To determine the association between body condition and disease in cats.

Prospective study.

Information on 1,457 cats without major illnesses from 27 veterinary hospitals in the northeastern United States.

Cats that had body conditions determined from 1991 to 1992, using a set of 6 body condition silhouettes, had their health experiences and body conditions assessed for the subsequent 4.5 years. Cats were described by the following 6 body conditions: cachectic, lean, optimally lean, optimal weight, heavy, and obese. Data obtained from medical records and owner interviews were collected, using standard forms. Associations between body condition and specific diseases were analyzed. Findings in cats with body conditions other than optimal were compared with findings in cats with optimal body condition.

Compared with optimal weight cats, heavy cats were 2.9 times as likely to be taken to veterinarians because of lameness not associated with cat bite abscesses. Obese cats were also 3.9 times as likely to develop diabetes mellitus, 2.3 times as likely to develop nonallergic skin conditions, and 4.9 times as likely to develop lameness requiring veterinary care. Cats considered thin (cachectic and lean) were 1.7 times as likely to be presented to veterinary hospitals for diarrhea.

Results of this study substantiate reports of health risks associated with excess body weight in cats. Efforts to reduce weight in heavy and obese cats can lead to reduced risks of diabetes mellitus, lameness (presumably related to osteoarthritis and soft-tissue injuries), and skin problems unrelated to allergies. Cachectic and lean cats are more likely to have diarrhea that is not associated with a definitive diagnosis. ( J Am Vet Med Assoc 1998;212: 1725–1731)