Some cats get so fat they can't groom themselves and have to be anaesthetised and groomed by a vet nurse.
Vets on Carlton vet nurse Abbie Ratcliffe sometimes gets the job. She's also taken on the challenge of running a "biggest loser" competition for fat pets as part of a marketing drive for a new pet food.
She said short-haired cats should never need grooming but some of the biggest did.
"They can get mats on their backs and can't turn around and lick themselves."
Overweight cats tended to be grumpy. They could lash out and were anaesthetised before being groomed. An overweight dog was no better.