Reason for concern???

[shakkamommy]

My 15 year old cat has recently begun eating A LOT- like everytime we go to the kitchen. She sits by her dish and when we feed her, eats every bit of the food. However, she's not gaining any wait-at all. Isn't that odd?
Now, a few changes have occurred. I recently came to stay with my mother and brought my dog and new kitten (she's officially my mother's cat so is usually by herself). At first, they would eat any of her food that she didn't finish. I think that explains her eating all of the food each time, but what about the frequency and the non-gaining of weight?
She is still acting happy and fine in all respects. Am I just being overprotective (something I have been accused of in the past with my animals)?
Thank you all for your help!

[Lucky Rescue]

At 15, your cat probably has a throid problem, diabetes etc.

She must go to the vet, get a blood test and be put on appropriate medications.