Where do carnivores get their carbs from? The surprising metabolic answer

January 5, 2026 •

3 min read

An obligate carnivore like a house cat has a metabolic system that cannot efficiently digest plant carbohydrates, leaving many to wonder how their bodies function. So, where do carnivores get their carbs from when their diet consists exclusively of meat and fat? The answer lies in their remarkable internal biochemistry, which has adapted for this lifestyle over millennia.

Quick Summary

This article explores the unique metabolic adaptations of carnivores, which acquire necessary glucose through gluconeogenesis and from glycogen stored in their prey's tissue.

Key Points

Metabolic Process: Carnivores produce their own glucose through a process called gluconeogenesis, converting protein and fat into the necessary sugar.
Prey as a Source: They also obtain a small, readily available amount of glucose from the glycogen stored in the liver and muscles of their prey animals.
High Protein Requirement: Due to their continuous reliance on gluconeogenesis, carnivores have a naturally high daily protein requirement.
Specialized Digestion: Obligate carnivores lack or have very low levels of carbohydrate-digesting enzymes, making plant matter inefficient for them.
Demand-Driven Glucose: The conversion of protein to glucose is a tightly regulated, demand-driven process that ensures stable blood sugar levels.
Fat Adaptation: The carnivore's metabolism is primarily fat-fueled, a state known as ketosis, with glucose being produced only as needed.

The Core Metabolic Source: Gluconeogenesis

Contrary to popular belief, carnivores are not entirely carb-free. While they do not consume them directly from plants, their bodies possess a sophisticated process to create the necessary glucose. This process, called gluconeogenesis, is the creation of "new glucose" from non-carbohydrate sources. It primarily occurs in the liver but can also take place in the kidneys.

During gluconeogenesis, the liver converts certain amino acids derived from the breakdown of protein into glucose. A smaller contribution also comes from glycerol, a component of triglycerides (fats). This ensures a continuous supply of glucose for vital functions, especially fueling the brain, which relies heavily on it. Unlike omnivores, whose gluconeogenesis ramps up during fasting, a carnivore's metabolism maintains a constant, high rate of this process due to their diet's high protein content. This constant production provides a steady, stable source of blood glucose, avoiding the spikes and crashes associated with high-carbohydrate intake.

The Prey's Hidden Supply: Glycogen

While gluconeogenesis is the primary engine, wild carnivores also gain a small amount of pre-made carbohydrate from their meals. When a carnivore consumes its prey, it ingests not only meat but also organs and other tissues. The prey's liver and muscles contain glycogen, the animal equivalent of starch, which is a stored form of glucose. This source provides an immediate, albeit limited, boost of energy post-meal. For domesticated carnivores, like cats, the food they eat often lacks these organ meats, making their internal gluconeogenesis even more critical for survival. Studies have shown that healthy carnivore diets, like those for dolphins and cats, have evolved to process high protein and low carbohydrate levels efficiently.

Metabolic Adaptations in Carnivores

Carnivores have several unique physiological traits that enable them to thrive on a zero or very low-carb diet. These include:

Loss of key enzymes: Obligate carnivores, such as cats, lack or have significantly reduced activity of enzymes like salivary amylase, which is necessary for breaking down carbohydrates.
Shorter digestive tracts: Compared to herbivores and omnivores, carnivores have shorter intestinal tracts, which are poorly adapted for digesting fibrous plant matter.
High protein requirement: The constant demand for amino acids to fuel gluconeogenesis leads to a higher dietary protein requirement compared to omnivores.

Carnivore Metabolism vs. Omnivore Metabolism


Feature	Carnivore Metabolism	Omnivore Metabolism
Primary Energy Source	Fat and protein.	Carbohydrates, fat, and protein.
Carb Digestion Enzymes	Reduced or absent (e.g., salivary amylase).	Present and active.
Gluconeogenesis Rate	Continually active and high.	Activated during fasting; suppressed after carb intake.
Glucose Regulation	Stable blood glucose via demand-driven gluconeogenesis.	Insulin-dependent blood glucose regulation.
Primary Organ for Glucose	Liver (through gluconeogenesis).	Diet (via absorption from food).

The Role of Gluconeogenic Precursors

Without a steady stream of glucose from food, a carnivore's body relies on a constant supply of raw materials to produce it. The main precursors for gluconeogenesis are:

Amino Acids: The breakdown products of dietary protein, which are processed primarily by the liver.
Glycerol: Derived from the breakdown of triglycerides, the main component of dietary and stored fat.
Lactate: A byproduct of anaerobic respiration, which is converted to pyruvate and then to glucose in the liver.

This robust system is a testament to evolution's ingenuity, allowing carnivores to flourish on a prey-based diet that is naturally low in carbohydrates.

Conclusion: An Evolutionary Adaptation

So, where do carnivores get their carbs from? They get them from themselves. Through the process of gluconeogenesis, their bodies are perfectly adapted to create all the necessary glucose from the fats and proteins in their diet. This, combined with the small amounts of glycogen found in their prey's tissues, provides a complete and sustainable energy model. The high demand for constant glucose production explains why obligate carnivores, such as felines, have a high daily protein requirement and cannot survive on a plant-based diet. The entire metabolic system is designed for a prey-centric lifestyle, demonstrating that a dietary need for glucose does not equate to a dietary need for carbohydrates. Further research continues to uncover the intricate details of this fascinating metabolic pathway. The metabolic link between protein and glucose in carnivores is a subject of ongoing scientific interest and has been studied extensively, as detailed in research published by the National Institutes of Health.

Authoritative Link

For a deeper dive into the specific metabolic differences, especially regarding glucose metabolism in healthy carnivores, readers can explore this article: Normal Glucose Metabolism in Carnivores Overlaps with Insulin Resistance and Type 2 Diabetes in Non-carnivores

Frequently Asked Questions

Yes, carnivores need glucose for certain bodily functions, particularly for their brains. However, they do not need to consume carbohydrates directly through their diet because their bodies are adapted to produce glucose from other nutrients.

Gluconeogenesis is the metabolic process where a carnivore's liver creates new glucose molecules from non-carbohydrate sources, such as specific amino acids from protein and glycerol from fats. This process is continually active in carnivores to ensure a steady supply of glucose.

Yes, indirectly. When a carnivore eats its prey, it also consumes the animal's internal organs and muscles, which contain stored glycogen (a form of glucose). This provides a small, immediate source of carbohydrates.

No, gluconeogenesis is a demand-driven process, meaning the body only creates the glucose it needs. This metabolic regulation ensures a stable blood sugar level, which is different from the insulin spike caused by consuming high amounts of dietary carbohydrates.

Obligate carnivores have evolved without the need to digest plants. They lack or have very low levels of the necessary carbohydrate-digesting enzymes, such as salivary amylase. Their shorter intestinal tract is also not suited for processing fibrous plant material.

A carnivore diet for humans is a form of a ketogenic diet because it eliminates or severely restricts carbohydrates. This forces the body to switch its primary fuel source from glucose to fat, entering a metabolic state of ketosis.

A diet high in carbohydrates can cause digestive upset and negatively impact the metabolic health of domesticated carnivores. Their systems are not equipped to handle a large carbohydrate load and thrive on fat and protein.