What happens to excess protein on a carnivore diet?

October 20, 2025 •

5 min read

On a carnivore diet, where carbohydrates are virtually absent, the body must find an alternative to convert excess protein into energy. This metabolic process, called gluconeogenesis, is the key to understanding what happens to excess protein on a carnivore diet and how it fuels the body when dietary carbs are not available.

Quick Summary

When an individual on a carnivore diet consumes more protein than needed for body repair, the surplus is broken down into amino acids. These are then converted into glucose by the liver and kidneys through gluconeogenesis, with the nitrogen waste processed by the urea cycle. Proper fat intake helps moderate this process.

Key Points

Excess Protein Conversion: On a carnivore diet, surplus protein is converted into glucose via a metabolic process called gluconeogenesis to maintain stable blood sugar levels for necessary bodily functions.
Nitrogen Waste Excretion: The liver processes the nitrogenous waste from protein metabolism into less toxic urea, which is then filtered and excreted by the kidneys.
Fat is Key for Fuel: The body prefers to use fat for energy on a carnivore diet; sufficient fat intake reduces the need for heavy reliance on gluconeogenesis and promotes ketosis.
Kidney Health Considerations: Consistently high protein can increase the kidneys' workload, potentially leading to issues like kidney stones, especially in individuals with pre-existing conditions.
Balancing Macros for Well-being: Finding the right fat-to-protein ratio, often around 80/20, is crucial for maintaining energy and satiety on the carnivore diet.
Nutrient Density from Organs: To avoid deficiencies from excluding plants, consuming organ meats is important to ensure a broad spectrum of nutrients.
Individual Metabolic Differences: Genetic variations affecting the urea cycle can impact an individual's tolerance for high protein levels.

The Role of Protein on a Carnivore Diet

Protein is an essential macronutrient, providing the amino acids necessary for building and repairing tissues, synthesizing hormones, and supporting immune function. On a carnivore diet, which consists entirely of animal products, protein is plentiful. The body is highly efficient at utilizing what it needs, but the question of what happens to any excess remains. Unlike carbohydrates or fat, the body has no significant storage depots specifically for protein. Any surplus must therefore be processed and repurposed for energy or waste elimination.

Excess Protein and the Gluconeogenesis Pathway

When protein intake is high and carbohydrate intake is very low, as on a carnivore diet, the liver and kidneys can convert excess amino acids into glucose. This process is known as gluconeogenesis, which literally means "the creation of new glucose." While this may sound counterintuitive to someone on a low-carb diet aimed at achieving ketosis, it is a crucial and tightly regulated physiological function.

The steps involved include:

Deamination of Amino Acids: The liver removes the nitrogen-containing amino group from amino acids. This produces ammonia ($NH_3$), a toxic compound, and a carbon skeleton.
Urea Cycle: The liver converts the toxic ammonia into urea, a much safer compound, which is then transported to the kidneys for excretion in urine.
Conversion to Glucose: The remaining carbon skeletons can be converted into glucose. This glucose is then released into the bloodstream to maintain stable blood sugar levels and fuel glucose-dependent cells, like certain parts of the brain and red blood cells.

It is important to note that gluconeogenesis is a demand-driven process, not a supply-driven one. This means the body will not produce an unnecessary amount of glucose just because there is excess protein. Rather, it will only produce what is needed to fulfill metabolic requirements, helping to prevent blood sugar spikes in healthy individuals. The body prefers to use dietary fat for energy on a carnivore diet, which limits the need for extensive gluconeogenesis.

Potential Health Implications of High Protein Intake

While the body has robust systems for handling excess protein, consistently consuming very high levels may pose certain risks, particularly over the long term. Many of these concerns are tied to the increased workload placed on the kidneys and liver.

Increased Kidney Workload: High protein intake results in an increased amount of nitrogenous waste, requiring the kidneys to work harder to filter and excrete urea. For individuals with pre-existing kidney disease, this added stress can be problematic. However, for healthy individuals, evidence suggests that the kidneys can adapt to the increased workload without harm.
Potential for Kidney Stones: Some studies have linked high animal protein intake to an increased risk of certain types of kidney stones. This is due to altered urine composition, including higher levels of calcium and uric acid. The elimination of plant-based foods, which contain protective compounds like citrate, further contributes to this risk.
Nutrient Deficiencies: The absence of plant-based foods, which typically provide fiber, vitamin C, and other essential minerals, can lead to deficiencies if the diet is not carefully constructed to include nutrient-dense animal sources like organ meats.

Balancing Macronutrients on the Carnivore Diet

Successful carnivore dieters often find that balancing fat and protein is key to feeling good and maintaining a steady state of energy. A common strategy is to aim for a higher fat-to-protein ratio, such as the 80/20 ratio (80% of calories from fat, 20% from protein).

