We had two cats, one 16 (a rescue) and one 12 (Scottish Fold). The 16-year-old cat passed away, and the 12-year-old has become very vocal and lost weight (previously overweight). I don't suspect kidney disease or pain. It is more like an attention-getting meow. The vet switched her to hypoallergenic food, and I'm wondering if this could be causing her weight loss. She used to eat the other cat's food and now only eats her own. Does she need a new playmate?
Cats can be very social creatures and often form deep attachments to members of their family, whether human, feline or other animal. It is normal for cats to grieve when a loved one dies, and they can show this grief in many different ways. Weight loss and vocalizing can also be symptoms of an underlying medical issue, especially considering the age of your kitty. She should be seen by a veterinarian for a complete physical exam, lab work and blood pressure measurement. A hypoallergenic food shouldn't cause weight loss unless she is not eating enough. If she doesn't like the food, your veterinarian can recommend another one.