ITHACA, N.Y. -- Seriously overweight cats are more likely to suffer diabetes mellitus, lameness and non-allergic skin conditions, a Cornell University veterinarian's four-year follow-up to a feline obesity study has shown.
Most likely to be tubby are neutered, apartment-dwelling, mixed breed cats eating prescription cat food.
"The original obesity study and the follow-up confirm what veterinarians and cat owners have suspected for a long time," said Janet M. Scarlett, D.V.M., associate professor of epidemiology in Cornell's College of Veterinary Medicine. "Too much extra weight is not healthy for the cats, but being very thin can be a problem, too."
Scarlett was a collaborator, along with veterinary nutritionist Susan Donoghue, in the landmark 1989 study of 2,000 cats at 31 veterinary clinics in the Northeast, as well as the principal investigator of the tracking study. The Waltham Centre for Pet Nutrition in the United Kingdom funded the first study, which found that about 25 percent of cats brought to veterinarians are overweight: 20 percent were ranked as "heavy" by veterinarians and 5 percent were considered "obese." Slightly more pet owners -- about 29 percent -- thought their cats were overweight in the same survey.
Ralston Purina Co., the American pet food manufacturer, funded the four-year follow-up, in which Cornell veterinary students called as many of the original pet owners as they could locate and asked about the cats' health. Researchers also reviewed veterinarians' medical records for the animals in the first survey. Among the findings:
Veterinarians in the survey ranked the cats, from extremely thin to optimal to obese, after physically examining the cats' body condition under their fur and comparing the cats to a series of six standard silhouettes.
Unlike the case with humans, there is no body-mass index for obesity in cats, Scarlett noted.
Most cats refuse to sit still for the electrical impedance test -- one way to measure body mass -- and they really dislike the other method -- being completely immersed in water while exhaling. Ranking body condition by silhouettes is currently the most practical way to survey large numbers of privately owned cats, the epidemiologist said.
In the original study, cat owners completed a three-page survey with information about their animals' breed, housing accommodations and lifestyle, food, age, gender, whether the animal was neutered and other factors that could affect body condition. Analysis of those reports found several factors that are associated with being overweight:
The veterinarians were surprised to find cats putting on extra weight so early in life. By one year of age, some 15 percent of cats in the survey were already overweight. And by two years of age, nearly 20 percent had landed in the "heavy" or "obese" categories.
Results of the 2,000-cat obesity study were reported in the International Journal of Obesity (Vol. 18 Supplement 1, 1994). Results of the follow-up study will be presented at the Eighth Symposium of the International Society for Veterinary Epidemiology and Economics July 8-11 in Paris.
Tips for cat weight-watchers
James R. Richards, D.V.M.
Director, Feline Health Center, College of Veterinary Medicine, Cornell University