Why the feeding guide on the bag overfeeds most cats

Pick up a bag of cat food and the guide on the back gives a portion by weight. Follow it precisely and a lot of cats get steadily heavier.

The guide is not wrong exactly. It is written for an average across all cats, and the average includes intact animals, outdoor hunters and growing kittens. A neutered cat that spends its life indoors sits well below that average, and the gap turns into weight over a year.

The arithmetic the label does not show

Veterinary nutrition starts with resting energy requirement, the calories a cat needs to exist at rest. The formula is 70 times body weight in kilograms raised to the power of 0.75.

For a 4.5 kg cat that is about 216 kcal a day. Then a multiplier accounts for what the cat does with its time. A neutered indoor adult is usually around 1.2, which gives roughly 260 kcal a day. An intact active cat runs nearer 1.4 to 1.6, which is 300 to 350.

That spread is the entire problem. Same cat, same weight, and a difference of almost a hundred calories a day depending on circumstances the bag cannot know.

What a hundred calories looks like

Cats are small, so small errors land hard. A hundred extra calories a day on a 260 calorie requirement is nearly 40% more than the cat needs.

Put another way, a single 10 kcal treat is roughly the same share of a cat’s day as a 150 kcal snack would be for a smaller adult human. The handful of biscuits given casually in the evening is not a rounding error on a cat’s intake, it is a meaningful part of it.

The cat calorie calculator runs the resting figure and the life-stage multiplier together, so you get a daily calorie target rather than a portion weight that assumes a particular food.

Converting calories into food

The target is in calories and the bag is in grams, so the bridge is the energy density printed on the packaging, usually given as kcal per 100 g or kcal per cup.

Dry foods vary enormously, often between 300 and 500 kcal per 100 g, so two foods fed at the same weight can differ by half. This is the main reason a cat gains weight after a food change with no change in portion, and it is invisible unless you look up the density each time.

Wet food inverts it. Most sit nearer 70 to 100 kcal per 100 g because so much of the tin is water, which is why a cat on wet food eats a much larger-looking meal for the same calories.

Weigh the food rather than scooping it

Scoops and cups are where carefully calculated portions go to die. The same cup of the same biscuits varies by a surprising amount depending on how it is filled, and the difference is a reliable few percent either way.

A cheap kitchen scale removes that entirely, takes ten seconds a day, and is the single most effective intervention available to someone trying to manage a cat’s weight. Weigh the day’s total in the morning and feed from it, rather than weighing each meal, which is faster and stops the second person in the house feeding a second full ration.

Treats come out of the total

The working rule used in practice is that treats stay under about ten percent of daily calories, and that ten percent is deducted from meals rather than added on top.

For a 260 kcal cat that is 26 kcal of treats, which is a very small number of most commercial cat treats. Reading the kcal figure on the treat packet once is usually a short, educational experience.

The number is a starting point

Every published formula carries the same caveat, and it is worth taking seriously. Individual cats vary by up to around 30% from the predicted requirement, and nothing on paper tells you which way yours goes.

So treat the calculated figure as a hypothesis. Feed it for four to six weeks, weigh the cat on the same scale at the same time of day, and adjust by ten or fifteen percent if the weight is moving the wrong way. A cat that holds steady on noticeably more or less than the formula suggests is not a failure of the formula, it is the thirty percent showing up.