Macronutrients are the foundation of every diet. In dogs and cats, true macronutrient needs come from a combination of evolutionary history, digestive enzyme profiles, metabolic pathways, and tissue requirements. Industrial processing, convenience formulations, and marketing trends often conflict with these biological principles.

Dogs and cats thrive on diets rooted in animal tissues. The digestive physiology of dogs and cats are built for protein and fat metabolism, not carbohydrate-heavy foods.

One of many things dogs and cats have in common is that dogs and cats are carnivores, protein is the most biologically important macronutrient for both species.

Protein supports:

Dogs and cats require more protein than omnivores because their metabolic systems run on amino acids at higher rates.²

Key species differences:

Protein deficiency leads to reduced immunity, poor coat quality, muscle wasting, metabolic slowdown, and impaired healing.

Every biological process depends on protein. It creates:

Cats require taurine, arginine, and several other amino acids preformed from animal tissues. They cannot synthesize them in meaningful amounts.

AAFCO’s adult dog maintenance requirement for crude protein is only 18 percent on a dry matter basis¹. This represents the lowest threshold before clinical deficiency develops.

This is the lowest threshold below which dogs develop protein deficiency diseases.

Feeding a diet at the minimum:

It is comparable to feeding humans the caloric equivalent of instant noodles. Technically adequate. Not health promoting.

Optimal health requires substantially higher levels of high-quality animal protein.

Both species are carnivores, but their protein needs differ.

Dogs:

Cats:

Cats require more protein per body weight than nearly any domestic species.

Fat serves as a concentrated energy source and plays a central role in cellular structure, hormone synthesis, and nutrient absorption.

In carnivorous mammals:

Both dogs and cats efficiently derive metabolic energy from fat, particularly when diets are low in refined carbohydrates.

Certain fatty acids must be obtained directly from the diet.

This distinction further reinforces the obligate carnivorous status of cats and their dependence on animal-based ingredients.

Dogs and cats both possess the ability to digest carbohydrates to some degree. However, health impacts of processed pet food and digestive capability does not equate to nutritional necessity.

Key distinctions:

Dogs exhibit greater tolerance for starch digestion due to pancreatic amylase activity. Cats demonstrate limited enzymatic flexibility and rely predominantly on protein-derived glucose.

This is the single most misunderstood aspect of canine nutrition.

Carbs are:

Dogs convert fat and protein into glucose via gluconeogenesis, a metabolic adaptation specifically evolved for carnivores.⁶

Carbs → glucose → insulin → fat storage.

Extrusion requires starch for binding and shaping. That means:

Kibble is 30% to 60% carbohydrates

This level far exceeds biologically appropriate intake for either species and increases digestive and metabolic stress over time.

Biological balance is achieved across feeding periods, not within individual meals. Wild carnivores experience natural variability in macronutrient intake depending on prey availability and composition.

Short-term variation does not equate to deficiency when diets are based on whole, nutrient-dense animal foods consumed in appropriate ratios over time.

Dogs and cats thrive on diets rich in animal protein and healthy fats. Carbohydrates function as optional energy sources, not nutritional necessities.

Understanding these fundamentals helps pet parents evaluate modern diets with a clear biological lens.