I will second everybody here, this is mostly happening because you have recently spayed/neutered your cat. Otherwise, I don't really find any reason for which it might have worsened, because you're basically keeping it under "harsh diet". My cats have been always fit, even though I kept giving them a lot of food on a daily basis, and they were basically procrastinating rather than even moving a single paw... I do hope it's not something genetically-related, because that might worsen your cat's condition over time and potentially have some serious issues to deal with afterwards. I've recently seen a video that involved a cat with more than 30 Kg ( ~66 pounds!!!) that couldn't even move its head because the malevolent condition. Could you believe your eyes if you saw it?
