What it is
Fat is more than a store of energy: fatty tissue affects hormones and metabolism, so a large amount of it changes how the body handles sugar and how the joints feel. The heavier a cat gets, the less it wants to move, and the less it moves, the easier it is for the weight to keep climbing.
Weight can creep up so slowly that someone who sees the cat every day does not notice. Check with your hands: in a cat at a healthy weight the ribs can be felt under a thin layer, and from above there is a waist behind them.
A heavy cat finds it harder to wash its back and the base of its tail, so the fur there may mat or turn greasy. That change, too, is a sign worth discussing with a vet.
Signs you may notice
The ribs are hard to feel through a layer of fat, there is no waist when you look from above, and the cat moves less, tires sooner and struggles to jump up.
When to see a vet
Book a visit if your cat has put on weight, moves with more effort or no longer keeps its coat clean. A vet will assess its body condition.
For everyday care
These are everyday care products, not a treatment. Ask your vet before changing your cat's food.
How much should my cat eat? Feeding calculator A daily amount by weight and body condition; for an overweight pet it is worked out for the target weight.This is general information, not veterinary advice. For your own cat's health, tests and treatment, see a vet.