Introduction

Obesity is defined as an accumulation of excessive amounts of adipose tissue in the body. In humans, strict definitions of the degree of adiposity exist, and these are based upon epidemiological data. Overweight dogs are greater than 15% above their ideal weight, whilst the term obese is used when current weight is 30% above ideal. Disease associations have been proven for companion animals that are both overweight and obese. Certain behaviours are known to predispose to weight gain and obesity whilst behavioural modification has been found to be beneficial in facilitating weight loss.

Causes of Obesity

The main reason for development of obesity is an imbalance in the 'energy balance equation', in that either excessive dietary intake or inadequate energy utilisation cause positive energy balance leading to increased body fat stores. Numerous factors may influence the relative ease with which weight is gained, and these include genetics, age, neuter status, amount of physical activity, and the caloric content of the diet.

Influencing Factors

It is known that a number of canine breeds are predisposed to develop obesity e.g., Labrador retriever, Cairn terrier, Cavalier King Charles spaniel, Scottish terrier, cocker spaniel. Neutering is also an important risk factor by causing behavioural changes, which can lead both to an increased food intake and decreased activity. Gender itself is also a predisposing factor in some canine studies, with females over-represented. Other recognised associations in dogs include indoor lifestyle, inactivity, and middle age. Dietary factors can also predispose to obesity with both the number of meals and snacks fed and the feeding of table scraps being key. Behavioural factors also play a part in the development of obesity.

Lifestyle Alterations for Obese Patients

Alterations in lifestyle include changes designed to increase energy expenditure (e.g., increasing level of physical activity, introducing regular play sessions), improve quality of life and effect changes in feeding patterns to fit more closely with the natural behaviour of the species concerned. The aim is to maximise the animal's ability to utilise its nutritional input effectively (e.g., accurate measuring [and recording] of daily food intake, avoiding uncontrolled feeding of extras and considering behavioural factors). In humans increasing physical activity is a useful adjunct to weight loss through other means (diet or pharmaceutical) and when used in combination with dietary therapy, promotes fat loss and may assist in lean tissue preservation. There is also some evidence that exercise may help prevent the rapid regain in weight that can occur after a period of successful weight loss.

The exact exercise programme recommended must be tailored to the individual, and take account of any concurrent medical concerns. It should also take account of existing capabilities, breed and age of the patient, as well as the age, health and other conditions of the owner. The aim should be to increase the level of activity in gradual steps and to make it a regular feature of the pet's life. The type of physical activity recommended will vary depending upon the individual; suitable exercise strategies in dogs include lead walking, swimming, and the use of a treadmill.

Overview of the Behavioural Approach to Obesity Management

A behavioural approach is particularly valuable when considering the lifestyle alterations that have already been discussed and by reflecting on the natural canine behavioural patterns we can offer relevant and practical advice to owners.

Natural canine behaviour determines such issues as food selection, consumption and protection but the domestic environment puts constraints on these natural behaviours and influences feeding patterns.

The Influence of Anxiety on Feeding Behaviour

Anxiety acts as an appetite depressant and dogs that are suffering from chronic anxiety and are experiencing unavoidable stressors may show variations in appetite over time.

In the absence of physical illness, over eating, under eating and noticeable fluctuations of eating may all be indicative of emotional instability.

The Influence of Perceived Value of Food Resources on Defensive and / or Competitive Behaviour

The social significance of canine feeding behaviour and the influence of group structure on the availability of food to individuals have been well documented - but what does that mean in practical terms? So called practical "dominance reduction programmes" will often concentrate on feeding behaviour. Advice is given to feed the "lower ranking" dog after the "higher ranking" humans and in some literature bizarre rituals of humans pretending to eat dog food are even advocated. The theory is that, when humans are giving food to dogs on demand, this can give the wrong message to the dog in terms of its "status within the pack" but the true social significance of timing of feeding has not been explored and there is no evidence to support the advice. Indeed studies suggest that wild dogs will allow those individuals who have greatest need to eat first irrespective of age or relative levels of confidence. It is therefore highly unlikely that the order of access to food is important in terms of any social struggle between owner and pet but teaching dogs to wait in order to gain access to such a highly valuable resource is beneficial through increasing consistency and predictability in the environment and thereby reducing anxiety. It can also help to improve expectation over access to food resources and prevent problems of frustration when access is denied. However, the practice of insisting that dogs perform complex tasks or wait for extended periods of time in order to be granted access to the essential resource of nutrition may increase negative emotions, such as frustration, and be detrimental to the animal in both a physiological and an emotional sense.

The Influence of Time Budgets on Food Intake and Weight Control

Weight is determined not only by food intake but also energy consumption. In the wild the location, seizing and dispatching of prey consumes energy and dogs may travel large distances in search of prey and take considerable time to do so. In the domestic environment dogs are often fed highly palatable, energy dense food and this food is fed in a manner that involves minimal energy expenditure. The time taken to consume food on a daily basis is also minimal. It is possible to increase the time spent feeding by using puzzle feeders and part of the behavioural approach to obesity cases will involve looking at delivery methods for daily nutrition.

The Influence of Behavioural Factors Such as Social Behaviour on Food Intake and Weight Control

Dogs value food as a social facilitator and therefore they are highly susceptible to overfeeding and problems of obesity. The influence of the use of food as treats and the feeding of human food is highly significant in canine obesity cases.

The Influence of Human Perception on Food Use in the Dog - Owner Relationship

Humans use the delivery of food as a means of demonstrating affection and this can also lead to emotional conflict for dogs. Dogs in emotional conflict become anxious and as a result of their emotional state unwanted behaviour, such as begging may develop. When dogs are anxious they need more information to make sense of their environment. They ask for this information through appeasement behaviours which are often interpreted as attention seeking. Many owners worry about rejecting their dog's attention and instead they respond to it by cuddling the dog and giving it affection. Whilst the affection is being given the dog feels secure but as soon as the affection stops the attention seeking begins again. After a while the attention seeking becomes annoying and now the owner may respond in one of two ways. They may reject the dog and isolate it from the room or they may respond by offering the dog a food treat to keep it happy. Either of these reactions runs the risk of complicating the emotional state of the dog further.

Begging as a Learned Response

When owners respond to "begging" by giving food their action results in food being perceived as a reward and the dog learns that intense appeasement behaviour results in the arrival of food. This leads to positive reinforcement and an increase in both the intensity and the persistence of the behaviour. In order to reduce begging behaviour it is necessary to reduce underlying anxiety.

In most cases dogs started the appeasement process because they were seeking social reassurance and information. Increasing consistency and predictability can reduce anxiety and thereby reduce unwanted appeasement and decrease the use of treats.

Food Is Not the Only Possible Reward

When rewards are needed other options such as play, exercise and social interaction can be used and introduction of non-food related rewards should start as early as possible. It is important to remember that is often the owner who wants to use food rather than the dog that really requests it.

Conclusions

The approach to obesity in companion animals needs to involve more than simply changing the animal's diet or influencing its food intake pharmacologically.

Other factors include:

 Ensuring a correct balance between energy input and expenditure.

 Considering the behavioural dynamics between animal and owner.

 Investigating individual factors relevant to each animal including medical and behavioural disorders.

Owners need to find ways to maximise their pet's calorific output and establish self-control of food intake. Physical exercise and mental stimulation are both important aspects of this behavioural approach. Maximising these activities decreases the risk of behavioural disorders associated with anxiety and insecurity, and helps to maintain a healthy balance between energy input and expenditure.

Obesity is a matter of great concern for the pet population. It is a medical condition with serious welfare implications and successful treatment relies on a combination of behavioural therapy, lifestyle management and diet control.