Carnivore diet

The Carnivore diet is a way of eating where the diet consists exclusively or almost exclusively of animal products. It typically includes:

• red meat (beef, pork, lamb), poultry
• fish and seafood
• eggs
• selected dairy products (with minimal lactose content - hard cheeses, butter, cream)

Conversely, all plant foods are completely eliminated – grains, legumes, vegetables, fruits, nuts, seeds, and herbs. This results in a diet composed essentially only of meat and animal products. In practice, there are also exceptions in the form of less strict variants of the diet, which allow some plant foods, typical examples being coffee and spices.
From the perspective of common nutritional recommendations, it is a very extreme regime because it significantly narrows the spectrum of consumed foods in relation to diet diversity, impacting its nutritional quality.

Proponents of the carnivore approach usually stem from several main points:

1. Extremely low carbohydrate intake

By eliminating carbohydrate sources, the body is forced to obtain energy from fats and proteins. After depleting glycogen stores, the body gradually transitions into ketosis, which can last from several hours to days depending on physical activity, glycogen stores, and protein intake. Fats are broken down into fatty acids and ketones, which serve as an alternative fuel for most tissues, including the brain. The high protein intake typical of this diet leads the body to gluconeogenesis (the production of glucose from amino acids). This glucose is necessary for parts of the body that cannot use ketones, such as red blood cells, part of the central nervous system, or the kidneys.

2. Maximum simplicity of the diet

The diet consists of only a few foods, often repeating the same meals. For some people, this simplicity is easier than navigating through many rules and modifications of a regular diet.

3. Elimination of plant “antinutrients”

The argument is that excluding gluten, lectins, oxalates, and other plant substances can calm immune reactions. However, these theories are often oversimplified and scientifically ambiguous.

4. A return to "original" dietary habits

Part of this ideology includes the idea that humans are evolutionarily more carnivorous. The development of the human diet shows, however, that people have adapted to consuming a wide range of foods, not just animal sources.

5. Exclusion of processed foods

This is an aspect that often brings short-term improvement in comfort by itself. By eliminating sweets, baked goods, fast food, and sugary drinks, overall calorie intake decreases, blood sugar levels improve, and energy fluctuations caused by quick carbohydrates subside.

The diet has gained popularity mainly because it promises a simple and clearly defined way of eating, which some people find easy to implement at first glance. The most commonly presented short-term effects include:

• rapid weight loss
• less craving for sweets
• feeling of stable energy throughout the day
• better focus
• subjective relief of some digestive or skin issues

The simplicity also plays a big role, as some people find it easier to adhere to a "just meat" regimen than to navigate common dietary recommendations.

The most frequently mentioned advantages and benefits of the diet include:

1. Easier weight loss

The high protein content increases satiety, most calorie-rich foods are eliminated, and this often results in a naturally lower total energy intake. For some people, reduced cravings for sweets and stabilized blood sugar levels also contribute to easier weight loss.

2. Short-term stable blood glucose levels

For people with insulin resistance, the absence of carbohydrates can temporarily reduce blood sugar fluctuations. Sharp drops in energy after meals are limited, and some people report better focus.

3. Reduction of ultra-processed foods

The diet returns to basic ingredients, which is a certain shift towards better compared to a typical Western diet. By eliminating highly processed foods, the intake of additives, salt, sugar, and trans fatty acids decreases, which can improve digestion and energy in the short term.

4. Subjective relief for some issues

Some people report less bloating, reduced joint pain, or mitigation of skin symptoms. These experiences, however, are very individual and may not have clear scientific explanations. Many short-term benefits can be attributed to reduced overall energy availability, better diet adherence, the elimination of ultra-processed foods, or a temporary effect of changing the gut environment, not necessarily the absence of plants as such.

1. Virtually no fiber intake

Fiber is essential for a healthy composition of the gut microbiome, supports peristalsis, and helps prevent various metabolic and digestive issues. A purely animal diet virtually lacks it, which can cause constipation, reduced production of protective fatty acids in the digestive tract, and gradual changes in the gut microbiota composition, consequently contributing to impaired mucosal barrier function.

2. Risk of deficiency in some vitamins and minerals

The most common risks are deficiencies in:

• vitamin C
• vitamin B1 (thiamine) and folate
• magnesium, potassium
• calcium
• iodine

Many of these substances are typically obtained from plant foods. In a purely animal diet, their intake is significantly lower, and long-term adherence to the carnivore diet can lead to fatigue, immune disorders, impaired recovery, or issues with bones and the thyroid gland. Additionally, with ketosis and reduced insulin activity, there is increased diuresis and thus greater losses of electrolytes. This can increase the risk of fatigue, muscle cramps, or heart arrhythmias. Some of these deficiencies can be compensated by regular consumption of organ meats, marine fish, and selected dairy products, but in practice, many people fail to maintain this long-term.

3. High intake of saturated fats

A diet rich in fatty meat and whole dairy products leads to increased intake of saturated fats, which can raise LDL cholesterol levels. This can lead to an increased risk of cardiovascular diseases in predisposed individuals. Some individuals on the carnivore diet significantly experience increased LDL-C and apoB, indicating a measurable increase in atherogenic burden. Triglycerides can also be elevated in individuals with higher energy intake or genetic predisposition.

4. Changes in gut microbiome composition

Without fiber, bacteria that require it for growth gradually decrease, disrupting their balance. Instead, microorganisms that thrive in a protein- and fat-rich environment may prevail. This can affect the production of protective substances such as short-chain fatty acids, weaken the gut's barrier function, and alter the body's immune responses. The long-term effects of these changes are not yet fully explored, but there is concern that they could contribute to impaired overall metabolism and proper digestive tract functioning.

5. Low diversity and difficult sustainability

Monotony of the diet and limited options in typical settings (eating out, family gatherings, or traveling) make it difficult for most people to maintain this regime long term. Not only is flavor diversity lacking, but also social flexibility, which is important for sustainable lifestyle change. Furthermore, some people may experience mental fatigue from ongoing dietary control or feelings of isolation, as the regime is difficult to integrate into regular social life.

6. Health risks

In some diseases, the carnivore diet can adversely affect treatment. For example, people with type 2 diabetes taking SGLT2 inhibitors (e.g., Jardiance or Forxiga) have a higher risk of euglycemic ketoacidosis with very low carbohydrate intake (a condition where the body produces large amounts of ketones, but blood sugar levels can appear normal, making the problem hard to recognize). Similar situations can occur in diabetics on insulin if they adjust their doses without medical guidance.

For people with naturally higher cholesterol or with a family history, the carnivore diet can cause a rapid increase in LDL cholesterol in a short time. Large amounts of fatty meat, butter, and eggs often exacerbate this reaction.

For individuals predisposed to gout, high intake of meat, broths, and especially organ meats can quickly raise uric acid levels, triggering a painful attack.

For people with chronic kidney disease, this way of eating is unsuitable because the high protein intake significantly stresses the kidneys, which are already working with limited reserve.

In thyroid disorder cases, low iodine and selenium intake and some B vitamins can be problematic. If the diet consists solely of meat, eggs, and dairy products, the body may gradually suffer from their deficiency, potentially worsening thyroid function.

For the carnivore diet, there is a lack of quality long-term clinical studies. Most available information comes from short-term observations and uncontrolled experiments, making it impossible to assess its safety and effectiveness in the long term.