In 2021, some in the veterinary community seemed to finally acknowledge that spay and neuter are top risk factors for weight gain in dogs.²⁰⁵ Spayed and neutered dogs have a higher risk of weight gain for two simple reasons:

1. Their metabolism slows down²⁰⁶
2. Their appetite goes up²⁰⁶

Changes to metabolism and appetite can begin as early as three days post procedure.

These recent findings are consistent with previous canine obesity^30,31,32 studies and the interim findings in the Golden Retriever Lifetime Study (GRLS). At the Aug 21, 2018 Fetch dvm360 conference in Kansas City, Missy Simpson, DVM, PhD, epidemiologist for the Morris Animal Foundation’s GRLS presented. Dr. Simpson reported that compared to intact dogs, dogs that underwent gonadectomy (spay or neuter) when they were 1 year old or younger faced a two-times higher risk for overweight or obesity. Dogs older than 1 year had a 40% increased risk for overweight or obesity. Further, Dr. Simpson shared that for every year older the dog was when gonadectomy occurred, it reduced the risk of overweight and obesity by 70%.

We were pleased to see the GRLS provide data that correctly identifies spay/neuter as an underlying cause of the rise in canine obesity. However, we found international studies in 1986 and 2005, and a US study in 2006 which had similar conclusions . Again, in 2013 researchers at UC Davis pinpointed spay/neuter as a cause of metabolic change and weight gain as well as serious orthopedic conditions and cancer in dogs. We found their explanation to be so clear and definitive, we have featured an article about the study on its own web page, “The Smoking Gun“.

Yet the veterinary community and associated organizations often still continue to associate many adverse conditions with obesity, without acknowledging that the cause of obesity may in large part be early spay or neuter. For example, the Association for Pet Obesity Prevention (APOP) conducts an annual Pet Obesity Awareness Day and invites pet guardians and vets alike to participate in their effort to assess the actual percentage of the pet population that is obese, as pet obesity in the U.S. continues to increase. In 2018, an estimated 55.8% of dogs were considered overweight or obese. The APOP lists the following as the “Primary Risks of Excess Weight in Pets”:

• Osteoarthritis
• Insulin Resistance and Type 2 Diabetes
• High Blood Pressure
• Heart and Respiratory Disease
• Cranial Cruciate Ligament Injury
• Kidney Disease
• Many Forms of Cancer
• Decreased life expectancy (up to 2.5 years)

Nationwide, a leading pet insurer, reveals that pet obesity is on the rise for the sixth straight year; rising by 23 percent over the last three years. Nationwide’s list of the 10 most common obesity-related conditions in dogs is:

• Osteoarthritis
• Bladder/urinary tract disease
• Low Thyroid Hormone Production
• Liver Disease
• Torn Knee Ligaments
• Diabetes
• Diseased Disc in the Spine
• Chronic Kidney Disease
• Heart Failure
• Fatty Growths

Dr. Carol McConnell, DVM, MBA, vice president and chief veterinary medical officer for Nationwide recommends pet guardians initiate “regular exercise routines for our pets and begin to effectively manage their eating habits to avoid excess weight gain.”

Dr. McConnell’s advice seems on the surface to be reasonable, but her omission of the findings of current research with respect to obesity is unconscionable. Millions of dogs are being fed smaller and smaller portions of kibble, without the desired result. The veterinary profession has failed to provide meaningful information for the pet guardian. The scientific evidence for an association between obesity and all of the health conditions on these two lists is very strong. However, the information we need as pet guardians is the answers to the following questions; does obesity “cause” all those health problems, or does it just make them worse? Will keeping my dog at an optimal weight prevent them from experiencing any or all of these health problems?

Our dog Billy suffered from the vast majority of the conditions listed by the two aforementioned organizations as being related to obesity. Yet he was never overweight, much less obese. As an example, Billy tore ligaments in both of his knees, and this health problem appears on both lists. Having made many visits to the orthopedic surgeon’s office, we saw young, active dogs who were fit and at a normal weight presenting with knee ligament tears, not obese sedentary dogs. Were all these dogs an exception? Looking at our webpage entitled “Cranial Cruciate Ligament Tear” you will see that many studies can scientifically explain the mechanism by which early spay/neuter causes this orthopedic problem. Although obesity is often associated with a myriad of orthopedic problems,  obesity alone would never cause a bone to grow too long, creating an excessive TPA – the underlying cause of most cranial cruciate ligament tears. Perhaps the veterinary community has failed for such a long time to come to consensus that obesity is directly related to spay/neuter because they have no explanation as to why spay/neuter causes obesity. The studies have generally been observational. If you acknowledge that spay/neuter is an extremely efficient endocrine disruptor, you can begin to understand and explain the correlation between spay/neuter, obesity and even the increase in canine diabetes.

