Obesity is one of the most common health problems affecting the pet dog and cat population, with an estimated 34–59% of dogs (McGreevy et al, 2005; Lund et al, 2006; Courcier et al, 2010a) and 25–39% of cats (Scarlett et al, 1994; Lund et al, 2005; Colliard et al, 2009; Courcier et al, 2010b) being overweight or obese. The most common and clinically applicable method of diagnosing obesity is a body condition scoring (BCS) system (Figures 1 and 2). A nine-point, five-point, or lettering system can be used, as long as all staff within a clinic are using the same system consistently. BCS should only be used to assess body fat, while muscle condition scoring should be used to quantify muscle wasting (for example, an obese pet, with a BCS of nine on a nine-point scale, could also have severe muscle wasting) (Figure 3). Each BCS is generally defined as a 10% increase or decrease from ideal bodyweight. While definitions of obesity vary overweight is generally considered 10–20% above optimal bodyweight (BCS of six to seven) and obese as 20% or more above optimal bodyweight (BCS of eight to nine). Bodyweight, BCS, and muscle condition scoring are a standard part of every physical examination and should be documented in the record at every visit.
Consequences of obesity
Obesity has been associated with numerous diseases, including pancreatitis (Hess et al, 1999), osteoarthritis (Kealy et al, 2002), dermatologic disease (Scarlett et al, 1998), diabetes (Scarlett et al, 1998), certain types of neoplasia (Perez-Alenza et al, 1998; Weeth et al, 2007), and respiratory tract disease (Bach et al, 2007). In addition, obesity may contribute to a shorter lifespan. In a lifetime study, a group of Labrador retrievers maintained at a median BCS of four to five on a nine-point scale lived a median of 1.8 years longer than a control group maintained at a median BCS of six to seven on a nine-point scale (Kealy et al, 2002). Obesity in all species is more easily prevented than treated and the veterinary nurse plays an important role in educating clients before the pet becomes obese.
Clinical considerations
Owners with financial concerns should be made aware of the increased costs associated with having an overweight pet, which can include food, preventa-tive care, medications and associated comorbidities. Irrespective of finances, obese patients require special clinical consideration. Obese patients undergoing anaesthesia may be at higher risk and should be monitored carefully. Drug dosages are particularly of importance in medications with a narrow safety range, such as some chemotherapeutics and im-munosuppressive medications. Calculating requirements based on obese bodyweight may increase risk of side effects, while using optimal weight is more subjective and could potentially lead to decreased ef-ficacy. Each patient and medication must be considered on an individual basis. While studies in human medicine have started assessment of this problem (Soler et al, 2009), more studies are needed in veterinary medicine to determine the most efficacious way to adjust bodyweight and dose medications.
Prevention
A discussion of proper feeding and body condition is an important part of initial puppy and kitten visits. Owners should be instructed to meal feed their pets to achieve an ideal body condition, rather than free feed. This is particularly important for large breed puppies, where a BCS of four on a nine point scale has been shown to be ideal (Kealy et al, 2002). A lower calorie puppy or kitten food should be selected if needed rather than switching to an adult food to ensure all essential nutrients are provided during growth. In many pets, energy requirements decrease after spaying or neutering (Hoenig and Ferguson, 2002), so it is important to let owners know and monitor their pets' intake. The same applies to yearly visits, where proper bodyweight and condition should be reinforced. Adult as well as growth feeding directions, even on foods marketed for weight management, can grossly overestimate a cat or dog's energy requirements (Linder and Freeman, 2010), so owners should continue to feed to an ideal body condition.
Weight loss plans
Cats and dogs that require severe caloric restriction or have a large percentage of weight to lose will likely need a veterinary therapeutic diet formulated for weight loss. Simply restricting the amount fed of over-the-counter maintenance diets (including those marketed for weight management) may risk restricting essential nutrients in addition to calories. This can potentially lead to loss of lean body mass or risk of nutrient deficiency, even if it is not clinically noticeable.
Initial assessment
A complete diet history should be obtained to allow for an accurate estimate of daily caloric intake (Table 1). Many owners are not aware that supplements, treats, rawhides or dental chews contain calories, so these should specifically be asked about. If current intake can be estimated, then calories should be restricted to 80% of current intake initially. If current intake cannot be determined, caloric restriction should start at the calculated resting energy requirement (RER: 70 × BW(kg)0.75) for estimated ideal weight and then be adjusted accordingly. More important than the starting amount are weekly or biweekly weigh-ins to ensure safe and effective weight loss.
|
|
Diet selection
Weight loss diets should be selected that contain an increased nutrient:calorie ratio and have been formulated for weight loss. Over the counter ‘light’ or ‘weight management’ diets are often not ideal for weight loss as they vary considerably in calorie density (Linder and Freeman, 2010) and may not contain adequate amounts of protein and other essential nutrients when restricted to the amounts necessary to achieve weight loss. The optimal nutrient profile for a weight loss diet should be based on the preferences and lifestyle of the owner and the pet. Compliance is critical in weight management, so paying particular attention to owners' concerns will increase success.
Lower calorie density
Two methods for reducing calorie density include added moisture and added fibre. Wei et al (2011) showed decreased voluntary intake and bodyweight in cats fed ad libitum with increased dietary water content. This may differ for each pet and may depend on financial considerations as well (canned foods can be prohibitively expensive in a large breed dog). Studies on fibre and satiety have been conflicting, with some claiming increased satiety (Jewell et al, 2000; Weber et al, 2007), while others have shown no benefit (Butterwick and Hawthorne, 1998; Yamka et al, 2007). While many cats and dogs do well on high fibre diets, some may have gastrointestinal side effects (vomiting, diarrhoea). Patients should be tran-sitioned gradually to the new food over a week and owners should also be warned of a potential signifi-cant increase in faecal volume.
