I feed 2 cups (give or take) to 3 kittys during a normal day. I use a large soup spoon when measured out it equals 1/3 cup (3 spoon fulls). Also depends on the size of your food. Nutro that I feed has big pieces so little goes a long way. Smaller the food piece size obviously the more that will go into a bowl. 1/3 measuring is about 25 pieces of food using Nutro.

The better quality food less calories/fat. Unfortunately the store rt brand at our house put weight on and Science Diet Light did also. However, Nutro has not. The less byproducts the better.
If it starts out with "corn byproduct, beef byproduct" your getting allot of fillers (SD uses byproducts).

I am dealing with Eleanor who thinks all the food is hers.
If between her and Skinny the two bowls get eaten and Thumper has slept through the meal time , she gets 2 soup spoon meal for herself.

The quality of food has allot to do with weight along with portion.
In my opinion and experience.

I encourage play and exercise.