Introduction

Obesity is a clinical syndrome that refers to the excess accumulation of body fat. Obesity is considered to be the most common form of malnutrition in small animal practice. It has been suggested that as many as 40% of pets are obese. The significance of obesity pertains to its role in the pathogenesis of a variety of diseases and the ability to exacerbate pre-existing disease. Obesity has been associated with an increased incidence of arthritis, cardiorespiratory problems, diabetes mellitus, constipation, dermatitis, anesthetic risk, and reduced life-expectancy.

Causes of Obesity

Obesity develops when energy intake consistently exceeds daily energy expenditure. Undoubtedly there are numerous environmental and social factors that contribute to the formation of obesity. These include decreased daily exercise as a result of confinement to the house and overfeeding of the pet by the client. Ad-libitum feeding of highly palatable diets may predispose to overeating. Snacks and treats contribute to excess daily caloric intake. Breeds including the Labrador Retriever, Cairn Terrie, Collie, and Basset hound seem to have an increased likelihood of obesity. Additional risk factors for obesity include age (increased risk with aging), sex (females have higher risk), and neutering.

Obesity is less likely to result from a disease process or drug. Endocrine abnormalities associated with obesity such as hypothyroidism and hyperadrenocorticism. Drugs such as the progesterones, used for contraceptive management, have been associated with the development of obesity.

Techniques to Determine Obesity

Obesity is defined by an excess accumulation of body fat. Techniques to assess the degree of body fat include morphometric measurements, dilutional techniques, bioelectrical impedance analysis, dual energy x-ray absorptiometry, densitometry, computed tomography, magnetic resonance imaging, total body electrical conductivity, total body potassium, and neutron activation analysis. Unfortunately, many of these techniques are not clinically applicable.

Body weight is the simplest technique available and should be included in the examination of every patient. It provides a rough measure of total body energy stores and changes in weight parallel energy and protein balance. However, edema and ascites may mask losses in body fat or muscle mass. Likewise, massive tumor growth or organomegaly can mask loss in fat or lean tissues such as skeletal muscle.

Body condition scoring (BCS) provides a quick and simple subjective assessment of body condition. Different scoring systems have been described but the most common scoring system used is a 5-point system where a BCS of 3 is considered ideal or a 9-point system where a BCS of 5 is considered ideal. The technique of body condition scoring does depend on operator interpretation and does not provide any precise quantitative information.

Management of Obesity

The management of obesity requires clinical identification of either those dogs that are obese or, just as importantly, those dogs that are at risk of obesity. Once this has been determined, a thorough dietary history should be obtained. Information that should be gathered includes:

 The name, manufacture and type (i.e., canned versus dry) of the current diet

 The amount of diet that is fed each day (can versus cups of food)

 The method of feeding (ad-libitum versus meal fed)

 The person responsible for feeding the dog

 Additional persons that may fed the dog (especially children, elderly parents or friendly neighbors)

 The number and type of snacks or human foods given each day

 Access to foods for other pets

This dietary information should be used to calculate the daily caloric intake of the dog. The dog's current body weight should be recorded, and the target body weight of the dog should be calculated. Ideally, the initial target body weight should be 15% of the current body weight. It is very important to set realistic and obtainable goals for weight loss in order to maintain client compliance. New target body weights can be selected once the current target body weight has been achieved until the dog has an ideal body weight. The amount of calories to feed the dog is determined on the basis of the target body weight. If the amount of calories to achieve weight loss is actually less than the current daily caloric intake, the dietary history should be re-evaluated to search for additional calories. If no additional daily calories are identified, then the daily caloric intake of the dog should be reduced by 15%.

Once the daily caloric requirement to achieve 15% body weight has been calculated, consideration should be given to the type of diet to feed. There are essentially two main dietary options, either feed a reduced amount of the regular maintenance diet, or feed a diet that has been specifically formulated for weight reduction. It is not advisable to feed less of the regular diet because this was the diet that lead to the problem in the first place. However more importantly, feeding a maintenance diet increases the risk of nutrient deficiency and unhealthy weight loss. Canine maintenance diets are formulated according to energy intake. This means that if a dog eats its daily energy requirement, it will automatically consume the required amounts of additional essential nutrients such as amino acids, vitamins and minerals. By feeding less of the maintenance diet, you are not only reducing the amount of energy, but also are reducing the amount of protein, vitamins and minerals, and thereby may risk malnutrition. Conversely, diets that have been specifically formulated for weight reduction have been formulated such that they contain more essential nutrients relative to the energy content of the diet. This means that they will receive the required amounts of proteins, vitamins, and minerals, even thought they are ingesting less energy.

Diets formulated specifically for weight reduction will vary according to the fiber and protein content. High fiber diets have been suggested for weight loss because fiber may provide a satiating effect. High dietary fiber content will reduce the digestibility of the diet, increases the amount of fecal material and increases the amount of water lost into the feces. High protein diets have been reported to increase the proportion of fat loss while preserving or indeed increasing the lean body mass. The lean body mass is the most metabolically active portion of the body and includes skeletal muscle tissues. Preservation of lean body mass has been shown to facilitate successful long term maintenance of ideal body weight once weight loss has been achieved.

Carnitine is an amino acid that is vital for energy metabolism. Carnitine facilitates the movement of long chain fatty acids across the mitochondrial membrane were the long chain fatty acids can be used for energy production. Carnitine supplementation may facilitate fat loss and maintain lean body mass.

Ideally, the dog should be meal fed rather then fed ad libitum. The number of feedings per day can be selected to suit the clients' schedule, but 2-4 meals per day is adequate. One member of the household should be selected to feed the dog. This will reduce inadvertent over feeding by additional family members. The owner should be instructed to either eliminate treats completely, or if this is met with resistance, instructed to limit the number of treats to less than 10% of the daily caloric intake. Ideally, low calorie treats should be selected. The behavior of the owner should also be altered by not allowing the dog into the kitchen or dining room during meal preparation or eating. This will reduce the likeliness that the client will give the dog human snacks which are generally high in calories. In addition, the client should inform and enlist the support of both family members and neighbors to the weight reduction program so that they do not unknowingly give the dog additional calories. In some cases, it may be useful for the client to utilize a food diary to record the amount of food and snacks fed each day. For other clients, this technique is often met with resistance and should not be considered.

In addition to reducing the daily caloric intake, every effort should be made to increase the daily energy expenditure by encouraging exercise. This could be in the form of walks or, if the dog has concurrent arthritis, swimming.

Dogs on weight reduction programs should be reevaluated every two to four weeks. Body weight, and body condition score should be recorded. The dietary history should be reviewed. Ideally, the dog should achieve about 1-3% body weight loss per week.

Prevention of Obesity

The key to obesity management is prevention. Energy requirements decrease when the animal is spayed or castrated. Therefore, prevention should begin at the time of neutering. Owners should be counseled about the risk factors of obesity (age, sex, breed, life-style, inappropriate feeding practices), and the consequences of obesity. Importantly, owners should be instructed on both how to feed their dog, and how to regularly determine body condition such that they can maintain ideal body condition of their dog. The importance of optimal body weight control should be reinforced at each annual health examination.

References

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