"The relationship between Irish owners and their cats has changed entirely in the last 20 years, " said vet Pete Wedderburn. "Before, cats tended to be working cats and had a purpose, such as catching mice.

Now they are viewed more as companions and many people devote a huge amount of time and energy to keeping them happy."

This has led to owners misguidedly keeping their cats indoors at all times to protect them from traffic and cat fights and indulging them constantly with their favourite food.

"Owners get a great deal of pleasure out of watching their cats eating happily and they feed them with so many tasty treats that the cats go against their basic instinct and eat more than they should, " said Wedderburn. "As a result, cat obesity is becoming more and more common over here and that is a problem."

Although protective cat owners prefer to keep their pets indoors at all times to protect them from the elements, Mark Beazely of the ISPCA believes there needs to be more of a balance to help keep cats healthy.

"We believe that keeping a cat inside at all times is not healthy for the cat or for the owner, " he said. "Instead, there should be a good mix of outdoor activity and indoor. A cat flap can often be the answer to this kind of problem."

A UK-wide study of diabetes among cats in Britain found last week that one in 230 cats suffers from the disease as a direct result of obesity. In the United States, where feline diabetes has increased fivefold in the last 30 years, cat yoga classes have become de rigueur for overweight felines. While Ireland has not yet reached such high levels of feline diabetes, vets and animal protection workers are becoming increasingly concerned about overweight Irish cats.

"I would recommend that owners keep a close eye on their cat, and if they are concerned, take them to the vet to have them weighed, " said Wedderburn, who has come across cats weighing up to 10kg (22 lbs).

"Playing with your cat and keeping them fit with a scratching post or indoor gym are also great for keeping cats active."

Indoor gyms have become a hit with Irish cat owners in recent years, with ceiling-high gyms being some of the most popular, according to Lindsey Kenny of Pet Bliss Ireland.

"They become almost a part of the furniture and don't take up much room, " she said. "Cats love them because they have dangling strings to play with and hammocks to sleep in. It certainly helps to keep them fit."