Do carbohydrates make cats fat and diabetic?

Q: So what does make cats fat?

Energy in excess of energy out. Unglamorous, and it is the answer. The mechanisms that actually matter in an Indian flat are behavioural, not biochemical: free-feeding a bowl that is topped up rather than measured; an energy-dense dry food where a small volume carries a lot of calories; neutering, which lowers energy requirement while appetite stays put; and an indoor cat that walks from the sofa to the window. Our own engine models this as an activity multiplier on maintenance energy precisely because it moves the number more than the ingredient list does. And note the sting in the meta-analysis: if anything is being under-blamed, it is fat , which is energy-dense and drives intake up when

Short answer: no — and this is a post written against our own commercial interest. "High-carb kibble causes feline diabetes" is the most popular argument in fresh-food marketing, ours included by implication. When we went to source it properly, the evidence did not hold. A 2025 meta-analysis found dietary carbohydrate does not increase body fat, fasted insulin or fasted glucose in cats. The driver of feline obesity is eating more energy than the cat spends — and dietary fat may matter more than starch.

Why we are publishing this

Our entire position rests on numbers being checkable. That is worth nothing if we only check the numbers that flatter us. We set out to write the standard carbohydrate piece, went looking for the citation, and found the literature says something different. So this is what the literature says.

What is genuinely true about cats and carbohydrate

Wondering how this applies to your own pet? Build their bowl — two minutes, and it gives the exact grams for their weight.

The metabolic differences are real and well documented. Do not let the conclusion above erase them.

Cats have almost no hepatic glucokinase. Glucokinase is the enzyme that lets a liver take up a large glucose load quickly; its activity is high in dogs, rodents and humans and Hiskett et al. (2009) describes it as nearly absent in the feline liver. Cats rely on the hexokinase system instead. (You will often read that cats lack both — that is wrong, and the glucokinase point is sufficient.)

Their natural diet contains almost no carbohydrate. Plantinga et al. (2011) pooled 55 studies of free-roaming feral cats and derived a prey-based profile of roughly 52% of energy from protein, 46% from fat, and 2% from carbohydrate. Two per cent. Typical extruded dry food runs somewhere in the 40–60% range.

They clear a glucose load slowly. Where a dog's plasma glucose peaks at around an hour and is back to baseline by ninety minutes, a cat's peaks at about two hours and takes four to return.

That is a genuine mismatch between the animal and the food. The question is what it actually causes.

What the evidence does not support

Rankovic et al. (2025), published in the Journal of Animal Science, pooled 16 studies covering carbohydrate levels from 2.8% to 57% of metabolisable energy. Nine measured body fat mass, twelve fasted insulin, fourteen fasted glucose. The conclusion was blunt: dietary carbohydrate is not a risk factor for greater body fat mass or raised fasted insulin and glucose in cats.

The authors go further, and this is the part that matters: increasing dietary carbohydrate does not affect body fat mass in cats. Rather, feeding at an amount greater than the cats' energy requirements, often driven by dietary fats, leads to body fat gain. Their best-fitting model had body fat decreasing as carbohydrate rose as a proportion of energy intake.

On diabetes specifically, obesity is the dominant modifiable risk factor — obese cats carry roughly four times the risk of lean cats — alongside age, male sex, neutering, inactivity and indoor confinement. The rise in feline diabetes tracks obesity and ageing, not the starch content of the bag.

The honest caveats, both directions. The meta-analysis is small — the underlying feline literature is thin — and it measured fasted insulin and glucose, not post-meal responses, which the authors themselves say may be more relevant. One author holds a Royal Canin endowed chair and sits on pet-food advisory boards, which they disclose; we mention it because you should weigh it, not because it invalidates the arithmetic. None of that turns "not supported" into "refuted in our favour."

So what does make cats fat?

Energy in excess of energy out. Unglamorous, and it is the answer.

The mechanisms that actually matter in an Indian flat are behavioural, not biochemical: free-feeding a bowl that is topped up rather than measured; an energy-dense dry food where a small volume carries a lot of calories; neutering, which lowers energy requirement while appetite stays put; and an indoor cat that walks from the sofa to the window. Our own engine models this as an activity multiplier on maintenance energy precisely because it moves the number more than the ingredient list does.

And note the sting in the meta-analysis: if anything is being under-blamed, it is fat, which is energy-dense and drives intake up when food is available without limit.

Then why feed fresh at all?

Because the good reasons were never the carbohydrate. They are:

Water. Cats have a low thirst drive and hydrate poorly by drinking. Fresh food is roughly 70% water by weight, so the water arrives with dinner. This is a real and under-argued benefit, and it does not depend on any claim about starch.
Protein quality and quantity. An obligate carnivore runs gluconeogenesis on protein continuously. Meeting that from animal tissue is different from meeting a percentage on a label.
Knowing what is in it. You bought the ingredients. That matters for elimination diets, for palatability, and for trust.
Portion control by construction. A weighed fresh bowl is a measured bowl. Given that energy excess is the actual mechanism of feline obesity, this may be the largest health benefit on the list — and it is a benefit of how you feed rather than what.

We would rather stand on four arguments that survive scrutiny than five where one collapses.

What a fresh bowl does not do on its own is close the micronutrient gaps — taurine, iodine, zinc, vitamin E, thiamine and the long-chain omega-3s. Those are measured against the NRC 2006 requirement and supplied by weight.

Build your cat's bowl →

References

Rankovic et al. (2025). A meta-analysis: dietary carbohydrates do not increase body fat or fasted insulin and glucose in cats. Journal of Animal Science 103:skaf071.
Plantinga et al. (2011). Estimation of the dietary nutrient profile of free-roaming feral cats. British Journal of Nutrition 106(S1):S35–S48.
Hiskett et al. (2009). Lack of glucokinase regulatory protein expression may contribute to low glucokinase activity in feline liver. Veterinary Research Communications 33:227–240.
National Research Council (NRC). Nutrient Requirements of Dogs and Cats. Washington, DC: National Academies Press; 2006.