Risk factors for underweight and overweight in cats in metropolitan Sydney, Australia

Obesity is regarded as one of the most significant welfare issues in companion animals. Some risk factors affecting body condition in cats have been determined, but many remain controversial. The current study aimed to investigate the risk factors for overweight and underweight in cats in metropolitan Sydney. Electronic patient records for 11 years (2005-2015) were acquired from a feline primary practice in metropolitan Sydney. The 9-point body condition score (BCS) evaluation in each visit was classified into three groups: underweight (1-3), ideal-weight (4-6) and overweight (7-9). Multinomial logistic regression was used to identify the risk factors for underweight and overweight. The risk factors tested included: breed, hair length, sex, neuter status, age at neutering, age at visit, microchip status, lifestyle, reason for the clinic visit and the number of visits by a cat in a calendar year. The BCS examiner was included as a confounder. Over the 11-year period, 4,020 cats had made 18,349 visits to the clinic, from which BCS records were available for 15,659 visits (85.3%), with 834 cats (5.3%) being underweight, 12,362 (79.0%) being ideal-weight and 2,463 (15.7%) being overweight. Although various cat breeds showed a different tendency for body condition, British Shorthair and mixed-breed cats were more likely to be overweight. Non-illness related visits and middle age (7-11 years old) were also risk factors for overweight. The risk factors for underweight included purebred cats (apart from British Shorthair and Burmese), medium-or-long hair, being intact, increase in age, not having a microchip and illness-related visits. Sex was not a significant risk factor for either overweight or underweight. The study demonstrated that the risk factors for overweight and the protective factors for underweight were not necessarily the same, highlighting the importance of investigating the risk factors for underweight and overweight separately in future research.