Feed them in seperate rooms and only when you or someone else is
watching?

<< I have cats.  One is on a restricted diet (Hills RD) and the other one on
regular food (Iams).  Any suggestions how to feed them so cat on the diet
doesn't eat the food of the one who isn't? >>

That's a tough one. Feed in separate rooms? Feed both the RD?

www.mimiforsyth.com

The first step is ask the vet if it is harmful for the other cat to
have the RD food.  That may force your choice of how to handle the
situation.   It may force you to put each cat in a separate room to
feed them or to closely supervise them.  

Remember the cat feeding rule: if one cat is eating something the
other cat will automatically want it.

Why not just feed both cats the Hills RD food? It might be more costly,
but it simplifies things a lot, assuming the other cat will eat it.

kill them both, eat them is one big casserole, cats be good eatin....

I have one cat on science diet x/d, 4 cats on science diet c/d. When they
all switched to this food, I had to change them from having dry food in
bowls all day to only getting fed twice a day. They get a mix of wet and dry
(I give them dry for their teeth - they have lots of tartar problems.)
x/d cat gets his food first, up on the counter
c/d cats get their food right after, down on the floor.
It's true, they do want each others' food, but I just watch them for a
couple minutes to make sure they eat 95% of their own food before switching.
It took a lot of training (and whining on their part) but they are finally
used to the twice a day feedings.