Flip over any bag or pouch of cat food and you will find a panel of percentages. Crude protein, crude fat, fibre, moisture. Almost nobody explains what those numbers should look like, or why. So start where every good feeding decision starts: with what a cat is built to run on.
The three numbers that matter
Macros are the nutrients that supply energy: protein, fat and carbohydrate. Every animal runs on a mix of the three. The question is which mix.
For cats, science has measured the answer twice, from two different directions.
First, from the wild. A 2011 analysis in the British Journal of Nutrition reconstructed the diet of free-roaming feral cats from 27 field studies. The result: 52 percent of daily calories from protein, 46 percent from fat, 2 percent from carbohydrate.
Second, from the lab. In the same year, researchers gave domestic cats free choice across foods with different macro profiles. Left to build their own diet, the cats converged on roughly 52 percent of calories from protein, 36 percent from fat and 12 percent from carbohydrate. The study also found a carbohydrate ceiling. Past a fixed daily amount, cats stopped eating, even when it cost them protein.
Ecology and behaviour arrive at the same shape independently. Protein leads. Fat carries the rest. Carbohydrate barely registers.
Protein is not a preference
Cats burn protein around the clock. The liver enzymes that break down amino acids run at a permanently high rate, and unlike omnivores, cats cannot dial them down. Feed a cat too little protein and it does not adapt. It starts drawing on its own muscle.
How much is enough? The official minimums are lower than most owners expect. AAFCO sets adult maintenance at 26 percent protein on a dry matter basis. Minimums exist to prevent deficiency. They do not describe the best version of the animal. A 2013 study measured the gap directly: around 1.5 grams of protein per kilogram of body weight keeps a cat in nitrogen balance, while roughly 5.2 grams per kilogram is needed to hold on to lean muscle. A cat can pass the minimum and still slowly lose muscle.
That is the difference between surviving and thriving, written in grams.
Fat does the quiet work
Fat is the second fuel and the densest one. It carries the fat-soluble vitamins, supplies the fatty acids cats cannot make themselves, including arachidonic acid, and keeps skin and coat in condition. It is also the reason food tastes like food to a cat.
The official floor sits near 9 percent fat on a dry matter basis. Nature runs far higher. Nearly half of a feral cat's calories come from fat. A protein-led diet with generous animal fat is not indulgence. It is the shape of prey.
The requirement that does not exist
Open the three main nutritional standards for cats: NRC, AAFCO and FEDIAF. You will find minimums for protein, fat, every essential amino acid, vitamins and minerals. You will not find a carbohydrate requirement. There is none.
Cats build their own glucose from amino acids through a process called gluconeogenesis, and they do it so efficiently that even pregnant and nursing cats meet their glucose needs from protein.
Carbohydrate is not poison. Recent research, including a 2025 meta-analysis, shows cats tolerate moderate amounts without gaining fat or losing blood sugar control. The honest statement is simpler. Carbohydrate is the one macro a cat has no use for. Every percent of it takes space that protein and fat should fill.
Moisture, the macro nobody counts
A mouse is roughly 70 percent water. That number matters, because cats descend from desert hunters that got their water from prey more than from ponds. The species carries a famously weak thirst drive. A cat fed dry food does not voluntarily drink enough to close the gap.
Moisture sits on the label like an afterthought. Read it like a macro. Dry food holds around 10 percent moisture. Wet and raw diets hold around 70 to 75 percent, the territory of prey. When you compare foods, compare this line first.
Size changes the amount, not the recipe
A five kilogram cat does not need different macros from a three kilogram cat. It needs more of the same ones.
The ratios are fixed by biology. The quantities scale with body weight. Using the lean muscle benchmark of 5.2 grams of protein per kilogram per day, a 3 kilogram cat needs about 16 grams of protein. A 4 kilogram cat, about 21. A 6 kilogram cat, about 31.
Breed follows the same rule. A Maine Coon and a Siamese are built for the same protein-led, low-carbohydrate profile. The Maine Coon simply eats a bigger portion of it. Age, activity and neutering move the calorie total up or down, and the macros ride along at the same ratios.
The team at Bangkok Cats, a world championship cattery, raises champions and kittens on this exact logic. Protein first. Fat close behind. Carbohydrate near zero. Water built into the food. Not because it is fashionable, but because it is what the animal is.
Next time you pick up a pack, skip the front. Turn it over and read four lines: protein, fat, carbohydrate and moisture. The label tells you what the food is made of. Now you know what it should be.
