One important way of looking at the quality and appropriateness of a particular diet is to analyze the percentages of macronutrients. The term “macronutrient” refers to the main components of any diet and includes protein, fat, and carbohydrates.
Looking at the macronutrient content of a pet food is invaluable but does not tell the whole story. For example, such an analysis does not tell you about the quality of those ingredients or the amounts of micronutrients such as vitamins, minerals, and phytochemicals. Having acknowledged the shortcomings, let’s take a crack at pet food macronutrients.
The most helpful way of looking at macronutrients is to calculate what percentage of the calories in the food each macronutrient provides. In the literature this is referred to as the percentage of metabolizable energy or % ME. For the sake of your sanity, I am going to skip the mathematical calculations required to determine these numbers.
Suffice it to say that if you were feeding a pet food that consisted of 30% ME protein, 30% ME fat, and 40% ME carbohydrates then for every 100 calories your pet eats, 30 calories would come from protein, 30 calories would come from fat and 40 calories would come from carbohydrates.
According to a meta-analysis of 27 studies that analyzed the food (mostly birds and rodents) eaten by feral, domestic cats, their diets consist of 52% ME protein, 46% ME fat and 2% ME carbohydrates. The authors further state, “The calculated nutrient profile may be considered the nutrient intake to which the cat’s metabolic system has adapted.”
Millions of years of evolution have intelligently designed cats to eat low-carbohydrate diets. Their metabolism is geared to be fueled by protein and fat. You should never mess with Mother Nature!
Meanwhile, the AAFCO nutrient profile for adult cat food consists of 25% ME protein, 21% ME fat and a whopping 54% ME carbohydrates. This is nowhere near the percentages that the cat’s metabolic system has adapted to.
What kind of food does your cat eat?