Pet obesity: new challenges, new solutions

Introduction

Obesity can be defined as “a disease in which body fat has accumulated to the point that the health of an individual is adversely affected” and – in both pets and humans – it is associated with negative effects on wellbeing and health, a shortened lifespan and a poorer quality of life. Despite much recent scientific and media interest, the prevalence of obesity continues to increase, and the problem shows no signs of abating 1,2. This article considers the current challenges with pet obesity before looking at possible options that may help improve the management of this chronic disease.

What are the challenges?

Increasing overall prevalence of obesity

Numerous studies over the last 30 years have reported the incidence of obesity in pets, and although comparisons between studies should be made cautiously, there is an apparent trend towards an increasing prevalence in both dogs and cats. In studies using a body condition score (BCS) of 1 to 9, the number of dogs rated as 8/9 or 9/9 increased from 10% in 2007 to 19% in 2018, and for cats in the same period from 19% to 34% 2.

Increased prevalence in growing animals

There is an even more concerning trend in growing animals. A recent study reported the prevalence of overweight and obesity in cats at 12-13 months of age to be 7% 3 – which may be an underestimate, given that this employed data from owners (rather than veterinarians) on weight status. More concerning is the situation with young dogs; one study found that of 516 juvenile (< 24 months) dogs, 190 (37%) were either in overweight or obese body condition, with the prevalence increasing steadily during the growth phase, from 21% (21/100) in dogs under 6 months of age to 52% (16/31) in dogs 18-24 months of age 4.

Changing breed popularity

Recent changes in demographics, with the increased popularity of small-breed (particularly brachycephalic) dogs are also significant. Historically, it was typically medium-to-larger breed dogs that were predisposed to obesity, but a recent survey 2 noted the greatest prevalence was now mostly in small and toy breeds of dog (Figure 1).

Owner assessment

Owners often underestimate the true body condition of their pet, assuming them to be slimmer than they are. This may be because their overall perception of body shape is incorrect, or it may be that their assessment is linked to constant exposure to overweight and obese pets, and exacerbated by media images that depict animals perceived to be “perfect” examples of their breed; for example, in a recent observational study 26% of animals photographed at a national dog show were judged overweight 5. This might explain why veterinary and owner estimations of body condition can differ, and why owners can distrust professional assessments regarding obesity 6.

Increasing number of animals “beyond the scale”

Of major concern is the fact that whilst the 9-point BCS scale is useful, 9/9 depicts an animal that is 40% above its ideal weight, but this arguably does not reflect the degree of adiposity seen in the current generation of pets (Figure 2), many of which are now “beyond the scale”. A long-term survey has noted an average of 46% of patients to be > 40% above ideal weight (author’s unpublished data), with the most recent years (2015-2020) showing 59% of animals to be past this marker.

Efficacy of weight management protocols

Given the negative correlation between the percentage of body fat mass and the success of weight management programs, there is a significant challenge with returning obese pets to their ideal weight. Some professionals have claimed that weight management is easy 7, but this is a misperception, perhaps because many early studies were often in colonies where the dogs were young, healthy and often only modestly (< 20%) overweight, and where owner influence was absent. Such studies are not typical of pets with obesity, and more recent research has shown that even with marked dietary energy restriction the rate of weight loss is typically less than 1% per week 8,9. The reasons for this include a more variable pet population (in terms of age, neuter status and breed), the fact that pets are often very severely overweight, and often have comorbidities 10. However, owner factors, such as the feeding of table scraps and treats, are also important 9. This suggests that, in contrast to the findings from colony studies, achieving weight loss in obese pets is extremely challenging.

The figures for overall success in dieting schemes are often disappointing. In one study only 53% of dogs with obesity enrolled in a 6-month weight loss program completed the course, and educating owners about nutrition made little difference 8. In a second study examining compliance with weight management 10, 61% of dogs successfully reached their target weight, whilst in a similar study in cats with obesity, just 45% reached their weight goal 11. A key factor associated with success or failure is the severity of the obesity, i.e., the greater the body fat mass, the more likely it is for the animal to fail to complete the program. Importantly, attrition from a weight program is not uniform; compliance is usually good in the first 12 weeks, with >80% of animals still enrolled and averaging over 8% of body weight loss (Figure 3), but very few will have reached their target weight in this period and more will discontinue the program in subsequent weeks.

