Over Eating

This cat had a kidney infection 3 years ago that was successfully treated with antibiotics.
She was very sick and was not eating or drinking for several days.  I had to give her fluids under her skin.
She made a fairly complete recovery but is always meowing for canned food.  I gave her the special diet from the vet but couldn't afford the cans long term (it came to $1.50 a can).  I researched the lowest protein for canned food and have used various brands.  The incessant meowing seems to me to be not really hungry but having stomach pain.  Have tried antacids (crushing Zantac in recommended amount and adding to food) which seems to help some, and mixing food with rice and peas.
She has gained a lot of weight. She is other wise healthy - good coat, clear bright eyes, purrs a lot, good mobility except for the weight. So the problem is keeping the appetite under control which I don't think is true appetitie.  Is there some other supplement or antacid that would help?  The real question is why is she meowing as if hungry?

[Justine Lee, D.V.M., DACVECC]

If you can't afford a specific low-protein diet, I'd actually be ok with buying canned food (any normal adult cat food - NOT kitten food which has very high protein). The best thing is more water in her diet as it'll help flush out her kidneys better. I'd gruel down the canned food with 2-3X extra water so she will drink more. She may be meowing for more water content!

[Kimberly Coyner, D.V.M., DACVD]

I would also have your veterinarian check her thyroid panel, as hyperthyroidism can cause increased hunger and weight loss in older cats.