I worked for Iams and Science Diet for years.. I am not sure what type you are feeding now but you should give a good premium food a try. I would recommend Science Diet ( best cat food made IMO), Nutro, Wellness, Old Mother Hubbard, or Sensible Choise. these are all premium foods and you should be able to find at least some of them at your local pet store. They are more expensive but they are really worth it. Your cats litter box will smell less also. Some " grocery store" brands have red dye in them that can cause the throwing up. Also, your cat may have a food allergy. Look in the food you feed now and see if it has wheat or corn in it. Those are usually the 2 big culprits. Most of the premium foods should have rice as their grain. No matter what food you choose you should keep them on it for at least a month before you expect any big changes.