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Association between life span and body condition in neutered dogs | VETgirl Veterinary Continuing Education Podcasts

How many of us dread having “the talk” with clients? That one where you brace yourself for the response you know these words are going to elicit from the client across you… “Your pet is obese.” Perhaps an angry client reaction is brought about out of shame for letting their pet get fat, or from the implication that their shower of love and affection in the form of kibble and treats is slowly killing their beloved pet. This is undeniably a tricky conversation to have with owners, but it is a real concern for our patient’s overall health. We can tell owners that by allowing their pets to remain obese, they are increasing their pet’s risk for CCL rupture (Adams), arthritis (Yamka), diabetes mellitus, and cancer (Lund). These diseases seem so elusive and far-off to the pet parent paying more attention to their cute puppy dancing around the room than to your education. But what if you were to tell the client that obesity will shorten their pet’s lifespan and the time they have left with their pet? Studies under controlled conditions have already documented this relationship between a longer lifespan derived from limited volumes of food in a colony of Labrador Retrievers (Kealy).

So, in today’s VETGirl podcast, we review a study by Salt et al entitled Association between life span and body condition in neutered client-owned dogs. This is a retrospective study and the first to be conducted in the real-world setting of client-owned dogs and documented in many breeds. The authors wanted to evaluate the affect obesity has on the lifespan of neutered, client-owned dogs. Medical records from dogs among the 12 most common breeds, spanning from Chihuahuas to German Shepherds, were evaluated in this study. Since obesity is often a gradual development over a dog’s lifespan, the authors chose to limit the data they reviewed to only the clinic visits occurring between 6.5 and 8.5 years of age.

We often talk about body condition scores, or BCS, in our patients, but remember the BCS scoring system is a relatively new classification that came about in 2010. Before the BCS system, we had a 3-category classification scheme of “thin”, “normal”, or “heavy.” So to standardize analysis of the records since they contained a mix of both scoring systems, the authors re-assigned the dogs classified by the BCS system into the 3-category scheme as follows: Dogs classified as BCS 1 and 2 were grouped into the “thin” category, BCS 3 became the “normal” category, and dogs in BCS 4 and 5 were grouped into the “heavy” category. Now, how many times have you and your colleagues disagreed on a patient’s classification as a BCS 3 or a 4? Even though we have guidelines like whether ribs are visible versus only palpable, it’s easy to have pets fall into a grey zone and be classified differently depending on the attending clinician. Or sometimes we forget to assign a BCS to our patients and the computer may enter a default code when we leave it blank. To help mitigate some of these inconsistencies, the investigators did their best to read through records and determine whether the body condition classification of the patient seemed to be appropriate. So, as an example, if a BCS 3 was assigned in the medical record, but the associated physical exam said that the dog was so fat he waddled into the exam room or his body weight didn’t reflect his breed standard even remotely, the authors did their best to reassign the body conditions to reflect their described physical stature despite the conflicting BCS score found in the record.

So what did the authors find in this study? Median survival times were found to be shorter for overweight dogs of all 12 breeds studied. What is really interesting is that they also found another neat little trend. For larger dogs, obesity had less of an impact on survival times compared to smaller obese dogs. German shepherds represented the largest dogs in the breed studied and their survival time was shortened by a median of 5 months, whereas male Yorkshire terriers had a decrease in 2 years due to their obesity. VETGirl wonders if this difference in survival times could be related to common secondary diseases that come about in the different breeds as a result of their obesity. Things like diabetes mellitus are a more common obesity-related disease in little dogs, whereas osteoarthritis is a more common large breed dog disease. Now, arthritis certainly can drastically impact quality of life, but perhaps DM is a bit more difficult to manage from both the medical aspect and the client aspect. Or maybe this relationship has something to do with the relative trend we see in larger breeds having an overall shorter lifespan than the smaller breeds? Who knows at this point. The reason is still open. BUT, let’s get back to the focus of this study. Say it with me! “Obese dogs have a shortened lifespan!” What a truly profound finding in our client-owned dogs! And now we have the evidence in veterinary literature to back it up.

Even though this study only evaluated 12 breeds, ALL 12 breeds exhibited the same trend in shortened lifespans owing to an increase in body condition. So this relationship is likely true for all dogs of any breed or mixed breeds. Future studies may be able to elicit how or why obesity shortens a dog’s lifespan. We guess it’s likely related to either the more rapid development of systemic diseases brought on by obesity (e.g., neoplasia, endocrinopathies, orthopedic disease) – but whether it makes these diseases more difficult to manage, makes their progression accelerate, or causes a decreased quality of life or unmanageable management for pet owners, remains unclear. There is likely also a biochemical reason for this trend. Insulin is one of the biomarkers studied in obesity and they’ve found that insulin levels were lower in animals fed restricted portions. This is another area that is being studied and will likely be elaborated on in the near future.

Let’s talk about some of the strengths and limitations of this study. Often in veterinary studies, we are limited by numbers of pets meeting our inclusion criteria. Sample size is certainly this study’s strength! 50,787 dogs were evaluated in this study. That’s huge! But those numbers typically are only found in retrospective studies. Sometimes the information in retrospective studies can’t be validated or information is missing from the medical records or incorrect, and so retrospective studies can be seen as a limitation. Body condition assignments were made by many different clinicians in this study and so there may be differences between what I think is a BCS 4 and what you think is a BCS 3. The authors chose to categorize the dogs’ body conditions reflected at only one time point in their life. They chose a typical “mid-life” timepoint to be reflective of their body condition throughout their lifespan, but it’s unclear whether the pets remained that condition the majority of their life or whether these animals hit the dog parks and conditioned back to a normal weight. If these animals did become more svelte or were svelte and then became obese outside the time point selected for the body condition assignment, then their data could have influenced the lifespan evaluation portion of this study. The number of pets that drastically changed in body condition is likely small, and since there are so many pets included in this study, these uncommon changes were likely diluted and imparting little effect on the lifespan evaluation portion. And finally, over the large time range of this study we have had big changes in nutrition advances and medical advances that influence pet’s lives and could be imparting longevity to the dogs in the end of the study timeframe.

So, what do we take away from this VETgirl podcast? Even though there are a few limitations to this study, the sheer numbers used make it possible to say that there truly is an association between obesity and shortened lifespan in neutered pets. We can’t say that “obesity kills pets,” because that kind of relationship is a bit trickier to statistically prove, but we can absolutely tell clients that if their pet remains a healthy weight, he is likely to live longer. I know this is a study I’m going to keep at hand to help my clients appreciate the seriousness of pet nutrition. Skinnier saves, and let’s make sure to educate our pet owners that love shouldn’t be shown by feeding more treats, but by keeping our veterinary patients trimmer.

References:
Adams P, Bolus R, Middleton S, Moores AP, et al. Influence of signalment on developing cranial cruciate rupture in dogs in the UK. J Small An Pract 2011;52(7):347-352.

Yamka RM, Friesen KG, Frantz NZ. Identification of Canine Markers Related to Obesity and the Effects of Weight Loss on the Markers of Interest. Intern J Appl Res Vet Med 2006;4:282-292.

Lund EM, Armstrong PJ, Kirk CA, Klausner JS. Prevalence and risk fac- tors for obesity in adult dogs from private US veterinary practices. Int J Appl Res Vet Med. 2006;4:177-186.

Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction on life span and age-related changes in dogs. J Am Vet Med Assoc 2002;220:1315-1320.

Salt C, Morris PJ, Wilson D, et al. Association between life span and body condition in neutered client-owned dogs. J Vet Intern Med 2019;33:89–99.

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