A further challenge is the fact that many animals will subsequently regain weight. In recent studies, 48% and 46% of dogs and cats respectively regained weight after successfully reaching their target 12,13. This is disappointing and emphasizes that managing obesity is a lifelong process which provides a major challenge to pet owners.

So a combination of slow percentage of weight loss, poor completion rate and risk of subsequent weight regain underlines the fact that successful weight management is testing, and that in reality only a minority of pets on a program will ever reach their target. However, most concerning is the fact that few dogs and cats with obesity ever undergo any sort of weight management at all. It is estimated that over half of all pet dogs and cats are either overweight or have obesity 1 yet only 1.4% of veterinary health records mention the pet’s weight status 14. Given that so few veterinarians will formally identify this disease, it is unsurprising that weight management success is so poor.

Attitudes about obesity

When considering the cause of disease, society tends to assign “responsibility and blame” – i.e., those affected are either considered to be victims or perpetrators. So-called “disease stigma*” occurs when an individual is blamed for having a particular condition because of a moral or other failing 15, and this includes human obesity, with the predominant societal opinion being that people with the condition are personally responsible either because they are lazy, or because they overeat, or both. Recent research also suggests that such attitudes are used to justify weight discrimination, despite evidence that obesity is a complex chronic disease with multiple risk factors beyond the control of the individual 16.

* https://implicit.harvard.edu/implicit/selectatest.html

This weight stigma is also commonly found in many healthcare professionals 15, and the issue has recently been investigated within the veterinary profession. In one study, veterinarians admitted to using stigmatizing terms to describe excess weight in dogs, and reported feeling blame, frustration, and disgust towards both dogs with obesity and their owners 17. Veterinarians also expressed the belief that owners with obesity were responsible for causing obesity in their dogs, and were pessimistic about such individuals complying with treatment recommendations. There is also indirect evidence of weight stigma in other studies; for example, most veterinarians believe that “owner-related” factors are the main reason for development of obesity in pets 18. These opinions are at odds with the fact that multiple risk factors have been identified for companion animal obesity, including genetic factors.

There is an idea that weight stigma is positive, because it incentivizes people with obesity to lose weight – yet evidence actually suggests that it can negatively influence such individuals by decreasing their chances of successful weight loss, as well as affecting their mental health 19. It is tempting to speculate that weight stigma might affect the care that dogs and cats with obesity receive. Could these attitudes be associated with the fact that very few veterinarians record the terms “overweight” or “obese” in clinical records 14, and explain why they are reluctant to hold conversations with owners about obesity? In the opinion of the author, until we address the attitudes of veterinarians and wider society towards obesity – in both pets and people – we will continue to struggle to manage this disease effectively.

Where are the solutions?

Rethink weight management strategies

The author believes that the best strategy is to modify our approach, maximizing the benefits and minimizing the failures, in the hope of improving the quality of life of as many animals as possible. The first aspect is to consider the goals of weight loss. Currently, much of the focus is on the “numbers” – such as the ideal weight and the percentage or rate of weight loss. Instead, goals should relate to the benefits that weight loss can bring, such as improving metabolic health, mobility and quality of life. Prior to agreeing a weight loss plan, it helps to have an in-depth conversation with the owner regarding their concerns and priorities. For example, an owner may be worried that their dog has severe osteoarthritis, and their key priority is to improve its mobility. Here, rather than the outcome for weight loss being to lose a particular percentage of body weight, it should arguably be better mobility and less chronic pain, and the amount of actual weight lost is simply a path towards the overall goal.

Another consideration is knowing when failure in weight loss programs occurs. As explained above, compliance is typically very good in the first few weeks, with a reasonable rate of weight loss, typically ~1% per week (Figure 3); however, beyond this time the process becomes more challenging, with the rate of weight loss slowing and compliance issues setting in (Figure 4). Therefore, rather than designing a program to return a pet to its ideal weight, a standard “time-limited” protocol may be more useful. This can be likened to the use of chemotherapy, where a set procedure often involves standardized doses and timings, and a defined length of therapy. Outcomes are then reviewed at this time point, and further treatments and protocols are recommended accordingly. Weight loss programs could be approached in a similar way; 12 weeks is a sensible length for such a protocol, given that outcomes are best during this time irrespective of the amount of weight that the patient must lose, and the primary focus can be in helping the client to ensure completion. At this point the outcomes can be appraised, not just in terms of the weight lost but also by reviewing the health benefits that have been achieved. Agreement can then be made as to the next stage; this might be further weight loss, or a shift to weight maintenance, where the priority becomes preventing rebound.

