2 Mar 2021
Alex German
Job Title
Figure 1. Use of evidence-based growth chart in a Labrador retriever puppy.
It’s a daunting job for any veterinary professional to pluck up the courage to speak to a client about his or her dog’s weight issues. Since owners want their beloved pet to live as long and as healthy a life as possible, focusing on possible effects of excessive weight on lifespan could have more traction.
This article discusses research that demonstrates an association between overweight body condition and a shorter lifespan in pet dogs from many popular breeds (Salt et al, 2018). The article further highlights the benefits of modest weight loss in dogs that are already overweight, as well as a strategy for prevention in those that are not. It is hoped that implementing such programmes will have a lasting impact by improving both the quality and quantity of life of our four-legged friends.
Your first patient of the day is a middle-aged Labrador retriever that also has concurrent obesity. Whatever the primary reason for presentation, you know you will also need to have a difficult conversation with the owner about their pet’s waistline.
Most vets would confirm it’s a rare client who brings his or her pet to the clinic specifically to discuss a weight issue and, therefore, it’s a daunting job for any clinician to pluck up the courage to talk about it. One paper (Kipperman and German, 2018) highlighted many of the reasons why vets may be willing to not tell a client that his or her pet is overweight, and most of them are likely to resonate with readers.
The difficulties do not end with the dilemma of how to start the conversation since, despite what you might say to them, some clients will not truly engage with the subject. Attempting to change human behaviour is a real challenge, with many elements of psychology involved. Habits are hard to break – especially around food and feeding. Furthermore, it can be difficult to convince some owners that a problem even exists.
Body condition scoring charts can be used to help illustrate the changes in body shape that occur with obesity. However, owners can find it hard to assess their pet’s weight and tend to underestimate how overweight they are (Eastland-Jones et al, 2014). Even if they do acknowledge the problem, it can still be challenging to persuade them of the benefits of getting their pet to a healthy weight.
One option might be to highlight the health risks that a dog or cat with obesity could face – for example, concurrent orthopaedic disease, diabetes mellitus, respiratory conditions or certain cancers (Lund et al, 2006; German et al, 2010).
However, owners are not always engaged by this approach, in much the same way that smokers might not be convinced to stop smoking as a result of the health risks. This is particularly the case where an overweight pet is otherwise apparently healthy.
An alternative approach is to focus on quality of life, given work demonstrating poorer quality of life in dogs that have obesity (German et al, 2012). Such a discussion is all the more compelling, given that most owners see marked improvement in quality of life after successful weight loss.
Since owners want their beloved pet to live as long and as healthy a life as possible, what is the effect of excessive weight on lifespan? Studies have shown that all-cause mortality is greater in people who are overweight or have obesity (The Global BMI Mortality Collaboration, 2016), so can the same be said for dogs?
Previous research has demonstrated an association between being overweight and reduced lifespan in a research colony of Labrador retrievers (Kealy et al, 2002), but, until recently, nothing similar had been reported either for pet dogs or for dogs from different breeds.
In newer research, an association between overweight body condition and a shorter lifespan was identified in pet dogs of various breeds (Salt et al, 2018). The study was retrospective, with a case-control design, and examined the electronic medical records from dogs registered with a North American veterinary hospital network comprising 900 veterinary hospitals.
More than 50,000 dogs from the 12 most popular breeds, aged between 6.5 years and 8.5 years, were identified as being in “overweight” or “normal” body condition. The electronic medical records were used to calculate lifespan in each dog.
Overweight body condition was associated with a shorter lifespan, although the impact varied among breeds, with the greatest reduction seen in dogs from the smallest breeds. Although further work would be needed, the fact the negative impact of overweight body condition was seen in all 12 breeds studied suggests a similar effect is probable in other breeds and in dogs of mixed breeding.
The study had an observational design and, as a result, was not designed to explore possible reasons for the association between overweight condition and lifespan. One explanation is that overweight body condition predisposes to one or more comorbidities that have the potential to shorten life – for example, neoplasia (Glickman et al, 1989; Lund et al 2006; Sonnenschein et al, 1991) or prompt an owner to consider euthanasia (for example, severe OA leading to immobility).
An alternative explanation would be that weight status is a proxy measure for caloric intake, since caloric restriction without malnutrition is known to extend lifespan in other species, including spiders, fish, invertebrates and rodents (McCay et al, 1935; Weindruch, 1996).
