A recent study conducted in collaboration with the Alliance for Contraception in Cats & Dogs (ACC&D) and published in the Journal of the American Veterinary Medical Association (JAVMA) offers new insights into the relationship between sterilization practices and obesity risk in dogs. The findings suggest that both breed and the timing of sterilization may play a role in a dog’s likelihood of becoming overweight or obese.

Elective sterilization has long been associated with health benefits, such as a reduced risk of pyometra in females and testicular tumors in males. However, emerging data indicates that sterilization may also influence weight gain in ways that vary by breed and age at the time of surgery.

This multi-institutional research effort included experts from Mars Veterinary Health (including Banfield Pet Hospital), Virginia-Maryland College of Veterinary Medicine, University of California–Los Angeles, Hunter College, and the University of Padova. The team analyzed anonymized health records from over 100,000 dogs across a six-year period. Fifteen breeds were included in the study—five large breeds (26,369 dogs) and ten toy/small breeds (90,002 dogs).

Among the breeds studied, intact Labrador Retrievers, Golden Retrievers, and Pugs were found to have the highest baseline rates of overweight and obesity. In smaller breeds, sterilization at three or six months of age (before puberty) appeared to carry a lower risk of obesity than surgeries performed at one year or older. In large breeds, the outcomes varied more significantly, depending on the specific breed.

The study highlights the importance of considering individual breed traits and timing when making sterilization decisions. These findings may help veterinary professionals tailor advice and care plans more closely to each dog’s characteristics, rather than following a one-size-fits-all approach. Conversations about sterilization can now be better informed by breed-specific data, with an eye toward maintaining a healthy weight and overall quality of life.

“Sterilization has historically been more of a one-size-fits-all approach, and that may still be appropriate in some situations, but our research reinforces the need for customized recommendations whenever appropriate, especially for dogs with risk factors,” said co-author JoAnn Morrison, DVM, MS, DACVIM director of Global Veterinary Science and Health Outcomes at Mars Veterinary Health. “This latest study contributes to a body of knowledge that can help inform more individualized recommendations for surgery timing and proactive strategies around diet and exercise—all while balancing the broader context and importance of population-level benefits.”