There are many potential benefits of such an approach. Firstly, greater emphasis can be placed on factors that matter, especially for the owner, such as improvements in quality of life, with less focus on achieving a target weight. Reviewing the goals that have been agreed before the program commences (e.g., improved mobility, decreased use of analgesic medication for concurrent osteoarthritis) after 12 weeks can then inform the need for further cycles of weight loss. Secondly, a pre-defined endpoint gives better certainty for the owner in terms of what they are committing to – so although they may find the weight loss phase difficult, the end is always in sight. Thirdly, it maximizes the period when weight loss is most successful (which in turn maximizes compliance); and, finally, it recognizes that success is not determined by reaching a nominal “target weight” but rather that even modest weight loss can lead to improved quality of life. In this respect, studies have demonstrated that a loss in the region of 10% of the starting weight is possible during a 12-week period 20, and this is generally associated with notable improvements in mobility and quality of life.

Focus more on obesity prevention

Given that most dogs and cats never start a weight management program in the first place, veterinary professionals should place greater emphasis on obesity prevention. This has three main components, namely identifying “at-risk” individuals before obesity has developed, proactively monitoring at-risk individuals for life, and promoting maintenance of a healthy weight and lifestyle

Identifying “at-risk” individuals before obesity has developed

Using known risk factors (Box 1) to identify dogs and cats at risk of obesity enables preventive measures to be best targeted. Some of the most significant risk factors are as follows:

• Patterns of growth. In children, future risk of obesity is associated with certain patterns of growth, including rapid growth and catch-up growing, and a similar phenomenon has been reported in both cats 21 and dogs 22.
• Breed. This is particularly the case where obesity is more prevalent in certain breeds due to genetic influences (e.g., Labrador Retrievers, Golden Retrievers, Pugs). In cats, mixed-breed cats (domestic shorthair and longhair) are at greatest risk, with genetic factors also being a risk factor for obesity.
• Neutering. Neutering is an important risk factor in both dogs and cats, probably because alterations in sex hormones can lead to changed behavior, most specifically increased food-seeking and decreased physical activity. Because neutering is pre-planned, there should be no excuse for implementing prevention strategies afterwards.
• Comorbidities. Many other co-existing diseases can alter energy flux, either by increasing energy intake or decreasing expenditure, and these can predispose to inappropriate weight gain.
• Food and feeding behavior. There are varying opinions with respect to the associations between obesity and food, but arguably the most consistently identified risk is giving extra food in the form of table scraps and treats. In addition, certain feeding behaviors in cats are implicated as possible risk factors for obesity.
• Environment and activity. Animals living indoors (especially apartments) have a greater risk of developing obesity than those with outdoor access. Cats living either with dogs or with one or two other cats are also predisposed to becoming obese.
• Owner factors. A number of owner factors have also been implicated in the development of obesity in dogs and cats.

Box 1. Various risk factors that can predispose to excess weight gain and obesity in dogs and cats.

Proactively monitoring at-risk individuals for life

The above factors should enable a veterinary professional to determine an individual’s risk of obesity and allow best targeting of prevention strategies, and these should be implemented before the disease has developed (e.g., at or before 12 weeks of age), and continued for life.

A key strategy is to monitor bodyweight from the time of initial vaccinations, throughout the growth phase and into adulthood. Although BCS is a useful means of determining weight status in adult dogs, existing methods have not been properly validated in growing animals. Instead, monitoring of bodyweight, facilitated by the use of growth charts 23, can be useful. Evidence-based growth charts have recently been developed for puppies (https://www.waltham.com/resources/puppy-growth-charts), and their use can allow rapid identification of abnormal patterns of growth, not least those that are associated with the risk of obesity 24. Puppies should be weighed monthly until 6 months of age and then at least every 3 months until they reach adult weight. This maximizes the likelihood of a puppy reaching skeletal maturity in ideal body condition, and at this point the BCS can be used to confirm optimal condition, with the weight recorded in the patient’s health records as its “healthy weight”. The aim from then on is to ensure that this is maintained (to within ±5%) for the rest of the pet’s adult life. Ideally, animals should be weighed every 6 months, and no less frequently than once a year (i.e., at annual vaccination), but with more frequently weight checks introduced during the senior phase of life, for example every 3 months. Ideally, animals should attend the veterinary practice for weighing, since the same set of calibrated electronic scales can be used; in addition, body condition can be assessed, and any other minor health concerns addressed. However, where this is difficult (for example, with nervous cats), home weight checks can be employed coupled with phone consultations, with owners either using bathroom scales or luggage scales (e.g., weighing the cat in its transport box). However determined, the current weight should be compared against the pet’s healthy weight, and where a deviation of 5% or more is flagged, strategies can be implemented to help restore the healthy weight.

