Most cat experts recommend premium brands of cat food that avoid ingredients like by-products and chicken meal, etc. However, feral cats eat a whole rodent or whole bird. Sometimes they leave things like feathers or the head behind, but otherwise, the cat is consuming the whole body of an animal. It seems like the cheaper brands, as long as they don't contain carbohydrate fillers, would be closer to a natural diet than the premium brands in this case.
Why isn't this the case?
Byproducts in Cat Food
While it's true that cats in the wild eat the whole bodies of their catch (including the heads in some cases), the term " meat by-products" has become a "dirty word" to many cat experts, because of its misuse by some members of the cat food industry. As a result, experts have traditionally counseled readers to avoid all by-products for this reason. (If you get a chance to read Ann Martin's gruesome but eye-opening book, "Food Pets Die For," you will see examples of the sort of things food manufacturers can legally put into their foods under the classification of "meat byproducts."
The founders of the Feline Future website analyzed the ingredients and nutritional properties of foods cats eat in the wild over a period of a decade or more, and the result was their "recipe" for the Feline Future raw food diet for cats - one which has set the standards for raw feeding, to this day.
Actually, they do use a larger proportion of meat to internal organs. In addition, chicken hearts and livers (which are excellent sources of taurine) are added in limited quantities, because of the dangers of "overdosing" with Vitamin A.
In a nutshell, a named by-product may possibly be acceptable, e.g. "chicken by-product meal" but it should not be listed as the first ingredient in cat food.
Unfortunately, labeling laws being what there are, there is no way to know the exact proportion, by weight, of any individual ingredient. Although it is possible to define "protein" as 30% of the product's weight, that protein will include meat, by-products, eggs, certain grains, and other forms of protein in the can or bag of cat food. As a result, it's better to see the named by-products relatively far down on the label.
As for the "cheaper brands," unfortunately most of them do contain large amounts of carbohydrate fillers in dry cat food, usually in the form of corn, which is commonly known to be a) difficult for cats to digest and b) implicated in food allergies, probably as a result of "a."
However, in fairness to the "cheaper brands," many premium brands of dry food contain large amounts of carbohydrate fillers. It's the nature of the beast. In the manufacturing process of extrusion (which is a heat-based process), it is necessary to have these dry ingredients in order to effectively shape the dry food nuggets. Some brands of "dry" food do not use grain fillers. Notable examples are listed in Grain-Free Dry Cat Foods, although some of these foods are not carbohydrate-free.