Can my healthy cat also eat the prescription food?

Question
I have an 8yr old male DSH who has just started on the Walthams Urinary S/O Diet. The vet has advised him to only have the dried food version (due to being overweight).

Can my healthy (albeit overweight as well) 3yr old female DSH also eat that food? I have tried to feed them seperately, but it isn't working. The healthy one just loves the older ones Walthams food, and now refuses to eat anything else. They both eat better if they share the food, and eat together.

Thanks for the advice.  

Answer
Hi Jo,

I don't think it will hurt your healthy one to be on this diet too, but I would call your vet and see if its okay and if there's any supplements you need to give the healthy cat.  I have several cats on Royal Canin's prescription urinary food but I mix it with some regular (usually Iam's or MaxCat) dry food and my other cats eat it, too.  The urinary formulas are low in protein because protein is hard on the kidneys, so you may need to supplement your healthy cat with extra protein, maybe feed that one some canned food separate from the "kidney cat".  
I would just call the vet and see what he thinks, it may be perfectly all right to feed your healthy cat the Walthams, but call to make sure.