Promoting maintenance of a healthy weight and lifestyle

Various strategies can be used to prevent obesity in at-risk individuals, which broadly involve either controlling energy intake or increasing energy use.

• Controlling energy intake. This centers around the main meal offered. A nutritionally complete and balanced food should be fed, appropriate for the life stage of the animal. The choice is a matter for discussion between owner and veterinary professional, and the clinician is directed towards various reputable textbooks for further detail. Many pets exhibit strong food-seeking behaviors which owners often find difficult to refuse. In such cases, using foods with increased amounts of protein and fiber will improve satiety, thereby reducing voluntary food intake and food-seeking behaviors. Other strategies include decreasing the energy density of food by expanding its volume, either by adding water (or switching to a wet food if cost effective) or expanding a kibbled food with air. Finally, choosing a kibbled diet with a shape that requires more chewing will help slow food intake.

Whatever diet is selected, it is important to feed the correct amount, which will vary according to the food and life stage. This can be determined by calculating the pet’s maintenance energy requirements, or from the manufacturer’s guidelines, adjusted to individual circumstances (e.g., body weight, breed, sex, neuter status, activity level). The daily amount should be measured out accurately (see below) and fed for two weeks before reviewing. If weight has been lost in this time, food intake should be increased by 10%, or decreased by 10% if weight has been gained. Further cycles of weighing and adjustment should be continued until the body weight is stable. Thereafter, continue to weigh the animal at regular intervals to ensure that its weight remains on track.

• Accurate portion size measurement. Food portions must be measured out as precisely and accurately as possible, especially with dry diets, as their energy density means that even small over-estimates can mean significant overfeeding. Measuring cups to estimate the amount fed are simple but unreliable, leading to variable portion allocations and predisposing to overfeeding 9, so electronic scales are to be preferred (Figure 5). Accurate portion measurement should become easier in future with the development of “smart bowls” and computer-controlled food hoppers, which will automatically measure out the correct daily portion. Some devices may also monitor food consumption throughout the day, enabling owners to chart patterns of food intake and making it easier to spot disruptions which might indicate a health issue (Figure 6).

• Responsible feeding of additional food items. Although there is an association between the development of obesity and the feeding of additional food items such as table scraps and treats, owners are often unaware as to how much additional energy these food items contribute to their pet’s daily intake, so a prevention program should include control over this. If dry food is fed, part of the daily ration can be reserved and used as treats. If other food is involved, the amount should be limited to a maximum of 10% of the total daily calorie ration, with the main meal portion reduced accordingly.
• Method and pattern of feeding. Most dog owners, and many cat owners, feed their pet 1-2 meals per day from a bowl, but this allows for rapid consumption and consequently many hours without food, which can lead to hunger and increased food-seeking behavior. Some cat owners leave (usually dry) food out all day, either as an alternative to, or in addition to, meal feeding, but this is a known risk factor for the development of obesity. Veterinary professionals should recommend the use of puzzle feeders or modified feeding bowls which slow food intake; this can reduce the risk of over-eating (since the physiological “satiety signals” from the gastrointestinal tract take time to be released), and makes the feeding period last longer and more enjoyable for the pet.
• Increasing energy expenditure. Part of any prevention program will usually involve a review of physical activity levels, but in fact this only moderately affects an animal’s overall energy expenditure. On average, walking an extra 1000 steps only increases energy expenditure by approximately 1 kcal per kg^0.75, although there are other benefits, such as improving cardiovascular and musculoskeletal fitness and strengthening the owner-pet bond. The exact amount of physical activity should be tailored to the individual, and must take into account any concurrent medical concerns. For dogs, at least one daily walk of 30 minutes is recommended, but longer and more frequent is better, and extra play sessions can also be beneficial. If possible and safe to do so, allowing a cat access to outdoors is recommended, and they will also benefit from short play sessions, typically 1-2 minutes at a time at least twice daily.

