Small Animals & Exotic JAVMA | JUL 15, 2019 | VOL 255 | NO. 2 205 L ittle information is available in the scientific lit- erature regarding the changes in BW of cats over their lifetimes and the relationship of BW with breed and sex. 1 Obesity is a growing concern in the human population as well as in many nonhuman animal spe- cies in contact with people, including domestic cats. 2 In people, weight gain during early adulthood was as- sociated with decreased odds of healthy aging, with an increase of ≥ 2.3 to < 10 kg (5 to 22 lb) associated with an increased risk of developing chronic diseases such as diabetes, hypertension, and cardiovascular disease. 3 Investigation of relationships between body weight and age among domestic cats stratified by breed and sex Adam J. Campigotto DVM Zvonimir Poljak DVM, PhD Elizabeth A. Stone DVM, MS Deborah Stacey PhD Theresa M. Bernardo DVM, MSC From the Departments of Population Medicine (Campigotto, Poljak, Bernardo) and Clinical Studies (Stone), Ontario Veterinary College, and the De- partment of Computer Science (Stacey), University of Guelph, Guelph, ON N1G 2W1, Canada. Address correspondence to Dr. Campigotto (acampigo@ uoguelph.ca). OBJECTIVE To evaluate mean body weight (BW) over the lifespan of domestic cats stratified by breed and sex (including reproductive status [neutered vs sex- ually intact]). ANIMALS 19,015,888 cats. PROCEDURES Electronic medical records from veterinary clinics in the United States and Canada from 1981 to 2016 were collected through links to practice manage- ment software programs and anonymized. Age, breed, sex and reproduc- tive status, and BW measurements and measurement dates were recorded. Data were cleaned, and descriptive statistics were determined. Linear re- gression models were created with data for 8-year-old domestic shorthair, medium hair, and longhair (SML) cats to explore changes in BW over 3 decades (represented by the years 1995, 2005, and 2015). RESULTS 9,886,899 of 19,015,888 (52%) cats had only 1 BW on record. Mean BW for cats of the 4 most common recognized breeds (Siamese, Persian, Hi- malayan, and Maine Coon Cat) peaked between 6 and 10 years of age and then declined. Mean BW of SML cats peaked at 8 years and was subjectively higher for neutered than for sexually intact cats. Mean BW of neutered 8-year-old SML cats increased between 1995 and 2005 but was steady be- tween 2005 and 2015. CONCLUSIONS AND CLINICAL RELEVANCE The large dataset for this study yielded useful information on mean BW over the lifespan of domestic cats. This could be a basis for BW manage- ment discussions during veterinary visits. A low frequency of repeated BW measurements suggested a low frequency of repeated veterinary visits, especially after 1 year of age, making engagement of cat owners in the health of their animals particularly relevant. ( J Am Vet Med Assoc 2019;255:205–212) Although ideal BWs for cats of different breeds and sexes have not been established, short-term stud- ies 4–6 that involved 118 to 14,270 cats have estimated the prevalence of obesity in cats in the United States to range from 27% to 39%. Obesity has been associ- ated with arthritis, diabetes mellitus, cardiac disease, respiratory illness, and other diseases in cats. 7 Re- search has shown that cats have a decreased ability to digest proteins, fats, and starches as they age, 8 and weight loss, particularly in older cats, 9 has been ob- served with diseases such as hyperthyroidism, renal disease, and neoplasia. 10–12 Currently, veterinarians have limited resources available to determine an ap- propriate target BW for different cat breeds. The ob- jective of the study reported here was to characterize BW changes over the lifespan of domestic cats and in- ABBREVIATIONS BCS Body condition score BW Body weight CI Confidence interval SML Shorthair, medium hair, and longhair