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Protein : fat ratio in dog and cat diets

A short guide to the role of Protein : fat ratio in dog and cat nutrition.

Protein : fat ratio

Protein and fat must be considered together, because it is not only their amounts, but their mutual relation that decides whether the body will use the amino acids to build tissues or burn them for energy. Fat is the densest source of calories in the diet — over twice as much energy as protein [1]. When there is enough fat, it spares protein: the body takes energy from fat, and leaves the protein as building material. When fat is lacking, valuable amino acids go up in flames.

Why the proportion, and not the amount alone

A classic mistake is a diet with a large amount of lean protein and a dramatic deficiency of fat — e.g. slimming on chicken breast alone without skin. This phenomenon is called "rabbit starvation": the bowl is full of protein, and the animal suffers from energy hunger, because there is nothing to cover the caloric requirement [1] [2]. Without adequate fat, the body wastes amino acids on fuel instead of on muscles, enzymes and immunity. That is why a "high protein percentage" alone says nothing if we do not know the fat supply alongside it.

What it means in practice

  • Too little fat relative to protein — the first symptom is dry, flaking skin and a dull coat, and with a chronic deficiency, loss of muscle mass despite eating [1]. The solution: do not pull back the protein, just raise the fat by choosing fattier cuts of meat. In the cat this is more dangerous than in the dog — the cat, as an obligate carnivore, cannot switch off catabolism, so with an energy deficiency it intensively burns protein, which burdens the liver and threatens it with fatty change (lipidosis) [3]. More in the article Fat.
  • Too much fat relative to protein — the risk of obesity and "dilution" of the diet: the animal more quickly satisfies its caloric needs, eats fewer grams and gets too little protein, minerals and vitamins [1]. In predisposed dogs, sudden large jumps in fat increase the risk of pancreatitis. More about the protein side in the article Protein.
  • The myth "too much protein destroys the kidneys" finds no confirmation in a healthy animal — in the cat too low protein is sometimes even more dangerous than moderately high [2]. Introduce changes in the amount of fat gradually, not abruptly.

Sources

  1. National Research Council (2006). Nutrient Requirements of Dogs and Cats. National Academies Press. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
  2. Hand MS, Thatcher CD, Remillard RL, Roudebush P, Novotny BJ (2010). Small Animal Clinical Nutrition, 5th Edition. https://www.markmorrisinstitute.org/sacn5.html
  3. Li P, Wu G (2023). Amino acid nutrition and metabolism in domestic cats and dogs. Journal of Animal Science and Biotechnology 14:19. https://doi.org/10.1186/s40104-022-00827-8