Fat cats? New study shows cats' heaviest weight higher now than in 1990s

A new study involving more than 19 million cats from across Canada and the United States suggests most of the animals continue to put on weight after they reach adulthood, and their heaviest weight is higher now than it was two decades ago.

Researchers at the Ontario Veterinary College at the University of Guelph analyzed 54 million weight measurements taken at vet offices between 1981 and mid-2016 to get a sense of the typical weight gain and loss pattern over the course of a cat's life.

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They say the study, published in the Journal of the American Veterinary Medical Association this week, is the first of its kind to use such a large pool of data.

Overall, the data showed cats' mean weight reached its peak between six and 10 years of age for the most common purebred breeds — Siamese, Persian, Himalayan and Maine Coon — and at eight for domestic cats.

Male cats generally hit higher weight peaks than female cats, and cats that were spayed or neutered tended to be heavier than those that weren't.

The findings showed a difference of about one kilogram between age one and the peak. As well, the mean weight of neutered, eight-year-old domestic cats rose about 1/4 of a kilogram between 1995 and 2005 and then remained steady for the next decade.

"It might not seem like much but half a pound is still a significant amount for a cat," said lead author Adam Campigotto.

The study is meant as a starting point for further research and did not look at what caused the changes in weight, nor did it establish what a healthy weight is, said Campigotto.

Some possible, untested explanations for the shift include that more people may have begun to keep their cats indoors in that time period, or that changes were made to the palatability of cat food, or in pet owners' feeding behaviours, he said.

"Treats can have a big impact on weight for their animals and often people associate giving treats as a kind of love," he said.

The researchers said slightly more than half the cats involved in the study had only one weight measurement in their veterinary file, which they said suggests the animals' owners may not have scheduled regular vet visits or may have switched clinics.

However, the sheer number of records collected meant researchers were able to fill those gaps by combining all values for each year of age, the team said.

Another of the study's authors, Theresa Bernardo, who is also a professor at the college, said pet owners may want to begin weighing their cats at home if it isn't being done at the vet. Weight changes may be linked to other health issues, though those correlations were not drawn in this study, she said.

One of the next steps will be to look at how to manage cats' weight, Bernardo said.

"We have another project where we're looking at using technology like automated feeders," she said.

"In many cases, there are multi-cat households and sometimes one cat is eating a good share of the other cat's dinner, so there are feeders now that will actually feed each cat separately, which helps you get a hold of that kind of situation."

The study's findings can help vets discuss health issues related to weight with cat owners, the researchers said. More work is needed to explore the links between cats' body weight and various conditions, they said.

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