We believe we can utilize the “Canine-Human Connection” model and current research for both species to understand and ultimately overcome the problems associated with obesity in both humans and dogs. The recent dramatic rise in obesity rates in humans is an alarming global health trend. Not only does it consume an ever increasing portion of health care budgets in Western countries, but it affects each and every one of our daily lives in some fashion. The cause of obesity has long been thought to be the prolonged consumption of more caloric energy than is needed for the energy exerted with physical activity. Hence, the major focus of preventative programs for obesity has been to target overeating and inadequate physical exercise.¹²⁵  Likewise, our canine companions are experiencing an increase in obesity, and the traditional solutions are not effective for most.

It is of particular concern that the incidence of both obesity and diabetes are rising rapidly in the young. There can be no argument that eating calorie-dense, nutrient-poor food in large portions plays an important role,¹²⁴ and perhaps that can explain in part the rise in obesity among our youth. However, the fact that young people are rapidly being diagnosed with Type 2 diabetes has raised concerns throughout the medical community. If one were to examine a medical textbook from 30 years ago, they would see that Type 2 diabetes was termed adult-onset diabetes. Why is Type 2 diabetes now also afflicting the young, and in alarming numbers? Likewise, fifteen years ago veterinarians told us dogs were not subject to Type 2 diabetes. If you have read our website’s section regarding diabetes, you will see that type 2 diabetes is now diagnosed in dogs and has increased almost 80% in the last ten years.

Globally, emerging evidence ties endocrine-disrupting chemical (EDC) exposure to obesity and diabetes, according to the executive summary of a Scientific Statement issued by the Endocrine Society. While the precise metabolic pathways targeted by most of these chemicals are uncertain at present, the data linking EDCs with obesity, metabolic syndrome and diabetes are strong and the number of studies finding positive association is growing.¹²⁴

Evidence points to endocrine disrupting chemicals that interfere with the body’s adipose (fat) tissue biology, endocrine hormone systems or central hypothalamic-pituitary-adrenal axis as suspects in derailing the homeostatic mechanisms important to weight control.¹²⁵ In simple terms, exposure to endocrine disruptors greatly enhances the probability of one experiencing significant weight problems. In the European Union (EU), obesity and diabetes are epidemic and exposure to endocrine-disrupting chemicals (EDCs) is increasingly recognized as a contributor to obesity, independent of diet and physical activity.¹²⁶ One proposed mechanism of action is the “environmental obesogen hypothesis” which holds that prenatal or early life exposure to certain endocrine disrupting chemicals (much the same as the endocrine disruption caused by early spay/neuter) can predispose exposed individuals to increased fat mass and obesity.¹²⁷

Our dispute with the current information about obesity in our dogs is the failure of the veterinary establishment to acknowledge that endocrine disruption created by spay/neuter can be a major contributing factor in the development of obesity as well as the underlying cause of the health problems vets associate with obesity in dogs. Perhaps vets who have recommended spay and neuter for thousands of dogs over their career cannot bring themselves to admit they have caused irreparable damage to these dogs and that there are NO benefits to endocrine disruption. (View Dr. Becker’s video on this website to see her admission as to how painful it was for her personally when she recognized the harm she had inflicted by recommending and providing spay and neuter procedures).

The Physical Effects of Spay page on this website provides the scientific basis for us to conclude spay not only increases the risk of obesity by a factor of 1.6-2, ^30,31,32  but independently is a causative factor for most, if not all, of the diseases listed here as associated with obesity.

The Physical Effects of Neuter page on this website provides the scientific basis for us to conclude neuter not only triples the risk of obesity,^30,31,32 but independently is a causative factor for most, if not all, of the diseases listed here as associated with obesity. This information can help explain why many dog guardians supervise their spayed or neutered dog’s food intake and exercise closely, yet still battle obesity in their dog. The changes in a dog’s metabolism after spay or neuter may be permanent, but perhaps it is time to provide “hormone balancing” for these dogs and see if we are able to enhance their metabolic rate and depress their voracious appetites. This alone would certainly enhance the quality of life for these dogs, and certainly they would be healthier.

It is our contention, that in the case of spay/neuter, and only in the case of spay/neuter, our best friends can get fat just by looking at food.