Let's start with one of my favorite topics: fat pets. I was out this weekend and heard so many stories about how people's pets were fat, but there was nothing they could do about it. They tried giving pet food, but the pet wouldn't eat it. They tried exercise, but the pet just wouldn't do it. Diet food? Too expensive, but didn't work anyway. The only life the pet seemed to tolerate was people food and laying on the couch. Usually this story was presented to me by someone who was not in shape.
However, this article was new to me: Inactivity, Not Dry Food, Leads to Diabetes in Cats. (It's a review of Indoor confinement and physical activity rather than proportion of dry food are risk factors in the development of feline type 2 diabetes mellitis. Singerland LI, et. al. VET J. Oct 2007.)
I know that people blame all kinds of things on pet food, ranging from cancer to behavioral problems. However, this one takes the cake, pun intended. Please listen to me. I'll be as gentle as I can: It's your fault. Now, do some cat's have thyroid issues, sure. But, it's not that common. Is your cat diabetic? Maybe, but the research is clear: your cat was probably fat first, and the diabetes may go away if you get the weight off. Think I'm a jerk? Fine. Prove me wrong. Take your cat to the vet and get the blood tests run. If they all come back normal, odds are you will have no one to blame but yourself.
Time for the good news: you can keep your cat around much longer if you get the weight off. First, ditch the "it's not my fault, he's big boned" attitude. Second, get some light cat food and some ear plugs. Put only the amount recommended by your veterinarian in the bowl and wait. If your cat eats all the food and cries, take the amount he's supposed to get for a day and split it up into 4 or 5 meals. Lastly, encourage the cat to move. Buy a toy or a harness. Pick the cat up from his favorite place in the middle of the day and take him to the opposite end of the house.
This isn't going to be easy, for your or him, I'm sorry. But when is the easy way ever the best way to get something done?