Have better obesity conversations

Many veterinary professionals are reluctant to hold conversations about obesity with pet owners, possibly because it is a highly stigmatized condition. It is therefore important to tackle the issue of weight stigma within the profession and, in so doing, improve communication regarding obesity. Because weight stigma can be unconscious, a veterinarian may approach a case without being aware of the effect that this bias can have on the outcome, and it may be useful for clinic personnel to quickly check their own implicit weight bias 25. This may help with obesity management, for example by enabling the clinician to actively adjust both the advice they give to owners of pets with obesity and the way they communicate with them to ensure that their clinical recommendations are consistent. Indeed, a key aspect of addressing weight stigma is to focus on better communication with owners whose pets have obesity. Appropriate training is vital for such situations, and all conversations should be supportive and non-judgmental, using empathic non-stigmatizing terms. Care should be taken not to assign (or appear to assign) blame to the owner, as this is likely to be counterproductive, and “toxic” terms such as “obese” and “fat” must be avoided, since owners can find them uncomfortable and might be offended, which will do little to encourage them to address the issue. A “patient-first language” is recommended in human medicine, and a similar strategy can be used for pet obesity, so the choice of words is all-important. As the name suggests, the clinician should ensure that the patient comes first in the conversation, and should not refer to it as “being obese” or use phrases such as “an obese dog” or saying a dog “is obese”. One would not refer to a “cancerous dog” or say a dog “is cancer” so it is better to refer to a pet “with obesity” or say a pet “has obesity”. Although this change might appear to be trivial, this phraseology avoids labelling the patient.

Nonetheless, it can be tricky to find a way of introducing the topic during a consultation, not least if the owner has brought their pet for another reason (e.g., an unrelated illness or a routine vaccination). One strategy is to “talk about something else”, perhaps broaching the subject in terms of changes in weight and body condition. For example, if the clinic regularly records body weight (as discussed above in terms of obesity prevention), deviations from the animal’s “healthy adult weight” can be highlighted to the owner rather than discussing “obesity” – and again the choice of words is significant. Another strategy would be to use body condition (especially if BCS charts are displayed in the consult room) with the owner invited to assess their dog, along with guidance from the veterinarian. Talking about something else enables weight management to be discussed without ever using the term “obesity”, even though both owner and professional will know that this is the issue at stake.

However, it is raised, and prior to discussing the topic in terms of causes and solutions, it is sensible to consider first asking permission to ascertain that the owner is comfortable discussing the topic (e.g., “We have identified that Fluffy is currently above a healthy weight. Would you be comfortable with us discussing this and what we can do to help?”). Such a strategy emphasizes that the owner is in control and can facilitate acceptance of a weight management plan.

Classifying obesity as a disease

There have been recent moves to classify obesity as a disease, not least because it fits the formal definitions of disease 26. Although some argue that obesity is a normal physiological response to excess energy intake 7, there is significant scientific evidence to suggest that it is actually a pathological process, with over 20 national and international veterinary organizations supporting such a formal categorization. Classifying obesity as a disease may have a positive effect on how veterinary professionals manage pets with obesity – for example, when discussing causes of obesity, rather than only focusing on owner factors, the complexity of the disease pathogenesis can be emphasized, including other aspects such as genetic factors. This makes it easier for the clinician to be non-judgmental in their discussions with the client, thereby gaining their trust and increasing the chances that they will be receptive to weight management advice.

Conclusion

Pet obesity is currently a growing concern, with a changing picture in terms of the demographics of patients that are affected. Although weight management protocols are well-established, these are far from perfect and are often not even implemented by veterinary professionals. This is not helped by the fact that obesity is a highly stigmatized condition and often an awkward topic for discussion. Although there are no simple solutions, clinicians can be more effective in managing this problem, by considering short-term weight loss plans, by preventing obesity in young animals, and by more effective conversations about obesity. As with the human condition, formally classifying obesity as a disease could be a trigger to kick-start more supportive and effective obesity care from the veterinary profession.