Background: Canine obesity is a complex disease affected by genetic, endocrine and environmental factors. It is associated with reduced lifespan and many comorbidities. Prevalence differs by breed, with Labrador retrievers at high risk. Past data on how biological risk factors impact weight gain have been contradictory, possibly because they were obtained from genetically heterogeneous populations. Methods: We investigated risk factors for canine obesity in a population of British Labrador retrievers (n = 521) with high‐quality data on obesity, weight, owner‐reported food motivation and related characteristics. We used linear regression to assess known and novel risk factors for obesity. Results: We found that neutering increased obesity in males (p < 0.001) but not females (p = 0.37). Older age was associated with obesity in female Labradors (p = 0.013) but not males (p = 0.49). We identified two new risk factors for obesity in Labrador retrievers: chocolate coat colour (p < 0.001) and high food motivation (p < 0.001). Limitations: Strategic recruitment to collect both obese and lean dogs means this cohort is not suitable for assessing obesity prevalence in UK Labrador retrievers. Conclusion: Studying this genetically homogeneous population informs our knowledge of common risk factors for obesity and expands those relevant to Labrador retrievers.