High-Fat vs. High-Protein Carnivore Approach


Feature	Higher Fat Carnivore Approach	Higher Protein Carnivore Approach
Primary Fuel Source	Body primarily uses dietary fat for energy, leading to stable ketosis.	Body uses some fat, but relies more heavily on gluconeogenesis for energy, potentially affecting ketosis.
Food Choices	Prioritizes fatty cuts of meat (ribeye, pork belly), high-fat dairy, and added animal fats (tallow, lard).	Emphasizes leaner meats (chicken breast, turkey), with less focus on adding extra fat.
Satiety Levels	High fat content is very satiating, often leading to less frequent eating and fewer cravings.	Protein also promotes satiety, but a lower fat intake might result in less sustained fullness.
Energy Stability	Steady, consistent energy levels fueled by ketones from fat metabolism.	Energy can be stable, but heavy reliance on gluconeogenesis can create more metabolic demand.
Potential Risks	May increase intake of saturated fats and LDL cholesterol.	Higher nitrogen waste puts more stress on kidneys and liver. Increased risk of nutrient deficiencies if organ meats are neglected.

For those who feel unwell on a high-protein carnivore diet, often experiencing "carnivore flu" symptoms like fatigue and nausea, increasing fat intake can often resolve the issue by providing a more efficient energy source. It's crucial to listen to your body and adjust your fat-to-protein ratio accordingly.

Conclusion

On a carnivore diet, excess protein is converted into glucose through a normal metabolic process called gluconeogenesis, with the nitrogen waste efficiently handled by the liver's urea cycle and the kidneys. The body's demand for this pathway is managed largely by the availability of fat for energy. While healthy individuals can generally handle higher protein loads, long-term excessive intake, particularly without adequate fat, may pose risks to kidney function and nutrient balance. Optimizing the fat-to-protein ratio is a key strategy for success, ensuring the body has a stable, preferred energy source and mitigating potential health concerns. A balanced carnivore approach focuses on a variety of animal foods, including fatty cuts and organ meats, to provide both energy and a broad spectrum of nutrients.

Important Considerations

Monitor Kidney Function: If you have any pre-existing kidney conditions, consult a healthcare professional before starting or continuing a carnivore diet due to the increased workload on the kidneys.
Prioritize Fat for Fuel: To prevent over-reliance on gluconeogenesis, ensure your diet includes plenty of animal fats. The 80/20 ratio is a popular guideline for achieving this balance.
Include Organ Meats: Organ meats like liver are crucial for preventing nutrient deficiencies, particularly vitamins that would otherwise be sourced from plants.
Individual Variations: Genetic factors related to the urea cycle can influence how well an individual tolerates and metabolizes a high-protein diet.
Listen to Your Body: Pay close attention to satiety levels, energy, and any digestive issues. Adjusting the fat-to-protein ratio can make a significant difference in how you feel.

Frequently Asked Questions

Gluconeogenesis is a metabolic pathway that allows the liver and kidneys to produce glucose from non-carbohydrate sources, such as amino acids (from protein) and glycerol (from fat). It is a demand-driven process that ensures the body's glucose needs are met when dietary carbohydrates are scarce.

For most healthy individuals, moderate gluconeogenesis from excess protein will not knock them out of ketosis because the body primarily uses fat for fuel and regulates glucose production based on need, not supply. However, excessively high protein intake, especially without enough fat, could potentially impact deep ketosis.

The liver processes the nitrogen from deaminated amino acids, converting the toxic ammonia into a harmless compound called urea. The urea is then transported through the bloodstream to the kidneys, where it is filtered and excreted in the urine.

For individuals with healthy kidneys, the kidneys can typically adapt to the increased workload of processing higher protein levels. However, those with pre-existing kidney disease should exercise caution, as excessive protein intake can worsen their condition. Concerns also exist regarding an increased risk of kidney stones.

On a carnivore diet, consuming enough fat is crucial because it provides the body with its preferred energy source, reducing the need for extensive gluconeogenesis from protein. This allows the body to stay in ketosis and use protein for its primary functions of repair and maintenance.

Not consuming enough fat can lead to the body relying more on protein for energy, which increases the metabolic burden on the liver and kidneys. It can also cause fatigue and other symptoms often referred to as the 'keto flu' as the body struggles to maintain energy levels.

A good starting point for many carnivore dieters is to aim for a ratio where about 80% of calories come from fat and 20% from protein. This can be achieved by choosing fattier cuts of meat like ribeye, pork belly, and short ribs, and using animal fats like butter and tallow in cooking.