...and the food salesmen are really good - they've convinced many a vet of this. Any 'study' by a pet food manufacturer is suspect in itself. Of course they're not going to publish a bad 'study'.
If you look at the ingredients in the RC Glycobalance, the usual 'grain' glutens and flours are used as starches - it's not even 'grain free'. Nothing 'optimum ingredient' about that. Here are the first ingredients (full list on their website): Water sufficient for processing, pork by-products, chicken liver, chicken, wheat gluten, powdered cellulose, gelatin, wheat flour, modified corn starch, natural flavors...
Many much less expensive foods are actually much more appropriate for ANY cat, not just diabetics.
My vet went to Cornell and he's an internist as well as teacher and has some other specialty degrees. He's not just listening to a salesman. I have an open mind about it, and have tried the zero carb stuff and Ricky won't eat it. So what good is that? It might sound good but if a cat won't eat it, it's not worth anything. I know Glycobalance doesn't sound great in the ingredients but I do believe it's a company using science that they have tested.
The dry Glycobalance doesn't have pork product. Here are the ingredients.
Chicken Meal, Barley, Corn Gluten Meal, Powdered Cellulose, Wheat Gluten, Tapioca, Dried Beet Pulp, Chicken Fat, Natural Flavors, Fish Oil, Psyllium Seed Husk, Potassium Chloride, Salt, Fructooligosaccharides, Choline Chloride, Taurine, Vitamins [Dl-Alpha Tocopherol (Source of Vitamin E), L-Ascorbyl-2-Polyphosphate (Source of Vitamin C), Biotin, D-Calcium Pantothenate, Vitamin A Acetate, Niacin, Pyridoxine Hydrochloride (Vitamin B6), Thiamine Mononitrate (Vitamin B1), Vitamin B12 Supplement, Riboflavin (Vitamin B2), Folic Acid, Vitamin D3 Supplement], Trace Minerals [Zinc Proteinate, Zinc Oxide, Ferrous Sulfate, Manganese Proteinate, Manganous Oxide, Copper Sulfate, Calcium Iodate, Sodium Selenite, Copper Proteinate], L-Carnitine, Marigold Extract (Tagetes Erecta L.), Rosemary Extract, Preserved with Natural Mixed Tocopherols and Citric Acid.