Even though high protein/moderate fat/low-carb canned food is a much more species-appropriate diet that is much less apt to cause obesity, a cat that eats more calories than he is burning off will end up with too much fat on his body.
with a very low carbohydrate 50% meat protein grain free dry food.
If you are interested in following a high protein/low carb diet for your diabetic cat, most people recommend that you feed canned cat food. They have always had higher protein and fewer carbs than dry cat food.
Diabetes in Cats: What to Feed Your Pet - Vetstreet
Unlike dogs, cats have a very good chance of becoming non-diabetic if certain dietary changes are made and their insulin resistant factors are controlled (like obesity, etc). It is very common for a cat to require insulin for only a few months and then go into diabetic remission. The two most important recommendations for cats with diabetes are no carbohydrates and no dry food! Diabetic cats should eat a high–protein, moderate fat and low/no carbohydrate food for the best chance of remission from their diabetes. The desired levels may vary if your cat has other medical conditions, but in general, I recommend that at least 45% of your cat's calories come from protein, 25 to 30% from fat and only 10% (or less) of their calories come from carbohydrates. and are great options.
Any cheap lowcarb high protein canned food