We put our chubby cat on a diet. Not realizing she had been eating so much of the other cats food, the change in calories was more drastic than we had anticipated. Her body shut down, and she became diabetic.

Cats don't know how to explain how they feel, which makes it difficult to gauge when making a dietary change. Yes, your cat will be healthier if you can reduce his/her weight, but please be careful. Giving insulin shots to a cat twice a day is not pleasurable (especially for the cat). A very gradual change in diet is probably best. I would check with the vet for recommendations first.