In primates, dietary caloric restriction can also counteract the impact of diseases of ageing (Weindruch, 1996), although the strategy has not yet been conclusively shown to extend lifespan (Colman et al, 2009; Heilbronn and Ravussin, 2003; Lane et al, 1998; Mattison et al, 2012).
Further, biomarkers associated with ageing (including fasting body temperature and fasting blood insulin) decreased as a result of prolonged caloric restriction (Heilbronn et al, 2006). Possible mechanisms behind the beneficial effect of caloric restriction include reduced production of reactive oxygen species, decreased subclinical inflammation, or alterations in insulin sensitivity, neuroendocrine function or stress responses (Colman et al, 2009; Heilbronn and Ravussin, 2003; Weindruch, 1996).
A further question that requires additional study is the reason why overweight status had different effects on lifespan in different breeds. As previously mentioned, the average reduction in lifespan was greatest in dogs from the smallest breeds (for example, a 2.5-year average reduction in male Yorkshire terriers) and least in dogs from the largest breeds (5 months in male German shepherd dogs).
Possible reasons for such breed variation may include differences in predisposition to comorbidities. For example, OA is more common in larger breeds than smaller breeds (Bland, 2015). Alternatively, individual breeds may be more or less well equipped to cope with the functional impairments that result from being in overweight condition – for example, effects on mobility, respiratory function and insulin sensitivity.
Whatever the reasons, the significance of this lifespan effect should not be ignored. Indeed, even in the breeds where the effect was least pronounced, such shortening is likely to be significant for the owner of a beloved dog.
Could this be the message that really makes an impact with owners and convince them of the need to implement a controlled weight loss programme?
Lifespan is something most clients can comprehend more readily than future disease risk or even their pet’s quality of life. The thought of less time to spend with their canine companion may help to focus the mind on making a positive change.
If your client heeds your advice, what are the next steps? For overweight adult pets, even losing a modest amount of weight, in the region of 6% to 9%, can improve mobility (Marshall et al, 2010); such a change can happen quickly and typically within the first two months of a weight loss programme (German, 2016a). Implementing a formal programme is usually preferred, since it provides the best support for owner and pet in the weight loss journey.
Although the current research did not explore this, it is likely the greatest increase in lifespan would be seen in those that maintain an optimal body condition throughout their life. Achieving this requires a lifelong prevention strategy, so how may you achieve this?
For puppies and young dogs, a formal growth monitoring programme is recommended, and validated evidence-based growth charts are now available for this purpose (Salt et al, 2017). These can be downloaded free of charge and are ideal for introducing as part of your practice puppy pack (www.waltham.com/resources/puppy-growth-charts). Male and female charts are available for dogs in five size classes.
Each chart has a series of curves (also known as “centile lines”) that depict the typical growth pattern within that category. Puppies can be weighed monthly in the first six months of life, and then every two to three months, with the resulting data used to plot the pattern of growth on the chart (Figure 1).
Corrections (for example, in amount fed) can be recommended when puppies are found to be growing too rapidly, crossing centile lines in an upwards direction on the chart. Addressing any under-growth or over-growth issues during this critical early phase is the best route to set a dog on the path to healthy weight for life.
Once a dog has reached skeletal maturity in optimal body condition, a preventive bodyweight monitoring programme will help to keep it that way. The “early adult optimal bodyweight” (for example, a weight taken at 18 to 24 months, with the dog verified to be in ideal body condition) should be formally recorded in the clinical records and used as a reference for future bodyweight.
Dogs should then be weighed at least every six months throughout most of their adult life, until the senior phase when three-monthly is recommended (German, 2016b). Deviations of 5% or more from the early adult optimal weight should be flagged and used to prompt discussions with owners.
Such a proactive strategy enables subtle weight gain to be identified quickly and then corrected – for example, with small adjustments in food intake.
Evidence is available of an association between overweight body condition and shortened lifespan in pet dogs, providing further evidence of the adverse impact this chronic disease has on health.
It is hoped this will be a motivator for veterinary professionals to start addressing the difficult topic of obesity with dog owners and implementing programmes that can improve their quality of life. There is no better time to start promoting a leaner, healthier and potentially longer life for our four-legged friends.
