Obesity in dogs is a prominent issue worldwide with approximately half of all companion dogs estimated to be overweight. Obesity poses serious welfare concerns, predisposing dogs to many diseases as well as leading to a poorer quality of life and shorter lifespan.
An online survey conducted in the United Kingdom analysed the link between obesity and behaviour problems in dogs, as reported by their owners. The survey was carried out in conjunction with a four-part television documentary series “Dogs – Their Secret Lives”, which explored dog health, behaviour and welfare. Dog owners wishing to take part in the study were able to complete the survey online through the Channel 4 website.
The survey consisted of 43 questions and included details about the dogs age, sex, breed, neuter status, body weight, behaviour, and more. The data collected comprised 11,154 dogs of which 6220 were male and 4935 were female, and consisted of over 80 different breeds.
The results showed a correlation between obesity and undesirable behaviours, including guarding and stealing food, aggression, fear of going for walks, and poor recall. The authors identify the link between obesity and food related behaviour problems as being the most logical of the findings given they share common risk factors. For example, dogs with strong food drives are inherently more likely overeat and to display food related behaviour issues.
The authors suggest the correlation between overweight dogs and tendency to display signs of aggression, fear when out walking, and poor recall could be due to owners being less likely to exercise their dog, or a restriction of freedom when out walking. This theory is supported by the current study which did indeed find that dogs who exhibited these behaviours are less likely to be let off the lead while being walked.
It was also found that owners of overweight dogs tended to have a different ownership style and relationship with their dog than the owners of dogs not considered overweight. Specifically, they were more likely to perceive them as a “baby” and tended to allow them to sleep in or on their bed, which could also partly contribute to behaviour issues.
This study has several limitations, most notably, a surprisingly low 16.1% (1801) of dogs were reported by their owners to be overweight, contrasting with current estimates that between 30-60% of dogs in the UK are overweight. This discrepancy may be due to a reluctance of owners of overweight dogs to participate in the study, or it may simply be that owners are not aware of the true body condition status of their dog. Future studies should consider the use of a validated body condition scoring system undertaken by a veterinary professional to avoid this potential bias.
As this survey was carried out in collaboration with a television series which directly explored the health, behaviour, and welfare of dogs, this may have resulted in a response bias from participants, whether consciously or unconsciously, adapting their opinions after having watched the television show.
This research suggests a link between obesity and the presence of certain behaviour problems in dogs, however more research is required to conclusively demonstrate this relationship given the limitations identified.
The full article is available here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5468744/
German, A., Blackwell, E., Evans, M. and Westgarth, C. (2017). Overweight dogs are more likely to display undesirable behaviours: results of a large online survey of dog owners in the UK. Journal of Nutritional Science, 6, doi:10.1017/jns.2017.5.
 The Kennel Club Limited. (2018). ‘The Facts on Dog Obesity’. Available at: https://www.thekennelclub.org.uk/activities/get-fit-with-fido/the-facts-on-dog-obesity/ [Accessed 31 Jan. 2018].