ultimate healing protocol as it decreases carb intake to as low as 0-5%. It eliminates all plant foods and focuses solely on animal products. This level includes a diet of red meat, fatty fish, eggs, and animal fats.

As you progress from the Low-Carb Diet to this level, your body gradually adapts to the low-carb lifestyle, and most of the side effects are gone.

This approach can offer benefits like reduced inflammation, improved digestion, and better management of autoimmune conditions. However, careful monitoring is required to ensure proper nutrient intake from suitable food sources.

What Foods Are NOT Allowed on the Primal Diet?

On the Primal Diet, processed foods, grains, refined sugars, and industrial seed oils are strictly avoided. The focus is on whole, nutrient-dense foods derived from animal sources, with occasional low-carb vegetables. Here’s a brief food pyramid:

Base: Red meat, poultry, and fish

Middle: Eggs, healthy fats (like butter, ghee, and olive oil)

Top: Low-carb vegetables and fruits

Consuming these foods and avoiding foods not allowed in the Primal Diet will lead to various health benefits, including weight loss.

Does It Help Weight Loss?

Yes, the Primal Diet can be highly effective for weight loss, particularly because it focuses on reducing carbohydrates, which stabilizes blood sugar and insulin levels.

A 2018 study on the carbohydrate-insulin model (CIM) of obesity found that consuming more high-glycemic foods causes hormonal changes that increase calorie deposition in adipose tissue, boosting hunger, lowering energy expenditure (EE), and resulting in weight gain. So, restricting carbohydrate consumption would promote weight loss [1].

Two other studies conducted in 2016 and 2021 on energy expenditure and body composition changes, and the effect of the ketogenic diet in ad libitum energy intake supported the positive effects of carbohydrate restriction on weight loss [2] [3].

Also, a 2007 study comparing a low-carb diet with other diets found that after 12 months, weight loss was more significant in the low-carb group [4] [5].

Various studies indicate that another reason for the positive impact of low-carbohydrate diets on weight loss is their effect on reducing appetite through nutritional ketosis or influencing hunger hormones ghrelin, leptin, and cholecystokinin [6] [7] [8].

Some studies also suggest that those with higher insulin secretion experience more weight loss due to carbohydrate restriction [9] [10].

Another factor affecting the effectiveness of low-carbohydrate diets in weight loss is the degree of carbohydrate restriction. A 2018 study examined energy expenditure during the weight maintenance phase after participants initially lost 12% of their weight on an energy-restricted diet and then randomly categorized into three groups based on isocaloric carbohydrate intake (high = 60%, moderate = 40%, low = 20) [11].

The results indicated that total energy expenditure was more significant in the lowest-carbohydrate group, and there was a linear trend of 52 kcal/d per 10% reduction in dietary carbohydrates. Calorie restriction also resulted in better triglycerides, HDL-C cholesterol, and lipoprotein insulin resistance [12].

Additionally, higher protein and fat intake support satiety, making it easier to reduce caloric intake naturally.

However, weight management is not the only benefit of the Primal Diet. It can also positively impact hormone regulation, inflammation, metabolism, digestion, the immune system, and mental and cardiovascular health.

The Health Benefits of the Primal Diet

The Primal Diet can provide the following health benefits for containing low levels of carbohydrates.

• Improving Metabolism
• Managing Diabetes
• Reducing Inflammation
• Improving HDL Cholesterol Levels
• Enhanced Mental Disorders
• Improved Digestion

Improving Metabolism

A very low-carbohydrate or ketogenic diet contains about less than 50 g carbs per day (5–10% of total calories), with most of the calories coming from fat (>70%) and the rest (20-30%) from protein.

The human’s central nervous system is dependent on glucose (carbohydrates) to provide energy for daily functions. When you lower your carbohydrate intake to less than 10%, the body will increase fat metabolization and produce ketone bodies as the new energy source (the process known as ketosis).

Ketogenic diets were first used to treat drug-resistant epilepsy, but recently, it has proved to be effective in glycemic control.

Evidence suggests that a ketogenic diet can also be effective in managing type 2 diabetes, promoting blood glucose control, decreasing body weight, and lowering medication needs when compared to low-carb diets [13] [14] [15].

Managing Diabetes

High blood glucose level is one of the most dangerous diseases of our time, as it can be the root cause of a wide range of chronic illnesses, including cancer, heart attack, stroke, kidney problems, nerve damage, and many more.

So, it’s essential to take measures to prevent us from getting diabetes or managing it if we are already infected.

Two vital steps are regular exercise and a healthy diet. Type 2 diabetes is carbohydrate intolerance caused by insulin resistance. So, as different studies have found, carbohydrate restriction is the first step to managing diabetes before medication [16] [17].

Also, finding the proper amount and ratio of macronutrients is necessary to improve glycemic control in individuals dealing with type 2 diabetes [18].

Evidence suggests that low-carbohydrate ketogenic diets can help reduce HbA1c and the need for antihyperglycemic medications in people with insulin resistance and type 2 diabetes [19] [20].

Studies indicate that lowering the consumption of carbohydrates can help decrease blood insulin levels and reverse hepatic insulin resistance [21] [22].

A 2003 study categorized 132 individuals with severe obesity (an average BMI of 43), many of whom also had metabolic syndrome or type 2 diabetes, into two groups: one on a low-fat diet and the other on a low-carb diet for six months.

The results indicated better effect of the low-carb diet on the following metabolic markers [23]:

• Insulin sensitivity improved in the low-carb group but slightly worsened in the low-fat group.
• Insulin levels declined by 27% in the low-carb group but showed a slight rise in the low-fat group.
• Fasting blood glucose levels dropped by 26 mg/dL in the low-carb group but only by 5 mg/dL in the low-fat group.
• Triglycerides decreased by 38 mg/dL in the low-carb group but 7 mg/dL in the low-fat group.