Macronutrient profile (protein, carbohydrates, and fat)
The majority of weight management foods have a lower fat content to help reduce caloric density. Increased protein may have a role in satiety (Weber et al, 2007), but more importantly, it has been shown to help retain lean body mass during weight loss (Laflamme and Hannah, 2005). This is most likely due to the increased protein intake reducing the need for animals to break down their own muscle. It has been suggested that higher carbohydrate diets lead to obesity in cats, however, experimentally, high fat diets have been shown to be more of a concern for obesity development than high carbohydrate diets when free-fed (Backus et al, 2007). Luckily, there are weight loss diets with a variety of nutrient profiles available for cats.
Dietary additives
Some weight loss diets have added carnitine, a co-factor in fat metabolism, or omega three fatty acids. There are currently no known adverse effects to supplementation, although further research is needed before widespread supplementation can be recommended.
Treats
If owners feel treats are important, compliance may be increased by allowing treats, but should be limited to 10% of the total calorie intake. Some examples of low calorie treats include non-starch vegetables such as carrots or celery. Alternatively, a small portion of the daily allotment of food can be given throughout the day as treats.
Exercise
For dogs that are able, exercise is an integral part of a weight loss programme. Increasing physical activity will allow dogs to ingest slightly more calories while maintaining weight loss goals (Wakshlag et al, 2012). Owners should be encouraged to increase their pet's activity gradually and walking or swimming can be great activities for previously sedentary dogs. For dogs with orthopaedic disease, there are an increasing number of veterinary physical rehabilitation services available that can help improve strength and mobility while limiting the risk of further injury. Encouraging exercise in cats can include food dispensing toys, feeding multiple small meals in differ-ent parts of the house, hiding kibble around a room or throwing it down a hall to be fetched, feather toys, laser pointers, and electronic mice.
Follow up
The single most important aspect of weight management in dogs and cats is follow up. At the first weigh-in, dogs or cats may stay the same or gain weight initially. Prepare owners that this is a trial period to assess what their pets' actual energy requirements are. Food amounts should be adjusted until 1% body weight loss per week is seen. This will limit risk of nutrient deficiency, loss of lean body mass, and rebound weight gain (Laflamme and Kuhlman, 1995). For some cat owners, purchasing a baby scale to avoid frequent stressful trips to the veterinary clinic may prove useful. It is not uncommon for pets to eventually plateau in their weight loss. Owners can easily get discouraged, but continue to adjust the food as needed or increase exercise to continue weight loss.
Exceptions to the 1% weekly weight loss include dogs and cats with comorbidities where a more gradual rate of loss (0.5%) is recommended. Additionally, cats often decrease their energy requirements signifi-cantly when faced with caloric restriction (Villaverde et al, 2008). This often leads to further restriction in caloric intake to continue to achieve weight loss, which may increase risk for inadequate intake of nutrients. Veterinary therapeutic weight loss diets may be even more important in these patients where the rate of weight loss or level of caloric restriction is a concern.
Once ideal weight has been reached, the majority of cats and dogs will continue to need caloric restriction. Reinduction of obesity occurs much more easily and faster with pets that have previously been overweight (Nagaoka et al, 2009), so lifelong monitoring of caloric intake is required in most cases.
Psychology of obesity
While some argue obesity should be considered a medical disease, others argue it is solely a psychological disease of the owner. The complex relationship between owners and their pets must be understood in order to achieve successful weight loss. A recent epidemiologic study on the risk factors for canine obesity found only owner-related factors in their final analysis, including owner age, frequency of treats, amount of exercise, and income, which was also associated with lower awareness of health risks associated with obesity (Courcier et al, 2010a). Educating owners on obesity, health consequences, and appropriate feeding is an initial step in a weight loss plan. In two separate studies, 39% of owners underestimated their pet's BCS, even after being told what their veterinarian determined their pet's BCS to be (Rohlf et al, 2010; White et al, 2011). Even more concerning, Bland et al (2009) showed that half of the owners who correctly identified their pets' BCS score above optimal still did not consider their pet to be overweight.
Beyond acknowledgement of BCS, owners should also be educated on appropriate feeding methods. Many owners do not measure their pets' allotment of food and may be giving much larger serving sizes than they are aware of. Over or under-filling a measuring cup can also lead to problems, with German et al (2010) showing staff from a veterinary hospital ranged from 18% less to 80% more than intended based on inaccurate feeding methods. For households with multiple owners or cases where small differences in calories could make a difference, weighing the food on a home scale and pre-packaging into portions increases compliance. In addition, smaller scoops and smaller dog food bowls may be of use in weight loss cases, as Murphy et al (2012) showed owners tended to portion less than their intended amount with varying scoop and bowl sizes.
While owner education seems the logical way to combat obesity, Yaissle et al (2004) have shown that having owners participate in a monthly class on nutrition and obesity was not enough, and did not increase weight loss over a control group with no education, though both groups were closely monitored with extensive follow up. While this may sound discouraging, it simply adds to the growing notion that pet obesity is a multi-factorial, highly complex condition that requires intensive and active efforts on both the owner and veterinary staf's behalf.
Conclusion
Obesity is a common condition in cats and dogs and can lead to serious health consequences. Prevention of obesity is best done by educating owners and assessing body condition during growth and at yearly wellness visits. When a patient is overweight, thorough assessment of the current diet, potential challenges, and concerns of the owner is necessary to form a successful weight loss plan. Feeding a purpose-formulated diet with an increased nutrient:calorie ratio is recommended in most cases to achieve a gradual 1% weekly rate of bodyweight loss. Follow up with patients, adjusting the programme, and working with owners to increase compliance is crucial for successful weight loss.