Jeremy Clarkson’s pot belly, as is the case for most men, is probably caused by a liking for wine or beer. However for domestic cats a distinct pot belly as opposed to signs of obesity is likely to be due to fluid in the abdomen which is called ‘ascites‘.
It is caused by liver, heart or kidney disease. Therefore the appearance of a pot belly is cause for a veterinarian visit asap.
Asites can also be caused by increased pressure in the veins of the abdomen. As for liver disease it is the result of decreased protein synthesis by the liver. Fluid leeks out of the blood vessels.
Feline infectious peritonitis (FIP) is the most common cause of ascites. This is a nasty killer disease. The reason why it causes a pot belly is because the virus acts on capillary blood vessels in the cat’s body particularly those in the abdomen (and eyes, brain and lymph nodes for example). The virus damages the tiny blood vessels leading to a leek of fluid from the vessels into the body cavity and tissues where it forms the pot belly.
So if you ask “why does my cat have a pot belly?” you probably should be concerned and take your cat to your veterinarian for a check up particularly if your cat has interacted closely and continuously with other cats because FIP is transmitted from cat to cat.
Sources: PoC (earlier articles).