From the Editors of The Daily Cat
First, make sure you are weighing your cat correctly on the scale. An easy method is to simply step on a scale by yourself and note your own weight. Then pick up your cat and step on the scale. Subtract your weight from the total to get a rough estimate of your cat’s weight. If your cat gains or loses just half a pound in a week, that can be cause for concern.
Your cat is in his senior years, so his body is likely undergoing many changes in terms of muscle mass and other internal processes. This could explain the “bony” feel without actual weight loss. However, a change in body feel can be linked to cancer and other serious illnesses, so it’s crucial to take your cat to your veterinarian for a complete examination.
Your cat’s change in behavior is concerning as well. Cats can’t yell “stop it” when they feel pain, so his biting could indicate that he is feeling some discomfort when you touch him. Consult your veterinarian, who can examine these issues and rule out health problems that could be the cause of all of the symptoms you describe.