Hiya Shani
My take would be take her to the vet. When people are bigger than they wanna be and have problems losing the weight, they go to the doctor to see how to expidite the process- do the same with the cat. Could be the cat just got adolescent fat like us humans do, or perhaps it's got a thyroid condition or something. It's nice that you care- I see so many people with pets that are obviously unhealthy and their owners are oblivious to that fact!
Let us know if the Atkins Kitty Diet works!
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Sage knows our mythic history, King Arthur's and Sir Caradoc's
She answers hard acrostics, has a pretty taste for paradox
She quotes in elegiacs all the crimes of Heliogabalus
In conics she can floor peculiarities parabolous
-C'hi