A 2004 study on two groups of 60 overweight individuals, one group following a low-carb diet high in monounsaturated fat and the other following a low-fat diet based on the National Cholesterol Education Program (NCEP) for 12 weeks found that the low-carb group lost 1.8 times more weight and experienced better results in the following markers [24]:

• Triglycerides decreased by 42 mg/dL in the low-carb group but by 15.3 mg/dL in the low-fat group.
• The waist-to-hip ratio (showing abdominal fat) improved in the low-carb group but not in the low-fat group.

Reducing Inflammation

Like diabetes, inflammation is a condition that can lead to various chronic diseases, including autoimmune conditions (such as rheumatoid arthritis), cardiovascular diseases (such as high blood pressure and heart disease), gastrointestinal disorders (like inflammatory bowel disease, Crohn's disease, and ulcerative colitis), and lung diseases, such as chronic obstructive pulmonary disease (COPD) and asthma [25].

A 2014 study on the effect of low-carb and low-fat diets on low-grade inflammation in type 2 diabetes showed that positive impacts on glycaemic control were only observed in the low-carb group.

Also, only the low-carb group significantly improved the subclinical inflammatory state in type 2 diabetes [26].

A 2024 study on the impact of dietary carbohydrates on inflammation-related cardiovascular disease risk suggested that chronic inflammation significantly increases the CVD risk in participants who consumed higher carbohydrates [27].

Improving HDL (Good) Cholesterol Levels

Consuming more fat can increase HDL (good) cholesterol levels. Since low-carb diets include high levels of fat, they can improve HDL levels, which can help improve metabolic health and lower the risk of cardiovascular disease.

Enhanced Mental Disorders

A 2021 study on the effect of ketogenic diets on mental disorders indicated the positive effects of ketogenic diets on psychiatric diseases [28].

Also, lowering carbohydrates can stabilize energy levels, leading to sharper cognition and focus.

Improved Digestion

A 2023 study on the effects of low-carbohydrate diets on obesity and diabetes showed that they have positive impacts on reducing Body Mass Index (BMI) and total body fat mass.

Also, based on the findings of this study, low-carb diets help decrease blood pressure, low-density lipoprotein (LDL), triglycerides, insulin resistance, and fasting blood glucose and HbA1c values, and improve high-density lipoprotein (HDL) levels [29].

A 2014 study on the health impacts of low-carbohydrate diets suggested that, according to the American Diabetes Association, low-carbohydrate diets can boost weight management and metabolic improvements [30].

Despite these benefits, starting a low-carb diet and shifting from carbohydrates to fat may cause challenges and side effects, especially during the initial transition phase and in sensitive individuals.

Common Challenges and How to Overcome Them

Average Americans consume about 300-400 grams of carbohydrates (sugar) per day, which is too much for the body to process, while 1 tsp of sugar daily is enough for our body to function properly.

But when individuals start to lower their carbohydrate intake, say reducing 300-400 g to 50 g per day, they may face side effects like headache, nausea, fatigue, problems with bowel movements like constipation or diarrhea, and reduced concentration because the body is trying to adapt to the shift in fuel, from glucose to ketones (fat).

Also, when you lower your carbohydrate intake, your body loses a significant amount of water because each gram of carbohydrate contains 3 grams of water. So, reducing carbohydrates may cause dehydration, leading to the adverse effects mentioned above.

Some may also experience cravings and Keto Flu (temporary flu-like symptoms as the body adjusts to lower carbohydrates).

To decrease the side effects, you should use electrolytes containing essential minerals like sodium, potassium, and magnesium. You can simply add salt to the water and make electrolyte drinks or use ready-made electrolytes, which provide the necessary minerals and vitamins.

It’s wise to listen to your body and make gradual adjustments as needed. You should also consult a healthcare professional to start with a personalized plan.

How to Start the Primal Diet?

You can simply start with the first level, the Low-Carb Diet, which is easier, progress to the Keto Diet, which lowers carbohydrates, and reach the Carnivore Diet, which is more restrictive, so your body gradually adapts to the shifts in energy sources and experiences fewer side effects.

Also, if you’re trying the Primal Diet to address specific health concerns, you can follow the following rules:

• If you have pre-diabetes, you can start from the Low-Carb Diet.
• If you want to alleviate cancer symptoms, you can start with the high-fat Keto Diet.
• If you’re dealing with autoimmune conditions, you can start with the Low-Carb Diet.
• If you aim to improve your brain and mental function and are suffering from anxiety, depression, or sleep disorders, you can start with a very low-carb Keto Diet.

Whichever level you start with, remember the following tips.

• Gradual Transition: Begin by reducing carbohydrates and replacing them with healthy fats and proteins.
• Sample Foods: For the Low-Carb Diet, consume animal proteins and low-carb vegetables. For the Keto Diet, prioritize fatty cuts of meat and oils and limit carbohydrates further. For the Carnivore Diet, focus on nutrient-dense animal products.
• Be Flexible: Each level of the Primal Diet allows for flexibility based on personal health goals and tolerances.
• Use this free Macro Calculator to decide how many macronutrients you need at each level.

Summary

The Primal Diet offers a powerful, natural approach to nutrition by focusing on whole, animal-based foods and reducing carbohydrate intake.

Whether you're exploring the Low-Carb, Keto, or Carnivore level, the Primal Diet encourages flexibility and experimentation to find what works best for you based on your metabolic markers and the number of carbohydrates your body can process.

Sticking to a low-carb, animal-based diet can lead to long-term health benefits, from weight loss and better digestion to improved mental clarity and energy stability.