A cat dubbed the world’s fattest feline has died despite a stint at pet fat camp.

Crumbs, an online sensation who weighed 38 pounds, had lost seven pounds at the veterinary weight-loss centre in Perm, Russia, but developed breathing problems and died.

Vets blamed his extensive rolls of flab for hiding the cancerous tumours that are suspected to have killed Crumbs, known as Kroshik in Russian, on Saturday. Scans had failed to detect them.

Images of the cat went viral after he was rescued from a hospital basement, where he was raised on scraps, soup and biscuits.

Known as the world’s fattest cat, he was too heavy to walk.  At the fat camp he was put on a strict diet and exercise regime, including walking on an underwater treadmill.