Hi Noobcatlover,
You can try those food with a really heavy smell. I don't recommend RC but if the condition is really bad, you might want to bring to vet to check first cause cat don't show when they are sick. RC indeed have a strong smell and would cause your cat to keep on eating it. Something like junk food and can make them fat.
Other than that, you might want to try Acana or Orijen or Feline Caviar or ANF. They too, have strong smell and they can make your cat fatter. For me, Acana/Orijen(same company), FC and ANF is a lot more better than RC. They are almost the same price and if you see that RC is reasonable, Acana should be too for you.
Hope it helps.