It was known well before the discovery of insulin that a low-carb diet would help diabetic humans survive much longer. It's not surprising, then, that low-carb diets are studied in cats and dogs with diabetes. Both dogs and cats are able to convert protein into energy as well as into muscle. The average of most commercial dry pet foods is between 30-70% carbohydrates. Neither species in the wild would have a diet similar to this; both would consume far less than the 30% low-end estimate.